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Rationale: 4-Iodo-2,5-dimethoxy-N-(2-methoxybenzyl)phenethylamine (25I-NBOMe) is a potent serotonin 5-HT 2A/2C receptor agonist with hallucinogenic activity. There is no data on the 25I-NBOMe effect on brain neurotransmission and animal performance after chronic administration., Objectives: We examined the effect of a 7-day treatment with 25I-NBOMe (0.3 mg/kg/day) on neurotransmitters' release and rats' behavior in comparison to acute dose., Methods: Changes in dopamine (DA), serotonin (5-HT), acetylcholine (ACh), and glutamate release were studied using microdialysis in freely moving rats. The hallucinogenic activity was measured in the wet dog shake (WDS) test. The animal locomotion was examined in the open field (OF) test, short-term memory in the novel object recognition (NOR) test. The anxiogenic/anxiolytic properties of the drug were tested using the light/dark box (LDB) test., Results: Repeated administration of 25I-NBOMe decreased the response to a challenge dose of DA, 5-HT, and glutamatergic neurons in the frontal cortex as well as weakened the hallucinogenic activity in comparison to acute dose. In contrast, striatal and accumbal DA and 5-HT release and accumbal but not striatal glutamate release in response to the challenge dose of 25I-NBOMe was increased in comparison to acute treatment. The ACh release was increased in all brain regions. Behavioral tests showed a motor activity reduction and memory deficiency in comparison to a single dose and induction of anxiety after the drug's chronic and acute administration., Conclusions: Our findings suggest that multiple injections of 25I-NBOMe induce tolerance to hallucinogenic activity and produce alterations in neurotransmission. 25I-NBOMe effect on short-term memory, locomotor function, and anxiety seems to be the result of complex interactions between neurotransmitter pathways., (© 2021. The Author(s).)

Rationale: Gambling disorder is a growing societal concern, as recognized by its recent classification as an addictive disorder in the DSM-5. Case reports have shown that disulfiram reduces gambling-related behavior in humans., Objectives: The purpose of the present study was to determine whether disulfiram affects performance on a rat gambling task, a rodent version of the Iowa gambling task in humans, and whether any changes were associated with alterations in dopamine and/or norepinephrine levels., Methods: Rats were administered disulfiram prior to testing on the rat gambling task or prior to analysis of dopamine or norepinephrine levels in brain homogenates. Rats in the behavioral task were divided into two subgroups (optimal vs suboptimal) based on their baseline levels of performance in the rat gambling task. Rats in the optimal group chose the advantageous strategy more, and rats in the suboptimal group (a parallel to problem gambling) chose the disadvantageous strategy more. Rats were not divided into optimal or suboptimal groups prior to neurochemical analysis., Results: Disulfiram administered 2 h, but not 30 min, before the task dose-dependently improved choice behavior in the rats with an initial disadvantageous "gambling-like" strategy, while having no effect on the rats employing an advantageous strategy. The behavioral effects of disulfiram were associated with increased striatal dopamine and decreased striatal norepinephrine., Conclusions: These findings suggest that combined actions on dopamine and norepinephrine may be a useful treatment for gambling disorders.

Rationale: Depression associated with obesity remains an interesting area to study the biological mechanisms and novel therapeutic intervention., Objectives: The present study investigates the effect of a novel 5-HT 3 receptor antagonist 3-methoxy-N-p-tolylquinoxalin-2-carboxamide (QCM-4) on several pathogenic markers of depression associated with obesity such as plasma insulin resistance, hippocampal cyclic adenosine monophosphate (cAMP), brain-derived neurotrophic factor (BDNF), serotonin (5-HT) concentrations, hippocampal neuronal damage, and p53 protein expression in high-fat-diet (HFD)-fed mice., Methods: Obesity was experimentally induced in mice by feeding with HFD for 14 weeks followed by administration of QCM-4 (1 and 2 mg/kg, p.o.)/standard escitalopram (ESC) (10 mg/kg, p.o.)/vehicle (10 ml/kg, p.o.) for 28 days. Behavioral assays such as sucrose preference test (SPT); forced swim test (FST); elevated plus maze (EPM); biochemical assays including oral glucose tolerance tests (OGTT), insulin, cAMP, BDNF, and 5-HT concentrations; and molecular assays mainly histology and immunohistochemistry (IHC) of p53 protein in the dentate gyrus (DG), CA1, and CA3 regions of hippocampus in HFD fed mice were performed., Results: Chronic treatment with QCM-4 in HFD-fed mice reversed the behavioral alterations in SPT, FST, and EPM. QCM-4 showed poor sensitivity for plasma glucose, improved insulin sensitivity, increased hippocampal cAMP, BDNF, and 5-HT concentrations. In the hippocampal DG, CA1, and CA3 regions, QCM-4 treatment improved the neuronal morphology in the histopathology and inhibited p53 protein expression in IHC assay in HFD-fed mice., Conclusion: QCM-4 attenuated the depressive-like phenotype in HFD-fed mice by improving behavioral, biochemical, and molecular alterations through serotonergic neuromodulation.

