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El objetivo de la presente revisión fue recopilar y discutir literatura científica sobre metodologías empleadas para la producción y elaboración del concreto innovador “concreto permeable”, como alternativa de diseño en pavimentos, con el remplazo parcial de agregado grueso por agregados reciclados, como látex de caucho al 5 % y 8 % por peso de cemento, ceniza volante entre el 0 % y el 70 % por volumen del cemento, y fibra de carbono al 0.27 % y 0.4 % por peso de agregado grueso. Esta revisión de literatura implicó seleccionar las publicaciones más relevantes, para los períodos del 2015 al 2021 en bases de datos indexadas Scopus, Scielo, ScienceDirect, y Latindex; enfocándose en múltiples parámetros como: “materiales residuales, coeficiente de permeabilidad, concreto permeable, grado de porosidad y ensayos de laboratorio para el concreto permeable”. Los resultados muestran que la resistencia a la compresión varía entre 0.5 MPa y 97.3 MPa, resistencia a la tracción entre 1.6 MPa y 5.29 MPa y la permeabilidad entre 4.63 mm/s y 10.2 mm/s, donde el porcentaje idóneo del uso de ceniza volante para la obtención óptima de concreto permeable es hasta el 20 %, que, excediendo este porcentaje, afecta negativamente sus propiedades mecánicas. En conclusión, el “concreto permeable” se sitúa dentro de los rangos establecidos según normativa: 17.5 MPa, 2.6 MPa, 6.1 mm/s, respectivamente; por ende, adquiere un valor sustancial, contribuyendo con la mejora del nivel microestructural y mayor durabilidad, siendo ventajoso y útil en los tiempos modernos.

Background: Continuous myelination of cerebral white matter (WM) during adolescence overlaps with the formation of higher cognitive skills and the onset of many neuropsychiatric disorders. We developed a miniature-pig model of adolescent brain development for neuroimaging and neurophysiological assessment during this critical period. Minipigs have gyroencephalic brains with a large cerebral WM compartment and a well-defined adolescence period., Methods: Eight Sinclair™ minipigs (Sus scrofa domestica) were evaluated four times during weeks 14-28 (40, 28 and 28 days apart) of adolescence using monocular visual stimulation (1 Hz)-evoked potentials and diffusion MRI (dMRI) of WM. The latency for the pre-positive 30 ms (PP30), positive 30 ms (P30) and negative 50 ms (N50) components of the flash visual evoked potentials (fVEPs) and their interhemispheric latency (IL) were recorded in the frontal, central and occipital areas during ten 60-second stimulations for each eye. The dMRI imaging protocol consisted of fifteen b-shells (b = 0-3500 s/mm 2 ) with 32 directions/shell, providing measurements that included fractional anisotropy (FA), radial kurtosis, kurtosis anisotropy (KA), axonal water fraction (AWF), and the permeability-diffusivity index (PDI)., Results: Significant reductions (p < 0.05) in the latency and IL of fVEP measurements paralleled significant rises in FA, KA, AWF and PDI over the same period. The longitudinal latency changes in fVEPs were primarily associated with whole-brain changes in diffusion parameters, while fVEP IL changes were related to maturation of the corpus callosum., Conclusions: Good agreement between reduction in the latency of fVEPs and maturation of cerebral WM was interpreted as evidence for ongoing myelination and confirmation of the minipig as a viable research platform. Adolescent development in minipigs can be studied using human neuroimaging and neurophysiological protocols and followed up with more invasive assays to investigate key neurodevelopmental hypotheses in psychiatry., Competing Interests: Declaration of Competing Interest The authors have no conflicts of interest to declare. All co-authors have seen and agree with the contents of the manuscript and there is no financial interest to report., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Dopamine (DA) neurons of the substantia nigra (SN) and ventral tegmental area generally respond to aversive stimuli or the absence of expected rewards with transient inhibition of firing rates, which can be recapitulated with activation of the lateral habenula (LHb) and eliminated by lesioning the intermediating rostromedial tegmental nucleus (RMTg). However, a minority of DA neurons respond to aversive stimuli, such as foot shock, with a transient increase in firing rate, an outcome that rarely occurs with LHb stimulation. The degree to which individual neurons respond to these two stimulation modalities with the same response phenotype and the role of the RMTg is not known. Here, we record responses from single SN DA neurons to alternating activation of the LHb and foot shock in male rats. Lesions of the RMTg resulted in a shift away from inhibition to no response during both foot shock and LHb stimulation. Furthermore, lesions unmasked an excitatory response during LHb stimulation. The response correspondence within the same neuron between the two activation sources was no different from chance in sham controls, suggesting that external inputs rather than intrinsic DA neuronal properties are more important to response outcome. These findings contribute to a literature that shows a complex neurocircuitry underlies the regulation of DA activity and, by extension, behaviors related to learning, anhedonia, and cognition., (Copyright © 2024 IBRO. Published by Elsevier Inc. All rights reserved.)

Exposure to traumatic events during childhood increases the risk of adult psychopathology, including anxiety, depression, alcohol use disorders and their co-morbidity. Early life trauma also results in increased symptom complexity, treatment resistance and poor treatment outcomes. The purpose of this study was to establish a novel rodent model of adolescent stress, based on an ethologically relevant life-threatening event, live predator exposure. Rats were exposed to a live predator for 10 min. at three different time points (postnatal day (PND)31, 46 and 61). Adult depression-, anxiety-like behaviors and ethanol consumption were characterized well past the last acute stress event (two weeks). Behavioral profiles across assessments were developed to characterize individual response to adolescent stress. CNS activation patterns in separate groups of subjects were characterized after the early (PND31) and last predator exposure (PND61). Subjects exposed to live-predator adolescent stress generally exhibited less exploratory behavior, less propensity to venture into open spaces, a decreased preference for sweet solutions and decreased ethanol consumption in a two-bottle preference test. Additional studies demonstrated blunted cortisol response and CNS activation patterns suggestive of habenula, rostromedial tegmental (RMTg), dorsal raphe and central amygdala involvement in mediating the adult consequences of adolescent stress. Thus, adolescent stress in the form of live-predator exposure results in significant adult behavioral and neurobiological disturbances. Childhood trauma, its impact on neurodevelopment and the subsequent development of mood disorders is a pervasive theme in mental illness. Improving animal models and our neurobiological understanding of the symptom domains impacted by trauma could significantly improve treatment strategies., (Copyright © 2020. Published by Elsevier B.V.)

Cognitive-enhancing effects of nicotinic acetylcholine receptor (nAChR) agonists may be of therapeutic potential in disease states characterized by nAChR hypofunction; however, effects tend to be of small magnitude and unlikely clinical significance. The co-administration of a nAChR positive allosteric modulator (PAM) may enable larger effects by potentiating nAChR responses to an agonist. The acetylcholinesterase (AChE) inhibitor galantamine is a nAChR PAM at a low dose range. A recent clinical study testing effects of a single small dose of galantamine found evidence for synergistic effects with nicotine on one of several cognitive measures. In that study, residual AChE inhibition may have obscured interactions on other measures. The present study aimed at examining small galantamine doses devoid of AChE inhibitory activity in a rodent model of attention. The effects of galantamine (0.03-0.25 mg/kg s.c.) were tested in the presence and absence of nicotine (0.1 mg/kg s.c.) in rats performing the 5-Choice Serial Reaction Time Task, employing a within-subject factorial design. There were no effects on response accuracy of either nicotine or galantamine alone. However, the combination of nicotine and 0.06 mg/kg of galantamine significantly enhanced accuracy. AChE activity assays confirmed that, at this dose, galantamine was devoid of AChE inhibitory activity in the brain. The results suggest that cognitive-enhancing effects of nicotine may be potentiated or uncovered by an extremely small dose of galantamine, well below its typical therapeutic range in humans. Furthermore, these findings provide a general proof-of-principle for a nAChR agonist and PAM combination strategy for cognitive enhancement., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Early life trauma dramatically increases the risk of developing major depressive disorder (MDD), and is associated with a markedly decreased adult treatment response to antidepressants. Novel treatment approaches are required to treat childhood trauma-associated MDD. Recent studies suggest that the (R,S)-ketamine (ketamine) metabolite, (2R,6R)-hydroxynorketamine (HNK), exerts fast- and long-lasting antidepressant-like effects without ketamine's NMDAR-inhibition-associated adverse side-effect profile. We investigated the therapeutic potential of (2R,6R)-HNK against behavioral despair produced by a novel live-predator stress exposure during adolescence. Male and female C57BL/6J mice were exposed to a live snake or control conditions at post-natal (PND) days 31, 45 and 61. In order to assess the enduring consequences of trauma-exposure, at a minimum of 14 days following the last exposure, mice received inescapable shocks followed by a session with available escape options twenty-four hours later. Mice that manifested enduring escape deficits (helplessness) were treated with vehicle or (2R,6R)-HNK (20 mg/kg, i.p.), 24 h prior to retesting for reversal of escape deficits. We found that a significantly greater number of mice developed the helpless phenotype when they were exposed to the live predator and that the helpless phenotype was reversed in mice treated with (2R,6R)-HNK. There were no sex differences in the response to predator-stress exposure or (2R,6R)-HNK treatment. The live-predator model developed in this study provides an opportunity to further refine our understanding of the neurobiological substrates impacted by adolescent trauma and improve treatment strategies. The demonstrated efficacy of (2R,6R)-HNK in this model suggests a novel therapeutic intervention for a treatment-resistant population., (Copyright © 2020. Published by Elsevier Inc.)

Drug addiction is a chronic relapsing disorder of compulsive drug use. Studies of the neurobehavioral factors that promote drug relapse have yet to produce an effective treatment. Here we take a different approach and examine the factors that suppress-rather than promote-relapse. Adapting Pavlovian procedures to suppress operant drug response, we determined the anti-relapse action of environmental cues that signal drug omission (unavailability) in rats. Under laboratory conditions linked to compulsive drug use and heightened relapse risk, drug omission cues suppressed three major modes of relapse-promotion (drug-predictive cues, stress, and drug exposure) for cocaine and alcohol. This relapse-suppression is, in part, driven by omission cue-reactive neurons, which constitute small subsets of glutamatergic and GABAergic cells, in the infralimbic cortex. Future studies of such neural activity-based cellular units (neuronal ensembles/memory engram cells) for relapse-suppression can be used to identify alternate targets for addiction medicine through functional characterization of anti-relapse mechanisms.

A growing body of clinical and preclinical research suggests that structural and functional changes in the habenula, a component of the epithalamus, are associated with major depressive disorder. A major excitatory, efferent projection from the habenula targets the rostromedial tegmentum (RMTg), a mesopontine region that provides significant input to the ventral tegmentum and raphe nuclei. While the RMTg contributes to monoaminergic responses to aversive events, its role in stress-based animal models of depression has yet to be determined. In the present study, we test the hypothesis that the RMTg is a component of the circuitry mediating the development of a maladaptive behavior in which rats repeatedly exposed to inescapable footshock, fail to avoid or escape the same stressor when subsequently given the opportunity to do so. Excitotoxic lesions of the RMTg significantly diminished the frequency of these escape failures 24 h after exposure to inescapable footshock. Conversely, electrical stimulation of the Hb during the initial uncontrollable aversive event, a manipulation that enhances excitatory input to the RMTg, increased the number of trials in which subjects failed to escape an aversive stimulus when presented the option 24 h later. These complementary results provide evidence supporting a role for the RMTg in the expression of stress-induced helpless phenotype and are an important step in understanding the contribution made by this region to the development of depression-related maladaptive behaviors., (Copyright © 2018. Published by Elsevier B.V.)

A combination of genetic and environmental factors contributes to schizophrenia (SZ), a catastrophic psychiatric disorder with a hypothesized neurodevelopmental origin. Increases in the brain levels of the tryptophan metabolite kynurenic acid (KYNA), an endogenous antagonist of α7 nicotinic acetylcholine and NMDA receptors, have been implicated specifically in the cognitive deficits seen in persons with SZ. Here we evaluated this role of KYNA by adding the KYNA precursor kynurenine (100 mg/day) to chow fed to pregnant rat dams from embryonic day (ED) 15 to ED 22 (control: ECon; kynurenine treated: EKyn). Upon termination of the treatment, all rats received normal rodent chow until the animals were evaluated in adulthood (postnatal days 56-85). EKyn treatment resulted in increased extracellular KYNA and reduced extracellular glutamate in the hippocampus, measured by in vivo microdialysis, and caused impairments in hippocampus-dependent learning in adult rats. Acute administration of BFF816, a systemically active inhibitor of kynurenine aminotransferase II (KAT II), the major KYNA-synthesizing enzyme in the brain, normalized neurochemistry and prevented contextual memory deficits in adult EKyn animals. Collectively, these results demonstrate that acute inhibition of KYNA neosynthesis can overcome cognitive impairments that arise as a consequence of elevated brain KYNA in early brain development., (© 2018 Wiley Periodicals, Inc.)

Background: The volatile anesthetic isoflurane may exert a rapid and long-lasting antidepressant effect in patients with medication-resistant depression. The mechanism underlying the putative therapeutic actions of the anesthetic have been attributed to its ability to elicit cortical burst suppression, a distinct EEG pattern with features resembling the characteristic changes that occur following electroconvulsive therapy. It is currently unknown whether the antidepressant actions of isoflurane are shared by anesthetics that do not elicit cortical burst suppression., Methods: In vivo electrophysiological techniques were used to determine the effects of isoflurane and halothane, 2 structurally unrelated volatile anesthetics, on cortical EEG. The effects of anesthesia with either halothane or isoflurane were also compared on stress-induced learned helplessness behavior in rats and mice., Results: Isoflurane, but not halothane, anesthesia elicited a dose-dependent cortical burst suppression EEG in rats and mice. Two hours of isoflurane, but not halothane, anesthesia reduced the incidence of learned helplessness in rats evaluated 2 weeks following exposure. In mice exhibiting a learned helplessness phenotype, a 1-hour exposure to isoflurane, but not halothane, reversed escape failures 24 hours following burst suppression anesthesia., Conclusions: These results are consistent with a role for cortical burst suppression in mediating the antidepressant effects of isoflurane. They provide rationale for additional mechanistic studies in relevant animal models as well as a properly controlled clinical evaluation of the therapeutic benefits associated with isoflurane anesthesia in major depressive disorder., (© The Author(s) 2018. Published by Oxford University Press on behalf of CINP.)

Neurons in the lateral habenula (LHb) are transiently activated by aversive events and have been implicated in associative learning. Functional changes associated with tonic and phasic activation of the LHb are often attributed to a corresponding inhibition of midbrain dopamine (DA) neurons. Activation of GABAergic neurons in the rostromedial tegmental nucleus (RMTg), a region that receives dense projections from the LHb and projects strongly to midbrain monoaminergic nuclei, is believed to underlie the transient inhibition of DA neurons attributed to activation of the LHb. To test this premise, the effects of axon-sparing lesions of the RMTg were assessed on LHb-induced inhibition of midbrain DA cell firing in anesthetized rats. Quinolinic acid lesions decreased the number of NeuN-positive neurons in the RMTg significantly while largely sparing cells in neighboring regions. Lesions of the RMTg reduced both the number of DA neurons inhibited by, and the duration of inhibition resulting from, LHb stimulation. Although the firing rate was not altered, the regularity of DA cell firing was increased in RMTg-lesioned rats. Locomotor activity in an open field was also elevated. These results are the first to show that RMTg neurons contribute directly to LHb-induced inhibition of DA cell activity and support the widely held proposition that GABAergic neurons in the mesopontine tegmentum are an important component of a pathway that enables midbrain DA neurons to encode the negative valence associated with failed expectations and aversive stimuli., Significance Statement: Phasic changes in the activity of midbrain dopamine cells motivate and guide future behavior. Activation of the lateral habenula by aversive events inhibits dopamine neurons transiently, providing a neurobiological representation of learning models that incorporate negative reward prediction errors. Anatomical evidence suggests that this inhibition occurs via the rostromedial tegmental nucleus, but this hypothesis has yet to be tested directly. Here, we show that axon-sparing lesions of the rostromedial tegmentum attenuate habenula-induced inhibition of dopamine neurons significantly. These data support a substantial role for the rostromedial tegmentum in habenula-induced feedforward inhibition of dopamine neurons., (Copyright © 2017 the authors 0270-6474/17/370217-09$15.00/0.)