Rationale and Objectives: Alpha-1 adrenoceptor antagonists, such as prazosin, show promise in treating alcoholism. In rats, prazosin reduces alcohol self-administration and relapse induced by footshock stress and the alpha-2 antagonist yohimbine, but the processes involved in these effects of prazosin are not known. Here, we present studies on the central mechanisms underlying the effects of prazosin on yohimbine-induced reinstatement of alcohol seeking., Methods: In experiment 1, we trained rats to self-administer alcohol (12 % w/v, 1 h/day), extinguished their responding, and tested the effects of prazosin, administered ICV (2 and 6 nmol) or systemically (1 mg/kg) on yohimbine (1.25 mg/kg)-induced reinstatement. In experiment 2, we determined potential central sites of action by analyzing effects of prazosin (1 mg/kg) on yohimbine (1.25 mg/kg)-induced Fos expression. In experiment 3, we determined the effects of doxazosin (1.25, 2.5, and 5 mg/kg), an alpha-1 antagonist with a longer half-life on yohimbine-induced reinstatement., Results: Yohimbine-induced reinstatement of alcohol seeking was reduced significantly by ICV and systemic prazosin (50 and 69 % decreases, respectively). Systemic prazosin reduced yohimbine-induced Fos expression in the prefrontal cortex, accumbens shell, ventral bed nucleus of the stria terminalis, and basolateral amygdala (46-67 % decreases). Doxazosin reduced yohimbine-induced reinstatement of alcohol seeking (78 % decrease)., Conclusions: Prazosin acts centrally to reduce yohimbine-induced alcohol seeking. The Fos mapping study suggests candidate sites where it may act. Doxazosin is also effective in reducing yohimbine-induced reinstatement. These data provide information on the mechanisms of alpha-1 antagonists on yohimbine-induced alcohol seeking and indicate their further investigation for the treatment of alcoholism.

Rationale: Dopamine plays a critical role in striatal and cortical function, and depletion of the dopamine precursors phenylalanine and tyrosine is used in humans to temporarily reduce dopamine and probe the role of dopamine in behavior. This method has been shown to alter addiction-related behaviors and cognitive functioning presumably by reducing dopamine transmission, but it is unclear what specific aspects of dopamine transmission are altered., Objectives: We performed this study to confirm that administration of an amino acid mixture omitting phenylalanine and tyrosine (Phe/Tyr[-]) reduces tyrosine tissue content in the prefrontal cortex (PFC) and nucleus accumbens (NAc), and to test the hypothesis that Phe/Tyr[-] administration reduces phasic dopamine release in the NAc., Methods: Rats were injected with a Phe/Tyr[-] amino acid mixture, a control amino acid mixture, or saline. High-performance liquid chromatography was used to determine the concentration of tyrosine, dopamine, or norepinephrine in tissue punches from the PFC and ventral striatum. In a separate group of rats, phasic dopamine release was measured with fast-scan cyclic voltammetry in the NAc core after injection with either the Phe/Tyr[-] mixture or the control amino acid solution., Results: Phe/Tyr[-] reduced tyrosine content in the PFC and NAc, but dopamine and norepinephrine tissue content were not reduced. Moreover, Phe/Tyr[-] decreased the frequency of dopamine transients, but not their amplitude, in freely moving rats., Conclusions: These results indicate that depletion of tyrosine via Phe/Tyr[-] decreases phasic dopamine transmission, providing insight into the mechanism by which this method modifies dopamine-dependent behaviors in human imaging studies.

Rationale: Reserpine, a monoamine-depleting agent, which irreversibly and non-selectively blocks the vesicular monoamine transporter, has been used as an animal model to study several neurological disorders, including tardive dyskinesia and Parkinson's disease., Objective: The purpose of this study was to examine if motor deficits induced by reserpine in mice could be related to alterations in the expression of dopaminergic system proteins such as tyrosine hydroxylase (TH) and dopamine transporter (DAT) and in the activity of monoamine oxidase (MAO)., Methods: Mice received either vehicle or reserpine (0.1, 0.5, or 1 mg/kg, s.c.) for four consecutive days. Two, 20, or 60 days after reserpine withdrawal, behavioral, and neurochemical changes were evaluated., Results: Reserpine at a dose of 0.5 and 1 mg/kg increased vacuous chewing movements (VCMs) and reduced locomotion. Behavioral changes were accompanied by reduction in TH immunoreactivity in the striatum evaluated on days 2 and 20 after the last injection of 1 mg/kg reserpine. Furthermore, negative correlations were found between VCM and MAO-A or MAO-B on day 2 and TH striatal immunoreactivity on day 20 after the last injection of 1 mg/kg reserpine. A positive correlation was observed between VCMs and DAT immunoreactivity in the substantia nigra on day 2 after the last injection of 0.5 mg/kg reserpine., Conclusions: These findings suggest that the pharmacological blockage of vesicular monoamine transporter (VMAT) by reserpine caused neurochemical and behavioral alterations in mice.

Rationale: The acetylcholinesterase inhibitors donepezil, galantamine, and rivastigmine are used for the treatment of Alzheimer's disease. We previously demonstrated that donepezil and galantamine differentially affect isolation rearing-induced prepulse inhibition (PPI) deficits and that this might be due to differential effects on brain muscarinic acetylcholine (mACh) receptor function in mice., Objectives: We examined the effects of rivastigmine on isolation rearing-induced PPI deficits, brain ACh levels, and mACh receptor function in mice., Methods: Acoustic startle responses were measured in a startle chamber. Microdialysis was performed, and the levels of dopamine and ACh in the prefrontal cortex were measured., Results: Rivastigmine (0.3 mg/kg) improved PPI deficits, and this improvement was antagonized by the mACh receptor antagonist telenzepine but not by the nicotinic ACh receptor antagonist mecamylamine. Rivastigmine increased extracellular ACh levels by approximately 2-3-fold, less than the increase produced by galantamine. Rivastigmine enhanced the effect of the mACh receptor agonist N-desmethylclozapine on prefrontal dopamine release, a marker of mACh receptor function, and this increase was blocked by telenzepine. In contrast, galantamine did not affect N-desmethylclozapine-induced dopamine release. Furthermore, rivastigmine did not affect cortical dopamine release induced by the serotonin1A receptor agonist osemozotan, suggesting that the effect of rivastigmine has specificity for mACh receptors., Conclusions: Taken together with our previous finding that marked increases in ACh levels are required for the PPI deficit improvement induced by galantamine, our present results suggest that rivastigmine improves isolation rearing-induced PPI deficits by increasing ACh levels and by concomitantly enhancing mACh receptor function.