The Research Domain Criteria (RDoC) initiative was implemented to reorient the approach to mental health research from one focused on Diagnostic and Statistical Manual of Mental Disorders (DSM) nosology to one oriented to psychological constructs constrained by neurocircuitry and molecular entities. The initiative has generated significant discussion and valuable reflection on the moorings of psychiatric research. The purpose of this article is to illustrate how a basic or clinical investigator can engage RDoC to explore the neurobiological underpinnings of psychopathology and how a research question can be formulated in RDoC's framework. We utilize a brain region with significant growing interest, the habenula, as an example for probing RDoC's utility. Opportunities to enhance neurocircuitry-psychological construct associations and problems associated with neuronal populations that enable bidirectional circuitry influence are discussed. The exercise reveals areas for further development that could move RDoC from a promising research idea to a successfully engaged foundation for catalyzing clinically relevant discoveries., (© The Author 2016. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Major depressive disorder affects around 16 per cent of the world population at some point in their lives. Despite the availability of numerous monoaminergic-based antidepressants, most patients require several weeks, if not months, to respond to these treatments, and many patients never attain sustained remission of their symptoms. The non-competitive, glutamatergic NMDAR (N-methyl-d-aspartate receptor) antagonist (R,S)-ketamine exerts rapid and sustained antidepressant effects after a single dose in patients with depression, but its use is associated with undesirable side effects. Here we show that the metabolism of (R,S)-ketamine to (2S,6S;2R,6R)-hydroxynorketamine (HNK) is essential for its antidepressant effects, and that the (2R,6R)-HNK enantiomer exerts behavioural, electroencephalographic, electrophysiological and cellular antidepressant-related actions in mice. These antidepressant actions are independent of NMDAR inhibition but involve early and sustained activation of AMPARs (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors). We also establish that (2R,6R)-HNK lacks ketamine-related side effects. Our data implicate a novel mechanism underlying the antidepressant properties of (R,S)-ketamine and have relevance for the development of next-generation, rapid-acting antidepressants.

Rationale: Processes of attention have a heritable component, suggesting that genetic predispositions may predict variability in the response to attention-enhancing drugs. Among lead compounds with attention-enhancing properties are nicotinic acetylcholine receptor (nAChR) agonists., Objectives: This study aims to test, by comparing three rat strains, whether genotype may influence the sensitivity to nicotine in the 5-choice serial reaction time task (5-CSRTT), a rodent model of attention., Methods: Strains tested were Long Evans (LE), Sprague Dawley (SD), and Wistar rats. The 5-CSRTT requires responses to light stimuli presented randomly in one of five locations. The effect of interest was an increased percentage of responses in the correct location (accuracy), the strongest indicator of improved attention., Results: Nicotine (0.05-0.2 mg/kg s.c.) reduced omission errors and response latency and increased anticipatory responding in all strains. In contrast, nicotine dose-dependently increased accuracy in Wistar rats only. The nAChR antagonist mecamylamine (0.75-3 mg/kg s.c.) increased omissions, slowed responses, and reduced anticipatory responding in all strains. There were no effects on accuracy, which was surprising giving the clear improvement with nicotine in the Wistar group., Conclusions: The findings suggest strain differences in the attention-enhancing effects of nicotine, which would indicate that genetic predispositions predict variability in the efficacy of nAChR compounds for enhancing attention. The absence of effect of mecamylamine on response accuracy may suggest a contribution of nAChR desensitization to the attention-enhancing effects of nicotine.

Long-term opioid treatment results in reduced therapeutic efficacy and in turn leads to an increase in the dose required to produce equivalent pain relief and alleviate break-through or insurmountable pain. Altered gene expression is a likely means for inducing long-term neuroadaptations responsible for tolerance. Studies conducted by our laboratory (Tapocik et al., 2009) revealed a network of gene expression changes occurring in canonical pathways involved in neuroplasticity, and uncovered miRNA processing as a potential mechanism. In particular, the mRNA coding the protein responsible for processing miRNAs, Dicer1, was positively correlated with the development of analgesic tolerance. The purpose of the present study was to test the hypothesis that miRNAs play a significant role in the development of analgesic tolerance as measured by thermal nociception. Dicer1 knockdown, miRNA profiling, bioinformatics, and confirmation of high value targets were used to test the proposition. Regionally targeted Dicer1 knockdown (via shRNA) had the anticipated consequence of eliminating the development of tolerance in C57BL/6J (B6) mice, thus supporting the involvement of miRNAs in the development of tolerance. MiRNA expression profiling identified a core set of chronic morphine-regulated miRNAs (miR's 27a, 9, 483, 505, 146b, 202). Bioinformatics approaches were implemented to identify and prioritize their predicted target mRNAs. We focused our attention on miR27a and its predicted target serpin peptidase inhibitor clade I (Serpini1) mRNA, a transcript known to be intricately involved in dendritic spine density regulation in a manner consistent with chronic morphine's consequences and previously found to be correlated with the development of analgesic tolerance. In vitro reporter assay confirmed the targeting of the Serpini1 3'-untranslated region by miR27a. Interestingly miR27a was found to positively regulate Serpini1 mRNA and protein levels in multiple neuronal cell lines. Lastly, Serpini1 knockout mice developed analgesic tolerance at a slower rate than wild-type mice thus confirming a role for the protein in analgesic tolerance. Overall, these results provide evidence to support a specific role for miR27a and Serpini1 in the behavioral response to chronic opioid administration (COA) and suggest that miRNA expression and mRNA targeting may underlie the neuroadaptations that mediate tolerance to the analgesic effects of morphine.

Rationale: Cognitive dysfunctions, including deficits in hippocampus-mediated learning and memory, are core features of the psychopathology of schizophrenia (SZ). Increased levels of kynurenic acid (KYNA), an astrocyte-derived tryptophan metabolite and antagonist of α7 nicotinic acetylcholine and N-methyl-D-aspartate receptors, have been implicated in these cognitive impairments., Objectives: Following recent suggestive evidence, the present study was designed to narrow the critical time period for KYNA elevation to induce subsequent cognitive deficits., Methods: KYNA levels were experimentally increased in rats (1) prenatally (embryonic day (ED) 15 to ED 22) or (2) during adolescence (postnatal day (PD) 42 to PD 49). The KYNA precursor kynurenine was added daily to wet mash fed to (1) dams (100 mg/day; control: ECon; kynurenine-treated: EKyn) or (2) adolescent rats (300 mg/kg/day; control: AdCon; kynurenine-treated: AdKyn). Upon termination of the treatment, all animals were fed normal chow until biochemical analysis and behavioral testing in adulthood., Results: On the last day of continuous kynurenine treatment, forebrain KYNA levels were significantly elevated (EKyn +472 %; AdKyn +470 %). KYNA levels remained increased in the hippocampus of adult EKyn animals (+54 %), but were unchanged in adult AdKyn rats. Prenatal, but not adolescent, kynurenine treatment caused significant impairments in two hippocampus-mediated behavioral tasks, passive avoidance and Morris water maze., Conclusions: Collectively, these studies provide evidence that a continuous increase in brain KYNA levels during the late prenatal period, but not during adolescence, induces hippocampus-related cognitive dysfunctions later in life. Such increases may play a significant role in illnesses with known hippocampal pathophysiology, including SZ.

Rationale: In psychiatric drug discovery, a critical step is predicting the psychopharmacological effect and therapeutic potential of novel (or repurposed) compounds early in the development process. This process is hampered by the need to utilize multiple disorder-specific and labor-intensive behavioral assays., Objectives: This study aims to investigate the feasibility of a single high-throughput behavioral assay to classify psychiatric drugs into multiple psychopharmacological classes., Methods: Using Pattern Array, a procedure for data mining exploratory behavior in mice, we mined ~100,000 complex movement patterns for those that best predict psychopharmacological class and dose. The best patterns were integrated into a classification model that assigns psychopharmacological compounds to one of six clinically relevant classes--antipsychotic, antidepressant, opioids, psychotomimetic, psychomotor stimulant, and α-adrenergic., Results: Surprisingly, only a small number of well-chosen behaviors were required for successful class prediction. One of them, a behavior termed "universal drug detector", was dose-dependently decreased by drugs from all classes, thus providing a sensitive index of psychopharmacological activity. In independent validation in a blind fashion, simulating the process of in vivo pre-clinical drug screening, the classification model correctly classified nine out of 11 "unknown" compounds. Interestingly, even "misclassifications" match known alternate therapeutic indications, illustrating drug "repurposing" potential., Conclusions: Unlike standard animal models, the discovered classification model can be systematically updated to improve its predictive power and add therapeutic classes and subclasses with each additional diversification of the database. Our study demonstrates the power of data mining approaches for behavior analysis, using multiple measures in parallel for drug screening and behavioral phenotyping.

The attribution of incentive salience to reward associated cues is critical for motivation and the pursuit of rewards. Disruptions in the integrity of the neural systems controlling these processes can lead to avolition and anhedonia, symptoms that cross the diagnostic boundaries of many neuropsychiatric illnesses. Here, we consider whether the habenula (Hb), a region recently demonstrated to encode negatively valenced events, also modulates the attribution of incentive salience to a neutral cue predicting a food reward. The Pavlovian autoshaping paradigm was used in the rat as an investigative tool to dissociate Pavlovian learning processes imparting strictly predictive value from learning that attributes incentive motivational value. Electrolytic lesions of the fasciculus retroflexus (fr), the sole pathway through which descending Hb efferents are conveyed, significantly increased incentive salience as measured by conditioned approaches to a cue light predictive of reward. Conversely, generation of a fictive Hb signal via fr stimulation during CS+ presentation significantly decreased the incentive salience of the predictive cue. Neither manipulation altered the reward predictive value of the cue as measured by conditioned approach to the food. Our results provide new evidence supporting a significant role for the Hb in governing the attribution of incentive motivational salience to reward predictive cues and further imply that pathological changes in Hb activity could contribute to the aberrant pursuit of debilitating goals or avolition and depression-like symptoms.

While glutamate in the nucleus accumbens (NAS) contributes to the promotion of drug-seeking by drug-predictive cues, it also appears to play a role in the inhibition of drug-seeking following extinction procedures. Thus we measured extracellular fluctuations of NAS glutamate in response to discriminative stimuli that signaled either cocaine availability or cocaine omission. We trained rats to self-administer intravenous cocaine and then to recognize discriminative odor cues that predicted either sessions where cocaine was available or alternating sessions where it was not (saline substituted for cocaine). Whereas responding in cocaine availability sessions remained stable, responding in cocaine omission sessions progressively declined to chance levels. We then determined the effects of each odor cue on extracellular glutamate in the core and shell subregions of NAS preceding and accompanying lever pressing under an extinction condition. Glutamate levels were elevated in both core and shell by the availability odor and depressed in the core but not the shell by the omission odor. Infusion of kynurenic acid (an antagonist for ionotropic glutamate receptors) into core but not shell suppressed responding associated with the availability odor, but had no effect on the suppression associated with the omission odor. Thus cocaine-predictive cues appear to promote cocaine seeking in part by elevating glutamatergic neurotransmission in the core of NAS, whereas cocaine-omission cues appear to suppress cocaine seeking in part by depressing glutamatergic receptor activation in the same region.

Neuroadaptations in the ventral striatum (VS) and ventral midbrain (VMB) following chronic opioid administration are thought to contribute to the pathogenesis and persistence of opiate addiction. In order to identify candidate genes involved in these neuroadaptations, we utilized a behavior-genetics strategy designed to associate contingent intravenous drug self-administration with specific patterns of gene expression in inbred mice differentially predisposed to the rewarding effects of morphine. In a Yoked-control paradigm, C57BL/6J mice showed clear morphine-reinforced behavior, whereas DBA/2J mice did not. Moreover, the Yoked-control paradigm revealed the powerful consequences of self-administration versus passive administration at the level of gene expression. Morphine self-administration in the C57BL/6J mice uniquely up- or down-regulated 237 genes in the VS and 131 genes in the VMB. Interestingly, only a handful of the C57BL/6J self-administration genes (<3%) exhibited a similar expression pattern in the DBA/2J mice. Hence, specific sets of genes could be confidently assigned to regional effects of morphine in a contingent- and genotype-dependent manner. Bioinformatics analysis revealed that neuroplasticity, axonal guidance and micro-RNAs (miRNAs) were among the key themes associated with drug self-administration. Noteworthy were the primary miRNA genes H19 and micro-RNA containing gene (Mirg), processed, respectively, to mature miRNAs miR-675 and miR-154, because they are prime candidates to mediate network-like changes in responses to chronic drug administration. These miRNAs have postulated roles in dopaminergic neuron differentiation and mu-opioid receptor regulation. The strategic approach designed to focus on reinforcement-associated genes provides new insight into the role of neuroplasticity pathways and miRNAs in drug addiction., (© 2012 The Authors, Addiction Biology © 2012 Society for the Study of Addiction.)

Adult rats exposed to the DNA-methylating agent methylazoxymethanol on embryonic day 17 show a pattern of neurobiological deficits that model some of the neuropathological and behavioral changes observed in schizophrenia. Although it is generally assumed that these changes reflect targeted disruption of embryonic neurogenesis, it is unknown whether these effects generalise to other antimitotic agents administered at different stages of development. In the present study, neurochemical, behavioral and electrophysiological techniques were used to determine whether exposure to the antimitotic agent Ara-C later in development recapitulates some of the changes observed in methylazoxymethanol (MAM)-treated animals and in patients with schizophrenia. Male rats exposed to Ara-C (30 mg/kg/day) at embryonic days 19.5 and 20.5 show reduced cell numbers and heterotopias in hippocampal CA1 and CA2/3 regions, respectively, as well as cell loss in the superficial layers of the pre- and infralimbic cortex. Birth date labeling with bromodeoxyuridine reveals that the cytoarchitectural changes in CA2/3 are a consequence rather that a direct result of disrupted cortical neurogenesis. Ara-C-treated rats possess elevated levels of cortical dopamine and DOPAC (3,4-didyhydroxypheylacetic acid) but no change in norepinephrine or serotonin. Ara-C-treated rats are impaired in their ability to learn the Morris water maze task and showed diminished synaptic plasticity in the hippocampocortical pathway. These data indicate that disruption of neurogenesis at embryonic days 19.5 and 20.5 constitutes a useful model for the comparative study of deficits observed in other gestational models and their relationship to cognitive changes observed in schizophrenia., (© 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.)

Levels of kynurenic acid (KYNA), an endogenous product of tryptophan degradation, are elevated in the brain and cerebrospinal fluid of individuals with schizophrenia (SZ). This increase has been implicated in the cognitive dysfunctions seen in the disease, as KYNA is an antagonist of the α7 nicotinic acetylcholine receptor and the N-methyl-d-aspartate receptor, both of which are critically involved in cognitive processes and in a defining neurodevelopmental period in the pathophysiology of SZ. We tested the hypothesis that early developmental increases in brain KYNA synthesis might cause biochemical and functional impairments in adulthood. To this end, we stimulated KYNA formation by adding the KYNA precursor kynurenine (100 mg/day) to the chow fed to rat dams from gestational day 15 to postnatal day 21 (PD 21). This treatment raised brain KYNA levels in the offspring by 341% on PD 2 and 210% on PD 21. Rats were then fed normal chow until adulthood (PD 56-80). In the adult animals, basal levels of extracellular KYNA, measured in the hippocampus by in vivo microdialysis, were elevated (+12%), whereas extracellular glutamate levels were significantly reduced (-13%). In separate adult animals, early kynurenine treatment was shown to impair performance in two behavioral tasks linked to hippocampal function, the passive avoidance test and the Morris water maze test. Collectively, these studies introduce a novel, naturalistic rat model of SZ, and also suggest that increases in brain KYNA during a vulnerable period in brain development may play a significant role in the pathophysiology of the disease., (© 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.)

The rewarding properties of psychomotor stimulants are traditionally thought to be independent of norepinephrine. Recent findings, however, suggest that local noradrenergic signaling through α1 receptors in the medial prefrontal cortex and the ventral tegmental area - brain regions critically important in natural and drug rewards - is in a position to influence stimulant reward. Despite this controversy, the contribution of this targeted signaling to stimulant self-administration has not been directly assessed. We have thus examined whether pharmacological blockade of α1 receptors in the medial prefrontal cortex and ventral tegmental area alters cocaine self-administration. Rats were trained to lever-press for cocaine (1.0 mg/kg/infusion) under a fixed ratio 1 schedule of reinforcement for 10 days. After training, the rats received a bilateral microinjection of an α1 noradrenergic antagonist (terazosin: 1.0, 5.0, or 10 mM/side), a D1 dopaminergic antagonist (SCH23390: 12.3 mM/side), or saline into either the medial prefrontal cortex or ventral tegmental area immediately before a cocaine self-administration session. Although SCH23390 significantly increased cocaine self-administration when injected into either brain region, terazosin, at all doses and sites tested, failed to alter this behavior. Thus, the maintenance of cocaine self-administration appears to be under the influence of D1 dopaminergic, rather than α1 noradrenergic, signaling at these mesocortical sites.

Kynurenic acid (KYNA), an astrocyte-derived metabolite, antagonizes the α7 nicotinic acetylcholine receptor (α7nAChR) and, possibly, the glycine co-agonist site of the NMDA receptor at endogenous brain concentrations. As both receptors are involved in cognitive processes, KYNA elevations may aggravate, whereas reductions may improve, cognitive functions. We tested this hypothesis in rats by examining the effects of acute up- or downregulation of endogenous KYNA on extracellular glutamate in the hippocampus and on performance in the Morris water maze (MWM). Applied directly by reverse dialysis, KYNA (30-300 nM) reduced, whereas the specific kynurenine aminotransferase-II inhibitor (S)-4-(ethylsulfonyl)benzoylalanine (ESBA; 0.3-3 mM) raised, extracellular glutamate levels in the hippocampus. Co-application of KYNA (100 nM) with ESBA (1 mM) prevented the ESBA-induced glutamate increase. Comparable effects on hippocampal glutamate levels were seen after intra-cerebroventricular (i.c.v.) application of the KYNA precursor kynurenine (1 mM, 10 μl) or ESBA (10 mM, 10 μl), respectively. In separate animals, i.c.v. treatment with kynurenine impaired, whereas i.c.v. ESBA improved, performance in the MWM. I.c.v. co-application of KYNA (10 μM) eliminated the pro-cognitive effects of ESBA. Collectively, these studies show that KYNA serves as an endogenous modulator of extracellular glutamate in the hippocampus and regulates hippocampus-related cognitive function. Our results suggest that pharmacological interventions leading to acute reductions in hippocampal KYNA constitute an effective strategy for cognitive improvement. This approach might be especially useful in the treatment of cognitive deficits in neurological and psychiatric diseases that are associated with increased brain KYNA levels.