Rationale: The zebrafish has become an increasingly popular animal model for investigating ethanol's actions in the brain and its effects on behavior. Acute exposure to ethanol in zebrafish has been shown to induce a dose-dependent increase of locomotor activity, to reduce fear- and anxiety-related behavioral responses, and to increase the levels of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC)., Objectives: The objective of the present study was to investigate the role of dopamine D1 receptors (D1-R) in ethanol-induced locomotor activity in zebrafish., Methods: Zebrafish were pre-treated with SCH-23390 (0 or 1 mg/L bath concentration), a D1-R antagonist, and subsequently exposed to ethanol (0, 0.25, 0.5, 1.0 % v/v). To explore potential underlying mechanisms, we quantified levels of dopamine, DOPAC, serotonin, and 5-HIAA from whole-brain tissue using high-precision liquid chromatography., Results: We found pre-treatment with the D1-R antagonist to attenuate locomotor activity independent of ethanol concentration. Furthermore, unlike ethanol, D1-R antagonism did not alter behavioral responses associated with fear and anxiety. Pre-treatment with SCH-23390 decreased levels of dopamine and DOPAC, but this effect was also independent of ethanol concentration. The D1-R antagonist also reduced serotonin and 5-hydroxyindole acetic acid (5-HIAA) levels., Conclusion: These results suggest a multifaceted and at least partially independent role of dopamine D1 receptors in ethanol-induced locomotor activity and anxiety-related responses as well as in the functioning of the dopaminergic and serotoninergic neurotransmitter systems in zebrafish.

Rationale: L-dopa, the main therapeutic for Parkinson's disease (PD), has been shown to increase brain dopamine concentrations that are necessary for proper motor control; however, PD patients experience non-motor symptoms that are not improved or could be exacerbated by L-dopa., Objectives: The purpose of this study is to determine the effects of L-dopa treatment on cognitive and affective behavioral responses of rats, as well as their corresponding monoamine brain concentrations., Methods: Rats were treated with L-dopa (6 mg/kg; twice daily) for 10 consecutive days. Sodium ascorbate (400 mg/kg) was co-administered with L-dopa to investigate the effects of antioxidant co-treatment on behavior and monoamine concentrations. Rats underwent cognitive and affective behavioral testing. Monoamine concentrations of several brain regions were analyzed., Results: L-dopa treatment resulted in significant impairment in the performance in the Barnes maze and improvement in conditioned fear stress paradigms. Specifically, L-dopa caused an increase in latency to find the goal box during Barnes maze testing and increased freezing behavior in context-induced conditioned fear testing. Furthermore, the rats in the conditioned fear stress experiments showed corresponding depletions in serotonin (5-HT) and its metabolite, 5-HIAA, in the dorsal raphe nucleus (DRN) and the mPFC. The behavioral impairments as well as monoamine depletions were blocked by ascorbate co-treatment., Conclusions: Chronic L-dopa may contribute to non-motor symptoms related to spatial memory and fear. These effects may be attributable to a dysregulation of brain 5-HT caused by L-dopa treatment. The results presented here provide further rationale for investigating adjunctive therapeutics to L-dopa for PD, such as antioxidants.

The Disrupted-in-schizophrenia 1 (DISC1) gene is involved in vulnerability to neuropsychiatric disorders. Naples high-excitability (NHE) rat model neuropsychiatric problems characterized by an unbalanced mesocortical dopamine system. Here, we assessed behavioral and neurochemical effects of immunization against multimeric rat DISC1 protein in adult NHE rats, an animal model of attention-deficit hyperactivity disorder and their Random-Bred (NRB) controls. Males of both lines received subcutaneous injections of vehicle (PB), adjuvant only (AD) or recombinant rat DISC1 protein purified from E. coli, suspended in AD (anti-DISC1) at age of 30, 45 and 60 postnatal days (pnd). At 75 pnd, the rats were exposed to a Làt maze and 2 days later to an Olton eight-arm radial maze, and horizontal (HA) and vertical activities (VA) were monitored. Non-selective (NSA) and selective spatial attention (SSA) were monitored in the Làt and in the Olton maze by duration of rearings and working memory, respectively. Post mortem neurochemistry in the prefrontal cortex (PFc), dorsal (DS) and ventral (VS) striatum of L-Glutamate, L-Aspartate and L-Leucine was performed. All immunized rats showed a clear humoral IgM (but not IgG) immune response against the immunogen, indicating that immunological self-tolerance to DISC1 can be overcome by immunization. NHE rats exhibited a higher unspecific IgM response to adjuvant, indicating an immunological abnormality. The sole anti-DISC1 immunization-specific behavioral in the NHE rats was an increased horizontal activity in the Làt maze. Adjuvant treatment increased vertical activity in both lines, but in the NRB controls it increased rearing and decreased horizontal activity. Liquid chromatography/tandem mass spectrometry analysis of soluble or membrane-trapped neurotransmitters aspartate, glutamate and leucine revealed increased soluble aspartate levels in the ventral striatum of NRB controls after anti-DISC1 immunization. Immune activation by adjuvant independent of simultaneous DISC1 immunization led to other specific changes in NHE and control NRB rats. In DISC1-immunized NHE rats, horizontal activity in Lat maze correlated with membrane-trapped glutamate in PFc and in the NRB rats, duration of rearing in Olton maze correlated with membrane-trapped glutamate in PFc and aspartate in dorsal striatum. In addition to non-specific immune activation (by AD), the postnatal anti-DISC1 immune treatment led to behavioral changes related to mechanisms of activity and attention and had influenced amino acids and synaptic markers in striatum and neocortex in the adult NHE as well as control animals.