At endogenous brain concentrations, the astrocyte-derived metabolite kynurenic acid (KYNA) antagonizes the alpha 7 nicotinic acetylcholine receptor and, possibly, the glycine co-agonist site of the NMDA receptor. The functions of these two receptors, which are intimately involved in synaptic plasticity and cognitive processes, may, therefore, be enhanced by reductions in brain KYNA levels. This concept was tested in mice with a targeted deletion of kynurenine aminotransferase II (KAT II), a major biosynthetic enzyme of brain KYNA. At 21 days of age, KAT II knock-out mice had reduced hippocampal KYNA levels (-71%) and showed significantly increased performance in three cognitive paradigms that rely in part on the integrity of hippocampal function, namely object exploration and recognition, passive avoidance, and spatial discrimination. Moreover, compared with wild-type controls, hippocampal slices from KAT II-deficient mice showed a significant increase in the amplitude of long-term potentiation in vitro. These functional changes were accompanied by reduced extracellular KYNA (-66%) and increased extracellular glutamate (+51%) concentrations, measured by hippocampal microdialysis in vivo. Taken together, a picture emerges in which a reduction in the astrocytic formation of KYNA increases glutamatergic tone in the hippocampus and enhances cognitive abilities and synaptic plasticity. Our studies raise the prospect that interventions aimed specifically at reducing KYNA formation in the brain may constitute a promising molecular strategy for cognitive improvement in health and disease.

Antipsychotic drugs are broadly classified into typical and atypical compounds; they vary in their pharmacological profile however a common component is their antagonist effects at the D2 dopamine receptors (DRD2). Unfortunately, diminished DRD2 activation is generally thought to be associated with the severity of neuroleptic-induced anhedonia. The purpose of this study was to determine the effect of the atypical antipsychotic olanzapine and typical antipsychotic haloperidol in a paradigm that reflects the learned transfer of incentive motivational properties to previously neutral stimuli, namely autoshaping. In order to provide a dosing comparison to a therapeutically relevant endpoint, both drugs were tested against amphetamine-induced disruption of prepulse inhibition as well. In the autoshaping task, rats were exposed to repeated pairings of stimuli that were differentially predictive of reward delivery. Conditioned approach to the reward-predictive cue (sign-tracking) and to the reward (goal-tracking) increased during repeated pairings in the vehicle treated rats. Haloperidol and olanzapine completely abolished this behavior at relatively low doses (100microg/kg). This same dose was the threshold dose for each drug to antagonize the sensorimotor gating deficits produced by amphetamine. At lower doses (3-30microg/kg) both drugs produced a dose-dependent decrease in conditioned approach to the reward-predictive cue. There was no difference between drugs at this dose range which indicates that olanzapine disrupts autoshaping at a significantly lower proposed DRD2 receptor occupancy. Interestingly, neither drug disrupted conditioned approach to the reward at the same dose range that disrupted conditioned approach to the reward-predictive cue. Thus, haloperidol and olanzapine, at doses well below what is considered therapeutically relevant, disrupts the attribution of incentive motivational value to previously neutral cues. Drug effects on this dimension of reward processing are an important consideration in the development of future pharmacological treatments for schizophrenia., (Copyright 2010 Elsevier Inc. All rights reserved.)

In this study we tested the hypothesis that long-term neuropathological outcome is worsened by hyperoxic compared to normoxic reperfusion in a rat global cerebral ischemia model. Adult male rats were anesthetized and subjected to bilateral carotid arterial occlusion plus bleeding hypotension for 10 min. The rats were randomized to one of four protocols: ischemia/normoxia (21% oxygen for 1 h), ischemia/hyperoxia (100% oxygen for 1 h), sham/normoxia, and sham/hyperoxia. Hippocampal CA1 neuronal survival and activation of microglia and astrocytes were measured in the hippocampi of the animals at 7 and 30 days post-ischemia. Morris water maze testing of memory was performed on days 23-30. Compared to normoxic reperfusion, hyperoxic ventilation resulted in a significant decrease in normal-appearing neurons at 7 and 30 days, and increased activation of microglia and astrocytes at 7, but not at 30, days of reperfusion. Behavioral deficits were also observed following hyperoxic, but not normoxic, reperfusion. We conclude that early post-ischemic hyperoxic reperfusion is followed by greater hippocampal neuronal death and cellular inflammatory reactions compared to normoxic reperfusion. The results of these long-term outcome studies, taken together with previously published results from short-term experiments performed with large animals, support the hypothesis that neurological outcome can be improved by avoiding hyperoxic resuscitation after global cerebral ischemia such as that which accompanies cardiac arrest.

Rationale: The C57BL/6J (C57) and DBA/2J (DBA) mice are the most common genotypes used to identify chromosomal regions and neurochemical mechanisms of interest in opioid addiction. Unfortunately, outside of the oral two-bottle choice procedure, limited and sometimes controversial evidence is available for determining their relative sensitivity to the rewarding effects of morphine., Objectives: The purpose of this study was to utilize classically accepted models of drug abuse liability to determine relative susceptibility to the rewarding effects of morphine., Methods: The ability of morphine or amphetamine to potentiate lateral hypothalamic brain stimulation and intravenous morphine self-administration (across three doses in a fixed ratio schedule and at the highest dose in progressive ratio schedules) was investigated in both genotypes., Results: In both measures, C57 and DBA mice differed dramatically in their response to morphine. Morphine potentiated rewarding stimulation in the C57 mice but antagonized it in the DBA mice. Consistent with these findings, intravenous morphine did not serve as a positive reinforcer in DBA mice under conditions that were effective in the C57 mice using a fixed ratio schedule and failed to sustain levels of responding sufficient to maintain a constant rate of drug intake under a progressive ratio schedule. In contrast, amphetamine potentiated the rewarding effects of brain stimulation similarly in the two genotypes., Conclusions: These findings provide strong evidence that morphine is rewarding in the C57 genotype and not in the DBA genotype. Understanding their relative susceptibility is important given the prominence of these genotypes in candidate gene identification and gene mapping.

Rationale: Deficits in memory and attention are broadly acknowledged during psychosis; however, experiments on modeled psychosis often test working memory without systematic manipulation of attentional demands., Objectives: The major research goal was discovering which neurobehavioral processes, attention, or memory contributed more to drug-provoked performance deficits., Materials and Methods: Rats were trained to perform operant ratio discrimination (RD) tasks wherein the number of presses at a rear-wall lever was discriminated using one of two front-wall levers. Effects from four psychotomimetic drugs, the serotonin agonist 2,5-dimethoxy-4-iodoamphetamine, the noncompetitive NMDA-glutamate receptor antagonist phencyclidine (PCP), and two CB1-selective cannabinoid agonists, WIN 55,512-2 and AM 411, were assessed using a signal detection analytical overlay to dissociate cognitive from noncognitive motor and motivational disruptions. Further methods allowed dissociation of attention compromises from mnemonic deficits., Results: For each test compound, at least one dose elicited decreased RD accuracy without affecting response rates, and task difficulty was shown to be a crucial dictator of accuracy effect specificities. Effects from both PCP and WIN 55,512-2 biased animals to select the response lever conditioned for denser reinforcement. The same two drugs rendered peculiar response patterns in distracter light session components, considering light blinks were included to divert subjects' attention away from task-relevant information. The response patterns determined during distracter components of PCP/WIN testing sessions, counterintuitively, suggest performance enhancement., Conclusion: Comprehensive viewing of RD performance patterns after drug administration indicates that sustained attention and transient information management are significantly impaired during the drug-induced psychosis state, while selective attention is less affected.