Rationale: Salvinorin A is a recreational drug derived from Salvia divinorum, a sage species long used as an entheogen. While salvinorin A has potent hallucinogenic properties, its abuse potential has not been assessed consistently in controlled behavioural and neurochemical studies in rodents., Objective: This study aimed to assess salvinorin A abuse potential by measuring its capacity to establish and maintain self-administration behaviour and to modify dopamine (DA) levels in the nucleus accumbens (NAcc) of rats., Results: Male Lister Hooded (LH) and Sprague-Dawley (SD) rats were allowed to self-administer salvinorin A (0.5 or 1.0 μg/kg/infusion) intravenously 2 h/day for 20 days under a continuous schedule of reinforcement and lever pressing as operandum. LH rats discriminated between the active and inactive levers but did not reach the acquisition criterion for stable self-administration (≥12 active responses vs ≤5 inactive responses for at least 5 consecutive days). SD rats discriminated between the two levers at the lower dose only but, like LH rats, never acquired stable self-administration behaviour. Systemic salvinorin A increased extracellular DA in the NAcc shell of both LH (at ≥40 μg/kg) and SD rats (at ≥5 μg/kg), but injection into the ventral tegmental area (VTA) induced no significant change in NAcc DA concentration in LH rats and only brief elevations in SD rats., Conclusions: Salvinorin A differs from other commonly abused compounds since although it affects accumbal dopamine transmission, yet it is unable, at least at the tested doses, to sustain stable intravenous self-administration behaviour.

Rationale: Stress activates the hypothalamic-pituitary-adrenal (HPA) axis, and GABAergic neuroactive steroids contribute to homeostatic regulation of this circuitry. Acute forced swim stress (FSS) increases plasma, cortical, and hypothalamic (3α,5α)-3-hydroxy-pregnan-20-one (3α,5α-THP) levels in rats. However, there have not been systemic investigations of acute stress on changes in plasma and brain levels of 3α,5α-THP in mouse models., Objectives: The present experiments aimed to assess circulating and local brain levels of 3α,5α-THP following acute FSS in C57BL/6J mice., Methods: Mice were exposed to FSS (10 min), and 50 min later, blood and brains were collected. Circulating pregnenolone and 3α,5α-THP levels were assessed in serum. Free-floating brain sections (40 μm, four to five sections/region) were immunostained and analyzed in cortical and limbic brain structures., Results: FSS decreased circulating 3α,5α-THP (-41.6 ± 10.4 %) and reduced 3α,5α-THP immunolabeling in the paraventricular nucleus of the hypothalamus (-15.2 ± 5.7 %), lateral amygdala (LA, -31.1 ± 13.4 %), and nucleus accumbens (NAcc) shell (-31.9 ± 14.6). Within the LA, vesicular glutamate transporter 1 (VGLUT1) and vesicular GABA transporter were localized in 3α,5α-THP-positively stained cells, while in the NAcc shell, only VGLUT1 was localized in 3α,5α-THP-positively stained cells, suggesting that both glutamatergic and GABAergic cells within the LA are 3α,5α-THP-positive, while in the NAcc shell, 3α,5α-THP only localizes to glutamatergic cells., Conclusions: The decrease in circulating and brain levels of 3α,5α-THP may be due to alterations in the biosynthesis/metabolism or changes in the regulation of the HPA axis following FSS. Changes in GABAergic neuroactive steroids in response to stress likely mediate functional adaptations in neuronal activity. This may provide a potential targeted therapeutic avenue to address maladaptive stress responsivity.

Rationale: Chronic stress or hypercortisolism may increase the risks of depression, cardiac disorders, and osteoporosis, which are also associated with vitamin D (VD) deficiency. Both glucocorticoid receptor (GR) and vitamin D receptor (VDR) are widely distributed and affect many aspects of human physiology. The cross talk between the two steroids is pervasive, but the effect of glucocorticoids on circulating VD and local VD metabolism remains elusive., Objectives: To fill this critical gap, we assessed the alterations of circulating VD and VD intracrine system in the brain and myocardium of rats treated with two different doses (0.2 and 2 mg/kg/day, respectively) of dexamethasone (Dex)., Results: Daily treatment with 2 mg/kg of Dex for 10 days induced the rats to a depressive-like state and decreased the expression of both VDR and the cytochromes P450 enzymes involved in VD activation (CYP27B1) and catabolism (CYP24A1) in the prefrontal cortex and hippocampus. Meanwhile, the dose of 0.2 mg/kg Dex increased the expression of VDR in the prefrontal cortex but inhibited CYP27B1/CYP24A1/VDR expression in the hippocampus. Similarly, in the myocardium, the rats treated with Dex showed significantly lower expression of CYP27B1/CYP24A1/VDR. Renal VD metabolism and serum VD status were unchanged in 0.2 mg/kg Dex-treated rats. However, the higher dose suppressed the three key players involved in VD metabolism but did not alter serum VD levels., Conclusion: These data provide new evidence that glucocorticoids could affect intracrine actions of VD in the brain and myocardium, which suggests the potential involvement of VD in the neural and cardiac dysfunctions induced by glucocorticoid excess.

Rationale: Neuroactive steroids are endogenous or synthetic steroids that rapidly alter neuronal excitability via membrane receptors, primarily γ-aminobutyric acid type A (GABAA) receptors. Neuroactive steroids regulate many physiological processes including hypothalamic-pituitary-adrenal (HPA) axis function, ovarian cycle, pregnancy, aging, and reward. Moreover, alterations in neuroactive steroid synthesis are implicated in several neuropsychiatric disorders., Objectives: This review will summarize the pharmacological properties and physiological regulation of neuroactive steroids, with a particular focus on divergent neuroactive steroid responses to stress and ethanol in rats, mice, and humans., Results: GABAergic neuroactive steroids exert a homeostatic regulation of the HPA axis in rats and humans, whereby the increase in neuroactive steroid levels following acute stress counteracts HPA axis hyperactivity and restores homeostasis. In contrast, in C57BL/6J mice, acute stress decreases neurosteroidogenesis and neuroactive steroids exert paradoxical excitatory effects upon the HPA axis. Rats, mice, and humans also differ in the neuroactive steroid responses to ethanol. Genetic variation in neurosteroidogenesis may explain the different neuroactive steroid responses to stress or ethanol., Conclusions: Rats and mouse strains show divergent effects of stress and ethanol on neuroactive steroids in both plasma and brain. The study of genetic variation in the various processes that determine neuroactive steroids levels as well as their effects on cell signaling may underlie these differences and may play a relevant role for the potential therapeutic benefits of neuroactive steroids.

Rationale: Ventricular enlargement is a robust phenotype of the chronically dependent alcoholic human brain, yet the mechanism of ventriculomegaly is unestablished. Heterogeneous stock Wistar rats administered binge EtOH (3 g/kg intragastrically every 8 h for 4 days to average blood alcohol levels (BALs) of 250 mg/dL) demonstrate profound but reversible ventricular enlargement and changes in brain metabolites (e.g., N-acetylaspartate (NAA) and choline-containing compounds (Cho))., Objectives: Here, alcohol-preferring (P) and alcohol-nonpreferring (NP) rats systematically bred from heterogeneous stock Wistar rats for differential alcohol drinking behavior were compared with Wistar rats to determine whether genetic divergence and consequent morphological and neurochemical variation affect the brain's response to binge EtOH treatment., Methods: The three rat lines were dosed equivalently and approached similar BALs. Magnetic resonance imaging and spectroscopy evaluated the effects of binge EtOH on brain., Results: As observed in Wistar rats, P and NP rats showed decreases in NAA. Neither P nor NP rats, however, responded to EtOH intoxication with ventricular expansion or increases in Cho levels as previously noted in Wistar rats. Increases in ventricular volume correlated with increases in Cho in Wistar rats., Conclusions: The latter finding suggests that ventricular volume expansion is related to adaptive changes in brain cell membranes in response to binge EtOH. That P and NP rats responded differently to EtOH argues for intrinsic differences in their brain cell membrane composition. Further, differential metabolite responses to EtOH administration by rat strain implicate selective genetic variation as underlying heterogeneous effects of chronic alcoholism in the human condition.

Rationale and Objectives: The effects of low thyroid hormone level during embryogenesis on MRI of the brain and social behaviors of hatchlings were examined using "fertilized hen's egg-embryo-chick" system., Methods and Results: Control and hatchlings treated with methimazole (20 μmol/egg), which hatched 3 days later than controls were examined. The results are as follows: 1. The MRI examination of the midsagittal section of the brain on hatch day showed that the sizes, by T1- and ADC values by diffusion-weighted images, of the optic lobe and cerebellum of the MMI-hatchlings were significantly bigger than those of the controls. 2. The social behaviors on post-hatch day 3 were based on the following tests: (a) Aggregation test: The speed of four chicks, individually isolated by cardboard barriers in a box, to make a group upon the removal of barriers. (b) Belongingness tests: The speed of a chick isolated at a corner to join the group of three chicks placed at the opposite corner. (c) Vocalization test: The number of decibel produced by a chick isolated at a corner using a sound meter. These tests demonstrated that MMI-hatchlings took longer times and had weaker vocalization than the controls, significantly. 3. Upregulation of THRβ mRNA after MMI treatment suggested that THR was necessary for cerebellum development., Conclusions: The MMI exposure during the last week of embryogenesis possibly delayed the myelination of certain brain regions and impaired the social behaviors of hatchlings. The chick embryos can be easily induced with hypothyroidism without maternal influences, and the hatchling's behaviors were analyzed using a video camera. The present method will be useful for assessing the effects of unfavorable influences during embryogenesis on social behaviors in later life.

The ingestion of large neutral amino acids (LNAA), notably tryptophan, tyrosine and the branched-chain amino acids (BCAA), modifies tryptophan and tyrosine uptake into brain and their conversion to serotonin and catecholamines, respectively. The particular effect reflects the competitive nature of the transporter for LNAA at the blood-brain barrier. For example, raising blood tryptophan or tyrosine levels raises their uptake into brain, while raising blood BCAA levels lowers tryptophan and tyrosine uptake; serotonin and catecholamine synthesis in brain parallel the tryptophan and tyrosine changes. By changing blood LNAA levels, the ingestion of particular proteins causes surprisingly large variations in brain tryptophan uptake and serotonin synthesis, with minimal effects on tyrosine uptake and catecholamine synthesis. Such variations elicit predictable effects on mood, cognition and hormone secretion (prolactin, cortisol). The ingestion of mixtures of LNAA, particularly BCAA, lowers brain tryptophan uptake and serotonin synthesis. Though argued to improve physical performance by reducing serotonin function, such effects are generally considered modest at best. However, BCAA ingestion also lowers tyrosine uptake, and dopamine synthesis in brain. Increasing dopamine function in brain improves performance, suggesting that BCAA may fail to increase performance because dopamine is reduced. Conceivably, BCAA administered with tyrosine could prevent the decline in dopamine, while still eliciting a drop in serotonin. Such an LNAA mixture might thus prove an effective enhancer of physical performance. The thoughtful development and application of dietary proteins and LNAA mixtures may thus produce treatments with predictable and useful functional effects.