Chronic morphine administration may alter the expression of hundreds to thousands of genes. However, only a subset of these genes is likely involved in analgesic tolerance. In this report, we used a behavior genetics strategy to identify candidate genes specifically linked to the development of morphine tolerance. Two inbred genotypes [C57BL/6J (B6), DBA2/J (D2)] and two reciprocal congenic genotypes (B6D2, D2B6) with the proximal region of chromosome 10 (Chr10) introgressed into opposing backgrounds served as the behavior genetic filter. Tolerance after therapeutically relevant doses of morphine developed most rapidly in the B6 followed by the B6D2 genotype and did not develop in the D2 mice and only slightly in the D2B6 animals indicating a strong influence of the proximal region of Chr10 in the development of tolerance. Gene expression profiling and pattern matching identified 64, 53, 86, and 123 predisposition genes and 81, 96, 106, and 82 tolerance genes in the periaqueductal gray (PAG), prefrontal cortex, temporal lobe, and ventral striatum, respectively. A potential gene network was identified in the PAG in which 19 of the 34 genes were strongly associated with tolerance. Eleven of the network genes were found to reside in quantitative trait loci previously associated with morphine-related behaviors, whereas seven were predictive of tolerance (morphine-naive condition). Overall, the genes modified by chronic morphine administration show a strong presence in canonical pathways representative of neuroadaptation. A potentially significant role for the micro-RNA and epigenetic mechanisms in response to chronic administration of pharmacologically relevant doses of morphine was highlighted by candidate genes Dicer and H19.

Social recognition reflects the ability of one animal to learn and remember the identity of another. Animal models of social learning and memory are pertinent to several different CNS diseases involving disruptions in cognition. Moreover, the increased understanding of the basic biology of memory increases the likelihood of discovery of memory-enhancing treatments in these human diseases. In the present study, we investigated the effects of the non-competitive NMDA antagonist ketamine on social recognition in mice across a broad dose range (5-30 mg/kg) and time-course (60 min-7 days). We also tested the ability of two antipsychotic drugs, haloperidol and olanzapine, to block the ketamine effect. Our results show that mice demonstrate social recognition over a several day period, with loss of recognition between 3-7 days. Ketamine disrupts social memory at doses which do not affect task performance. Chronic oral administration of haloperidol or olanzapine attenuates these ketamine-induced effects on social recognition, tending to normalize the memory behavior. The neural mechanisms of these actions are not known, although medial temporal lobe memory systems have been implicated.

The discovery of truly efficacious treatments that lead to full recovery is a daunting task in psychiatric illness. A systems-based orientation to in vivo pharmacology has been suggested as a way to transform psychiatric drug discovery and development. A critical catalyst in the success of recent systems biology efforts has been the incorporation of data mining strategies. Our approach to the drug discovery problem has been to utilize the whole animal to provide a systems response that is subsequently mined for predictive attributes with known psychopharmacological value. Our in vivo data mining approach, termed Pattern Array, establishes a framework for screening novel chemical entities based upon a response that represents the net pharmacological effect on the system of interest, namely the central nervous system (CNS). Large scale screening of small molecules by non-conventional approaches such as this at a systems level may improve the identification of novel chemical entities with psychiatric utility. This type of approach will compliment the more labor-intensive models based upon construct validity. It will take the collective effort of many disciplines and numerous strategies in close association with clinical colleagues to address quality of life issues and breakthrough treatment barriers in psychiatric illness.

Data mining is a powerful bioinformatics strategy that has been successfully applied in vitro to screen for gene-expression profiles predicting toxicological or carcinogenic response ('class predictors'). In this report we used a data mining algorithm named Pattern Array (PA) in vivo to analyze mouse open-field behavior and characterize the psychopharmacological effects of three drug classes--psychomotor stimulant, opioid, and psychotomimetic. PA represents rodent movement with approximately 100,000 complex patterns, defined as multiple combinations of several ethologically relevant variables, and mines them for those that maximize any effect of interest, such as the difference between drug classes. We show that PA can discover behavioral predictors of all three drug classes, thus developing a reliable drug-classification scheme in small group sizes. The discovered predictors showed orderly dose dependency despite being explicitly mined only for class differences, with the high doses scoring 4-10 standard deviations from the vehicle group. Furthermore, these predictors correctly classified in a dose-dependent manner four 'unknown' drugs (ie that were not used in the training process), and scored a mixture of a psychomotor stimulant and an opioid as being intermediate between these two classes. The isolated behaviors were highly heritable (h(2)>50%) and replicable as determined in 10 inbred strains across three laboratories. PA can in principle be applied for mining behaviors predicting additional properties, such as within-class differences between drugs and within-drug dose-response, all of which can be measured automatically in a single session per animal in an open-field arena, suggesting a high potential as a tool in psychotherapeutic drug discovery.

"What's wrong with my genetically engineered animal?" is a common yet often difficult to answer question in behavioral phenotyping. We present here a method termed Pattern Array for mining movement patterns and isolating those that best capture an effect of a genetic manipulation. We demonstrate the method by searching for early motor symptoms in the open-field behavior of SOD1 mutant rats, an animal model of amyotrophic lateral sclerosis. Pattern Array was able to identify a unique motor pattern that differentiated the SOD1 mutants from the wild-type controls 2 months before disease onset. This pattern included heavy braking while moving near the arena wall but turning away from it. SOD1 mutants performed this pattern significantly less than wild-type controls in 2 independent data sets. At such early age the SOD1 mutants could not be differentiated from the controls by standard behavioral measures or by subjective observation. The early discovered symptom may enable investigators to test therapies aimed for intervention rather than remediation. Our results demonstrate the feasibility and potential of detecting subtle behavioral effects using data mining strategies.

Unlabelled: Gene expression and phenotypic functionality can best be associated when they are measured quantitatively within the same experiment. The analysis of such a complex experiment is presented, searching for associations between measures of exploratory behavior in mice and gene expression in brain regions. The analysis of such experiments raises several methodological problems. First and foremost, the size of the pool of potential discoveries being screened is enormous yet only few biologically relevant findings are expected, making the problem of multiple testing especially severe. We present solutions based on screening by testing related hypotheses, then testing the hypotheses of interest. In one variant the subset is selected directly, in the other one a tree of hypotheses is tested hierarchical; both variants control the False Discovery Rate (FDR). Other problems in such experiments are in the fact that the level of data aggregation may be different for the quantitative traits (one per animal) and gene expression measurements (pooled across animals); in that the association may not be linear; and in the resolution of interest only few replications exist. We offer solutions to these problems as well. The hierarchical FDR testing strategies presented here can serve beyond the structure of our motivating example study to any complex microarray study., Supplementary Information: Supplementary data are available at Bioinformatics online.

In this report we link candidate genes to complex behavioral phenotypes by using a behavior genetics approach. Gene expression signatures were generated for the prefrontal cortex, ventral striatum, temporal lobe, periaqueductal gray, and cerebellum in eight inbred strains from priority group A of the Mouse Phenome Project. Bioinformatic analysis of regionally enriched genes that were conserved across all strains revealed both functional and structural specialization of particular brain regions. For example, genes encoding proteins with demonstrated anti-apoptotic function were over-represented in the cerebellum, whereas genes coding for proteins associated with learning and memory were enriched in the ventral striatum, as defined by the Expression Analysis Systematic Explorer (EASE) application. Association of regional gene expression with behavioral phenotypes was exploited to identify candidate behavioral genes. Phenotypes that were investigated included anxiety, drug-naive and ethanol-induced distance traveled across a grid floor, and seizure susceptibility. Several genes within the glutamatergic signaling pathway (i.e., NMDA/glutamate receptor subunit 2C, calmodulin, solute carrier family 1 member 2, and glutamine synthetase) were identified in a phenotype-dependent and region-specific manner. In addition to supporting evidence in the literature, many of the genes that were identified could be mapped in silico to surrogate behavior-related quantitative trait loci. The approaches and data set described herein serve as a valuable resource to investigate the genetic underpinning of complex behaviors.

Rationale: The rewarding effects of lateral hypothalamic brain stimulation, various natural rewards, and several drugs of abuse are attenuated by D1 or D2 dopamine receptor (D1R or D2R) antagonists. Much of the evidence for dopaminergic involvement in rewards is based on pharmacological agents with limited or "relative" selectivity for dopamine receptor subtypes. Genetically engineered animal models provide a complementary approach to pharmacological investigations., Objectives: In the present study, we explored the contribution of dopamine D2Rs to (1) brain stimulation reward (BSR) and (2) the potentiation of this behavior by morphine and amphetamine using D2R-deficient mice., Methods: Wild-type (D2Rwt), heterozygous (D2Rhet), and D2R knockout (D2Rko) mice were trained to turn a wheel for rewarding brain stimulation. Once equivalent rate-frequency curves were established, morphine-induced (0, 1.0, 3.0, and 5.6 mg/kg s.c.) and amphetamine-induced (0, 1.0, 2.0, and 4.0 mg/kg i.p.) potentiations of BSR were determined., Results: The D2Rko mice required approximately 50% more stimulation than the D2Rwt mice did. With the equi-rewarding levels of stimulation current, amphetamine potentiated BSR equally across the three genotypes. In contrast, morphine potentiated rewarding stimulation in the D2Rwt, had no effect in the D2Rhet, and antagonized rewarding stimulation in the D2Rko mice., Conclusions: D2R elimination decreases, but does not eliminate, the rewarding effects of lateral hypothalamic stimulation. After compensation for this deficit, amphetamine continues to potentiate BSR, while morphine does not.