This paper discusses the application of a reagentless, selective microbiosensor as a useful alternative tool for monitoring D-serine in neural samples. The main components of the 125-μm-diameter disk biosensor were D-amino acid oxidase for D-serine sensitivity (linear region slope, 61 ± 7 μA cm(-2) mM(-1); limit of detection, 20 nM), and poly-phenylenediamine for rejection of electroactive interference. The response time of the biosensor was of the order of 1 s, ideal for 'real-time' monitoring, and detection of systemically administered D-serine in brain extracellular fluid is demonstrated. Exploitation of this probe might resolve queries involving regulation of D-serine in excitotoxicity, and modulation of N-methyl-D-aspartate receptor function by D-serine and glycine in the central nervous system.

Targeting mechanisms that result in increased concentrations of kynurenic acid (KYNA) in the brain has been considered as a therapeutic approach for the treatment of epilepsy and certain neurodegenerative disorders. Recently, KYNA has been implicated in the effects produced by the high-fat and low-protein/carbohydrate ketogenic diet (KD) in a report demonstrating an increased production of KYNA in vitro by one of the ketone bodies, β-hydroxybutyrate, elevated by the KD. To further explore this association, brain concentrations of KYNA were compared in young (3 weeks old) and adult (8-10 weeks old) rats that were chronically exposed to the KD and regular diet. Exposure to the KD resulted in the anticipated elevations of β-hydroxybutyrate with accompanying decreases in glucose concentrations. In comparison to rats fed the regular diet, KYNA concentrations were significantly (p < 0.05) increased in the hippocampus (256 and 363% increase in young and adult rats, respectively) and in the striatum (381 and 191% increase in young and adult rats, respectively) in KD-fed rats. KD-induced increases in KYNA concentrations in young versus adult rats in the hippocampus and striatum were comparable (p > 0.05). Exposure to the KD had no effect on KYNA concentrations in the cortex of young and adult rats (p > 0.05). In summary, chronic exposure to the KD resulted in several-fold increases in KYNA concentrations in discrete brain structures in the rats. Thus, the relevant clinical question for further exploration is whether KD-induced increases in KYNA concentrations can translate into clinically significant improvements in neuropsychiatric diseases associated with KYNA hypofunction.

Schizophrenia is a debilitating mental disorder with a global prevalence of 1% and its etiology remains poorly understood. In the current study we investigated the influence of antipsychotic drugs on the effects of MK-801 administration, which is a drug that mimics biochemical changes observed in schizophrenia, on Na(+), K(+)-ATPase activity and some parameters of oxidative stress in zebrafish brain. Our results showed that MK-801 treatment significantly decreased Na(+), K(+)-ATPase activity, and all antipsychotics tested prevented such effects. Acute MK-801 treatment did not alter reactive oxygen/nitrogen species by 2'7'-dichlorofluorscein (H2DCF) oxidation assay, but increased the levels of thiobarbituric acid reactive substances (TBARS), when compared with controls. Some antipsychotics such as sulpiride, olanzapine, and haloperidol prevented the increase of TBARS caused by MK-801. These findings indicate oxidative damage might be a mechanism involved in the decrease of Na(+), K(+)-ATPase activity induced by MK-801. The parameters evaluated in this study had not yet been tested in this animal model using the MK-801, suggesting that zebrafish is an animal model that can contribute for providing information on potential treatments and disease characteristics.

Several lines of evidence indicate that excess iron may play an etiologically significant role in neurodegenerative disorders. This idea is supported, for example, by experimental studies in animals demonstrating significant neuroprotection by iron chelation. Here, we tested whether this effect might be related to a functional link between iron and the endogenous excitotoxin quinolinic acid (QUIN), a presumed pathogen in several neurological disorders. In particular, the present in vitro study was designed to examine the effects of Fe(2+), a known co-factor of oxygenases, on the activity of QUIN's immediate biosynthetic enzyme, 3-hydroxyanthranilic acid dioxygenase (3HAO), in the brain. In crude tissue homogenate, addition of Fe(2+) (2-40 μM) stimulated 3HAO activity 4- to 6-fold in all three species tested (mouse, rat and human). The slope of the iron curve was steepest in rat brain where an increase from 6 to 14 μM resulted in a more than fivefold higher enzyme activity. In all species, the Fe(2+)-induced increase in 3HAO activity was dose-dependently attenuated by the addition of ferritin, the main iron storage protein in the brain. The effect of iron was also readily prevented by N,N'-bis(2-hydroxybenzyl) ethylenediamine-N,N'-diacetic acid (HBED), a synthetic iron chelator with neuroprotective properties in vivo. All these effects were reproduced using neostriatal tissue obtained postmortem from normal individuals and patients with end-stage Huntington's disease. Our results suggest that QUIN levels and function in the mammalian brain might be tightly controlled by endogenous iron and proteins that regulate the bioavailability of iron.

The locomotor effects of (-)- and (+)-OSU6162 were evaluated in 'low activity' animals (reserpinized mice and habituated rats) and 'high activity' animals (drug-naive mice and non-habituated rats). Both enantiomers of OSU6162 had dual effects on behavior, stimulating locomotor activity in 'low activity' animals and inhibiting locomotor activity in 'high activity' animals. There were also certain differences between the two enantiomers in their behavioral profiles. The stimulatory effects of both enantiomers in reserpinized mice were blocked by the 5-HT2A selective antagonist M100907, but not by the D2-selective antagonists haloperidol or raclopride, or by the D1-selective antagonists SCH23390 or SCH39166. The stimulatory effect in mice was more pronounced for (+)- than for (-)-OSU6162. In drug-naive mice, both enantiomers of OSU6162 produced head twitches, albeit to a much lesser extent than DOI, and both enantiomers inhibited DOI-induced head twitches, the (-)-form more effectively so than the (+)-form. These results suggest that (-)- and (+)-OSU6162 are partial agonists on 5-HT2A receptors and that the (+)-form has a higher intrinsic activity than the (-)-form. At high doses, both enantiomers inhibited locomotor activity in drug-naive mice, with (-)-OSU6162 being more potent than (+)-OSU6162. Similarly, in high-active rats, both enantiomers inhibited locomotor activity, with the (-)-enantiomer being more potent than the (+)-enantiomer. Conversely, in habituated rats, both enantiomers stimulated locomotor activity, and here, as opposed to the case in low-active mice, (-)-OSU6162 was more effective than (+)-OSU6162. The stimulatory effects in habituated rats of both enantiomers could be antagonized with either haloperidol or M100907. Overall, these results indicate that the dual effects on behavior of (-)- and (+)-OSU6162 are mediated through D2 and 5-HT2A receptors, consistent with their in vitro functional selectivity profiles (see Burstein et al., accompanying paper). Thus, both enantiomers of OSU6162 seem to act as stabilizers not only on dopaminergic, but also on serotonergic brain signaling. These discoveries have important implications for the potential clinical utility of both compounds, as well as for several of their congeners.

Synaptic pathology and disturbed glutamatergic neurotransmission contribute to the neurobiology of depression. Reduced expression of glutamate transporters, most importantly excitatory amino acid transporter (EAAT2), was reported in human studies and animal models. We therefore assessed the effects of antidepressant treatment upon EAAT2 expression. Male Sprague-Dawley rats received daily intraperitoneal injections of the antidepressants desipramine (DES, N = 7), fluoxetine (FLU, N = 7), tranylcypromine (TRAN, N = 5) or a saline control (CON, N = 5) for a period of 14 days. The expression of the major glial glutamate transporter EAAT2 was evaluated by semi-quantitative in situ hybridizations using a (35)S-labeled cRNA probe. Treatment with FLU significantly induced EAAT2 expression in hippocampal and cortical regions in comparison with saline injections, while DES and TRAN-applications did not exert significant effects. It can be postulated that increased expression of EAAT2 may counterbalance the tonus of glutamatergic neurotransmission. Our findings are in concert with human post-mortem findings, valid animal models of depression, antidepressive effects of NMDA-antagonists, and the glutamatergic theory of depression. Further studies should examine the effects of antidepressant treatments upon EAAT2 expression in rodent models of depression to further elucidate the underlying molecular mechanisms.

The presence of the blood-brain barrier (BBB) makes extremely difficult to develop efficacious strategies for targeting contrast agents and delivering drugs inside the Central Nervous System (CNS). To overcome this drawback, several kinds of CNS-targeted nanoparticles (NPs) have been developed. In particular, we proposed poly-lactide-co-glycolide (PLGA) NPs engineered with a simil-opioid glycopeptide (g7), which have already proved to be a promising tool for achieving a successful brain targeting after i.v. administration in rats. In order to obtain CNS-targeted NPs to use for in vivo imaging, we synthesized and administrated in mice PLGA NPs with double coverage: near-infrared (NIR) probe (DY-675) and g7. The optical imaging clearly showed a brain localization of these novel NPs. Thus, a novel kind of NIR-labeled NPs were obtained, providing a new, in vivo detectable nanotechnology tool. Besides, the confocal and fluorescence microscopy evidences allowed to further confirm the ability of g7 to promote not only the rat, but also the mouse BBB crossing.

In the present study, light and electron microscopy were used to examine heat shock protein (HSP 72 kD) expression during acute methamphetamine (METH) intoxication in rats and evaluate its relationships with brain temperature and alterations in a number of other histochemical and morphological parameters. Freely moving rats received METH at the same dose (9 mg/kg, sc) but at different ambient temperatures (23 and 29°C), showing a wide range of brain temperature elevations (37.6-42.5°C); brains were taken for histochemical and morphological evaluations at peak of brain temperature increase. We found that acute METH intoxication induces massive and wide-spread HSP expression in neural and glial cells examined in detail in the cortex, hippocampus, thalamus, and hypothalamus. In each of these structures, the number of HSP-positive cells tightly correlated with brain temperature elevation. The changes in HSP immunoreactivity were also tightly related to alterations in permeability of the blood-brain barrier, acute glial activation, and brain edema assessed by albumin and GFAP immunoreactivity and measuring tissue water content, respectively. While robust and generalized HSP production normally appears to be the part of an adaptive brain response associated with METH-induced metabolic activation, activation of this protective mechanism has its natural limits and could not counteract the damaging effects of oxidative stress, high temperature, and edema--the leading factors of METH-induced neurotoxicity.