A database of mouse locomotor path in spatial tests can be used to search in silico for behavioral measures that better discriminate between genotypes and are more replicable across laboratories. In this study, software for the exploration of exploration (SEE) was used to search a large database for a novel behavioral measure that would characterize complex movement paths. The database included mouse open-field behavior assessed in 3 laboratories, 7 inbred strains, several pharmacological treatments and hundreds of animals. The new behavioral measure, "path texture", was characterized using the local curvature of the path (the change of direction per unit distance, in degrees/cm) across several spatial scales, starting from scales smaller than the animal's body length and up to the scale of the arena size. Path texture analysis differs from fractal dimension analysis in that it does not assume self-similarity across scales. Path texture was found to discriminate inbred strains with relatively high broad-sense heritability (43%-71%) and high replicability across laboratories. Even genotypes that had similar path curvatures in some scales usually differed in other scales, and self-similarity across scales was not displayed by all genotypes. Amphetamine decreased the path curvature of C57BL/6 mice in small and medium scales, while having no effect on DBA/2J mice. Diazepam dose-dependently decreased the curvature of C57BL/6 mice across all scales, while 2 anxiogenic drugs, FG-7142 and pentylenetetrazole, increased it. Path texture thus has high potential for behavioral phenotyping and the study of drug effects in the mouse.

In behavior genetics, behavioral patterns of mouse genotypes, such as inbred strains, crosses, and knockouts, are characterized and compared to associate them with particular gene loci. Such genotype differences, however, are usually established in single-laboratory experiments, and questions have been raised regarding the replicability of the results in other laboratories. A recent multilaboratory experiment found significant laboratory effects and genotype x laboratory interactions even after rigorous standardization, raising the concern that results are idiosyncratic to a particular laboratory. This finding may be regarded by some critics as a serious shortcoming in behavior genetics. A different strategy is offered here: (i) recognize that even after investing much effort in identifying and eliminating causes for laboratory differences, genotype x laboratory interaction is an unavoidable fact of life. (ii) Incorporate this understanding into the statistical analysis of multilaboratory experiments using the mixed model. Such a statistical approach sets a higher benchmark for finding significant genotype differences. (iii) Develop behavioral assays and endpoints that are able to discriminate genetic differences even over the background of the interaction. (iv) Use the publicly available multilaboratory results in single-laboratory experiments. We use software-based strategy for exploring exploration (see) to analyze the open-field behavior in eight genotypes across three laboratories. Our results demonstrate that replicable behavioral measures can be practically established. Even though we address the replicability problem in behavioral genetics, our strategy is also applicable in other areas where concern about replicability has been raised.

Traditional open-field activity measures do not provide a sharp behavioral differentiation across psychomotor stimulants such as d-amphetamine (AMPH) and cocaine (COC) in the mouse. We used Software for the Exploration of Exploration (SEE) to investigate and develop a novel behavioral endpoint to characterize the "structure" of AMPH- and COC-induced locomotor behavior in two inbred strains of mouse, C57BL/6 (B6) and DBA/2 (D2). We suggest a measure we term "activity density" as a means to differentiate the behavioral effects of COC and AMPH. Activity density is defined as the activity divided by the range over which it took place. It characterizes the restriction of behavioral repertoire that does not result merely from inactivity. In both the B6 and D2 mice, AMPH increased activity density in a dose-dependent fashion by restricting the range of activity compared with COC doses producing the same level of activity. While AMPH restricted the range in both genotypes, characterizing the geographical region in which the restriction took place further differentiated the genotypes. The newly developed activity density measure thus provides a more general measure than stereotypy of the path, and can differentiate the effects of AMPH and COC both within and across genotypes.

Exposure to stress during gestation induces marked changes in the behavior of the affected offspring. Examining the consequences of prenatal stress may prove useful in understanding more about the origins of schizophrenia because a number of clinical investigations have suggested that developmental insults are associated with an increased incidence of schizophrenia. The purpose of these studies is to investigate the effects of stress during gestation on the behaviors of the adult male rat offspring with an emphasis on developing a heuristic animal model of schizophrenia. Pregnant female Sprague-Dawley rats were exposed to a novel variable stress paradigm during either the second or third week of gestation. Behavioral and neuroendocrinological consequences of prenatal stress exposure were evaluated in the male offspring on postnatal day 35 or 56. Prenatal stress exposure during the third week of pregnancy caused adult male rats to exhibit prolonged elevation in plasma glucocorticoid levels following acute exposure to restraint stress indicative of diminished glucocorticoid negative feedback. Similarly, exposure to stress during the third week of pregnancy elicited an enhanced locomotor response to the psychomotor stimulant amphetamine on postnatal day 56 but not on postnatal day 35. In addition, prepulse inhibition of the acoustic startle response was diminished across a range of prepulse stimulus intensities in prenatally stressed adult male rats. Similarly, prenatally stressed rats showed evidence of a disruption in auditory sensory gating as measured by the N40 response. Taken together, these findings suggest that prenatal stress exposure significantly changed many facets of adult rat behavior. Interestingly, the behaviors that are altered have been used to validate animal models of schizophrenia and therefore, suggest that this preparation may be useful to learn more about some aspects of the pathophysiology of schizophrenia.

Rationale: Sensorimotor gating disruption is one of many neurocognitive deficits seen in schizophrenia. Disorganized thought is one of the cardinal symptoms associated with sensorimotor gating. In an attempt to model sensorimotor gating deficits in rats relevant to the neurodevelopmental hypothesis for schizophrenia, we have used prenatal injections of the antimitotic drug, cytosine arabinoside (Ara-C) to subtly perturb the development of the rat CNS and disrupt sensorimotor gating., Objective: To produce rats with either basal sensorimotor gating deficits or increased vulnerability to the disruption of sensorimotor function by apomorphine or phencyclidine (PCP). Prepulse inhibition (PPI) of the acoustic startle response was used to assess sensorimotor gating., Methods: Three different cohorts of pregnant Sprague Dawley female rats were injected with Ara-C (30 mg/kg in saline) or saline at embryonic days 19.5 and 20.5. The Ara-C and control rats were tested for acoustic startle response and PPI at preadolescent and post-adolescent ages; postnatal day (Pnd) 35 and 56, respectively. Apomorphine (2.0 mg/kg) or phencyclidine (3.0 mg/kg), was given prior to PPI sessions in order to disrupt PPI., Results: At Pnd 35, Ara-C treatment did not significantly affect acoustic startle amplitudes or PPI. However, at PND 56, Ara-C treated rats had significantly lower acoustic startle amplitudes and significantly diminished sensorimotor gating. Pharmacological challenge with the dopamine agonist apomorphine and the glutamate antagonist PCP significantly disrupted sensorimotor gating in the control subjects. Apomorphine did not further disrupt the existing deficit in the Ara-C treated rats. Ara-C treatment did not cause gross loss of neuronal tissue, although there was a subtle and variable disorganization of the pyramidal cell layer in the hippocampal CA2/3 region., Conclusion: The results provide evidence to suggest that late embryonic exposure to Ara-C disrupts the circuitry involved in mediating PPI. While the dopamine agonist apomorphine caused a significant disruption in the control rats it did not further disrupt the existing deficit in the Ara-C treated rats. These data provide evidence to support the contention that modest neurodevelopmental insults can significantly affect sensorimotor gating processes in an adult onset dependent manner.

Anxiety is a widely studied psychiatric disorder and is thought to be a complex and multidimensional phenomenon. Sensitive behavioral discrimination of animal models of anxiety is crucial for the elucidation of the behavioral components of anxiety and the physiological processes that mediate them. Commonly used behavior paradigms of anxiety usually include only a few automatically collected measures; these do not exhaust the behavioral richness exhibited by animals, thus perhaps missing important differences between preparations. The aim of the present study was to expand the repertoire of automatically collected measures in a classical test of anxiety: behavior in relation to the wall in the open field. We present an algorithm, based on the Software for the Exploration of Exploration strategy, which automatically partitions the mouse path into intrinsically defined patterns of movement near the wall and in the center. These patterns are used to design new end points, which provide an articulated description of various aspects of behavior near the wall and in the center. Sixteen new end points were designed with data from C57BL/6J and DBA/2J mice tested in three laboratories. The strain differences in all end points were evaluated on another data set to assess their validity and were found to remain stable. Ten of the sixteen end points were found to discriminate between the two strains in a replicable manner. The entire set of end points can be used on various genetic and pharmacological models of anxiety with good prospects of providing fine discrimination in a replicable manner.

Rationale: Previous studies have found a role for dopamine D(2)-like receptors in many of the behavioral effects of cocaine, including its stimulation of locomotor activity and interoceptive discriminative-stimulus effects. However, given the lack of selectivity of most of the available pharmacological tools among D(2), D(3) and D(4) dopamine receptors, the roles of these specific receptors remain unclear., Objectives: The roles of specific dopamine D(4) receptors in the behavioral effects of cocaine, including its locomotor stimulant and interoceptive discriminative-stimulus effects were investigated using dopamine D(4) receptor knockout (DA D(4)R KO) and wild-type (WT) mice., Methods: The mice were trained in daily sessions to discriminate IP injections of saline from cocaine (10 mg/kg). Responses on one of two response keys intermittently produced a food pellet; one response was reinforced in sessions following cocaine injection (10 mg/kg), and the other response was reinforced in sessions following saline injection. Each 20th response produced a food pellet (fixed-ratio, or FR20 schedule of reinforcement). The dose-effects of cocaine and its interaction with the D(2)-like antagonist, raclopride, were assessed. Horizontal locomotor activity was also assessed in each genotype., Results: As previously shown), cocaine was a more potent stimulant of locomotor activity in the DA D(4)R KO mice compared to WT littermate mice. In addition, cocaine was more potent in producing discriminative-stimulus effects in DA D(4)R KO mice (ED(50) value=0.50 mg/kg) compared to their WT littermates (ED(50) value=2.6 mg/kg). Raclopride shifted the cocaine dose-effect curve in both DA D(4)R KO and WT mice, though the shift was greater for the DA D(4)R KO mice., Conclusions: The present results on the stimulation of activity and interoceptive/subjective effects of cocaine are consistent with the previously reported disregulation of dopamine synthesis in DA D(4)R KO mice, and further suggest a role of the DA D(4)R in vulnerability to stimulant abuse.

In the open-field behavior of rodents, Software for Exploring Exploration (SEE) can be used for an explicit design of behavioral endpoints with high genotype discrimination and replicability across laboratories. This ability is demonstrated here in the development of a measure for darting behavior. The behavior of two common mouse inbred strains, C57BL/6J (B6) and DBA/2J (D2), was analyzed across three different laboratories, and under the effect of cocaine or amphetamine. "Darting" was defined as having higher acceleration during progression segments while moving less during stops. D2 mice darted significantly more than B6 mice in each laboratory, despite being significantly less active. These differences were maintained following cocaine administration (up to 20mg/kg) and only slightly altered by amphetamine (up to 5mg/kg) despite a several fold increase in activity. The replicability of darting behavior was confirmed in additional experiments distinct from those used for its design. The strategy leading to the darting measure may be used to develop additional discriminative and replicable endpoints of open-field behavior.

Conventional tests of behavioral phenotyping frequently have difficulties differentiating certain genotypes and replicating these differences across laboratories and protocol conditions. This study explores the hypothesis that automated tests can be designed to quantify ethologically relevant behavior patterns that more readily characterize heritable and replicable phenotypes. It used SEE (Strategy for the Exploration of Exploration) to phenotype the locomotor behavior of the C57BL/6 and DBA/2 mouse inbred strains across 3 laboratories. The 2 genotypes differed in 15 different measures of behavior, none of which had a significant genotype-laboratory interaction. Within the same laboratory, most of these differences were replicated in additional experiments despite the test photoperiod phase being changed and saline being injected. Results suggest that well-designed tests may considerably enhance replicability across laboratories.

Rationale: Dopamine (DA) D2-like antagonists block several effects of cocaine, including its locomotor stimulant and interoceptive discriminative-stimulus effects. Because these compounds generally lack selectivity among the D2-like DA receptors, the specific roles of the subtypes remain unclear., Objectives: DA D2 receptor knockout (DA D2R KO), heterozygous (HET), and wild-type (WT) mice were used to study the role of D2 DA receptors in the effects of cocaine. Some effects of the relatively selective DA D2-like antagonist raclopride were also studied to further assess the role of D2 receptors., Methods: DA D2R KO, HET, and WT mice were treated with cocaine (1-10 mg/kg) or vehicle, and their horizontal locomotor activity was assessed. The mice were also trained to discriminate i.p. injections of saline from cocaine (10 mg/kg) using a two-response key, fixed-ratio-20 response, food-reinforcement procedure. A range of doses of cocaine (1.0-17 mg/kg) was administered before 15-min test sessions., Results: Both DA D2R KO and HET mice showed reduced levels of horizontal activity relative to WT mice. Cocaine dose dependently stimulated activity in each genotype, with the highest level of activity induced in the DA D2R WT mice. All three genotypes acquired the discrimination of 10 mg/kg cocaine; tested doses of 1.0-10.0 mg/kg produced dose-related increases in the number of cocaine-appropriate responses. Raclopride, at inactive to fully active doses (0.1-1.0 mg/kg), did not fully substitute for cocaine. Raclopride dose dependently shifted the cocaine dose-effect curve to the right in DA D2R WT and HET mice. However, in DA D2R KO mice, raclopride was inactive as an antagonist., Conclusions: The present data indicate an involvement of D2 DA receptors in the locomotor-stimulating effects and the interoceptive discriminative-stimulus effects of cocaine in WT subjects. However, the D2 receptor is not necessary for the effects, suggesting redundant dopaminergic mechanisms for the discriminative-stimulus interoceptive effects of cocaine.

The rewarding effects of opiates are thought to be mediated through dopaminergic mechanisms in the ventral tegmental area, dopamine-independent mechanisms in the nucleus accumbens, or both. The purpose of the present study was to explore the contribution of dopamine to opiate-reinforced behavior using D2 receptor knock-out mice. Wild-type, heterozygous, and D2 knock-out mice were first trained to lever press for water reinforcement and then implanted with intravenous catheters. The ability of intravenously delivered morphine to maintain lever pressing in these mice was studied under two schedules of reinforcement: a fixed ratio 4 (FR4) schedule (saline, 0.1, 0.3, or 1.0 mg/kg, per injection) and a progressive ratio (PR) schedule (1.0 mg/kg, per injection). In the wild-type and heterozygous mice, FR4 behavior maintained by morphine injections was significantly greater than behavior maintained by vehicle injections. Response rate was inversely related to injection dose and increased significantly in the wild-type and heterozygous mice when the animals were placed on the PR schedule. In contrast, the knock-out mice did not respond more for morphine than for saline and did not respond more when increased ratios were required by the PR schedule. Thus, morphine served as a positive reinforcer in the wild-type and heterozygous mice but failed to do so in the knock-out mice. Under this range of doses and response requirements, the rewarding effects of morphine appear to depend critically on an intact D2 receptor system.

Preclinical evidence suggests there is a link between the responsiveness to stress and the propensity to self-administer drugs of abuse. Our previous findings, for example, have shown a significant positive correlation between the locomotor response to novelty and the acquisition of morphine self-administration in Lewis (LEW), Fischer 344 (F344) and ACI inbred rat strains. As an extension of this work, we now report on the neuroendocrine responses (i.e., corticosterone and prolactin secretion) evoked by morphine administration in these same inbred strains. Male LEW, F344, and ACI rats were surgically prepared with indwelling jugular catheters 7 days prior to the study. Following a habituation period, rats were treated with i.p. saline or morphine (1, 5 or 10 mg/kg). Repeated blood samples were withdrawn via the catheters immediately before and at 20, 40, 60 and 120 min after injection. Plasma samples were assayed for hormone levels by radioimmunoassay. No differences in baseline corticosterone levels were found across strains. There was a significant effect of genotype on the corticosterone response to saline injection (i.e., mild stress), with F344 rats exhibiting sustained elevations in corticosterone compared to LEW and ACI rats. Morphine-induced stimulation of corticosterone release differed significantly across strains, and in this case LEW rats displayed a reduced sensitivity to morphine. Similar to the corticosterone results, LEW rats also had blunted prolactin responses to morphine when compared to F344 rats. Our data demonstrate that genotype is an important factor modulating the neuroendocrine sensitivity to morphine. It is noteworthy that LEW rats acquire self-administration more rapidly than F344 or ACI rats, yet LEW rats display reduced corticosterone responses to stress and morphine. Taking into account the particular conditions of this study (high i.p. doses used here vs. low i.v. doses in self-administration studies), our results do not suggest that corticosterone response to stress and morphine is related to vulnerability to intravenous opiate self-administration. The data, however, are consistent with the idea of that genetic factors might influence the sensitivity to the morphine-induced effects of glucocorticoids across these inbred strains.