This article highlights some landmarks in the history of levodopa, beginning with its isolation in 1910-13 from seedlings of Vicia faba to the demonstration, in 1961, of its "miraculous" effect in patients with Parkinson's disease (PD). Midway between these two time points, in 1938, L: -dopa decarboxylase was discovered, the enzyme that produces dopamine (DA) from levodopa. In 1957, DA was shown to occur in the brain, and in 1959 it was found to be enriched in the basal ganglia. At that time the striatal localization of DA, together with studies done in 1957-58 in naive and reserpine-treated animals regarding DA in the brain and the central effects of levodopa, suggested its possible involvement in "extrapyramidal control" and "reserpine parkinsonism". Following these discoveries, a study of (postmortem) brains of patients with basal ganglia disorders, including PD, was started, demonstrating, in 1960, a severe striatal DA deficit specifically in PD, thus furnishing a rational basis for the concept of "DA replacement therapy" with levodopa. Accordingly, in 1961, the first highly successful clinical trial with i.v. levodopa was carried out. In 1963, the DA deficit in the PD substantia nigra was found, indicative of a nigrostriatal DA pathway in the human brain, subsequently established in animal studies in 1964-65. In 1967, the chronic, high dose oral levodopa regimen was introduced in treatment of PD. Besides the above highlights in the history of levodopa, the article also cites critical opinions of world authorities in brain research of the time, harmful to the cause of DA, levodopa and PD. Today, the concept of DA replacement with levodopa is uncontested, with levodopa being the "gold standard" of modern drug treatment of PD.

The purpose of the present study was to determine whether repeated treatment with the D2 partial agonist aripiprazole or the D2 antagonist haloperidol alters dopamine (DA) synthesis characteristics in the dorsal striatum of young rats. To this end, rats received a daily pretreatment regimen of aripiprazole or haloperidol on postnatal days (PD) 10-20 and were tested 24 or 72 h later after an acute injection of vehicle, aripiprazole, haloperidol, or quinpirole (a D2 agonist). For comparison purposes, adult rats were pretreated with an 11-day regimen of saline or haloperidol on PD 70-80 and DA synthesis was measured after acute drug treatment on PD 83. Dorsal striatal DA synthesis was determined by measuring L-dihydroxyphenylalanine accumulation after NSD-1015 treatment. In a separate experiment, the ability of repeated drug treatment to up-regulate dorsal striatal D2 receptors was assessed in young and adult rats 72 h after drug discontinuation. The major findings of this study were that: (a) acute treatment with haloperidol and aripiprazole increased DA synthesis while quinpirole reduced it; (b) pretreatment with haloperidol and aripiprazole blunted the synthesis-modulating effects of acutely administered dopaminergic drugs; and (c) DA synthesis of young and adult rats was affected in a qualitatively similar manner by DA agonist, antagonist, and partial agonist drugs. In conclusion, results from the present study suggest that synthesis-modulating autoreceptors in the dorsal striatum are functionally mature by the end of the preweanling period and DA synthesis declines to near basal levels during the course of repeated aripiprazole treatment.

A decrease in cerebral glucose metabolic uptake is an early and characteristic sign of Alzheimer's disease (AD). Streptozotocin (STZ) is a bacterial toxin which damages insulin-producing cells and insulin receptors. Intracerebroventricular (icv) application of STZ in rats has been found to chronically decrease cerebral glucose uptake and produce other effects that bear a resemblance to several other molecular and pathological features of AD. In the present experiments in vivo (1)H MR Spectroscopy with short echo time (3 ms) was used to non-invasively obtain a neurochemical profile of rat brains, 3 weeks and 2 months after double icv injections of STZ or vehicle. Seventeen metabolites were quantified from 27 microL tissue volume which included hippocampus and a part of cerebral cortex, using the LCModel and unsuppressed water signal as an internal reference. Three weeks after icv STZ several metabolites were significantly decreased, the most prominent changes noted in glycerophosphocholine and phosphocholine (-38 +/- 5%), glutathione (-37 +/- 4%), taurine (-30 +/- 19%), glutamate (-26 +/- 14%), phosphocreatine (-23 +/- 15%) and N-acetylaspartate (-16 +/- 6%). On the contrary, the concentration of N-acetylaspartylglutamate was found significantly increased (+38 +/- 18%). After 2 months some of these changes were even more pronounced. We conclude that in vivo (1)H MRS of rat brain following icv STZ injections provides a new input into a better understanding of the critical dependency of neural function and structure on brain glucose consumption, and may be of relevance in further studies of AD pathomechanism.

Lithium, which is approved for treating patients with bipolar disorder, is reported to inhibit 3'(2')-phosphoadenosine-5'-phosphate (PAP) phosphatase activity. In yeast, deletion of PAP phosphatase results in elevated PAP levels and in inhibition of sulfation and of growth. The effect of lithium on PAP phosphatase is remarkable for the low Ki (approximately 0.2 mM), suggesting that this system would be almost completely shut down in vivo with therapeutic levels of 1 mM lithium, thereby elevating PAP levels. To test the hypothesis that lithium inhibition of PAP phosphatase is pharmacologically relevant to bipolar disorder, we fed rats LiCl for 6 weeks, and assayed brain PAP levels after subjecting the brain to high-energy microwaving. We also measured PAP phosphatase mRNA and protein levels in frozen brain tissue of lithium-treated mice. Brain adenosine phosphates were extracted by trichloroacetic acid and assayed by HPLC with a gradient system of two phases. PAP phosphatase mRNA was measured by RT-PCR, and PAP phosphatase protein was measured by Western blotting. Brain PAP levels were below detection limit of 2 nmol/g wet weight, even following lithium treatment. Lithium treatment also did not significantly change brain PAP phosphatase mRNA or protein levels. These results question the relevance of PAP phosphatase to the therapeutic mechanism of lithium. A statistically significant 25% reduced brain ADP/ATP ratio was found following lithium treatment in line with lithium's suggested neuroprotective effects.

Negative symptoms in schizophrenia respond poorly to antipsychotics, but may improve when these are augmented with selective serotonin reuptake inhibitors (SSRIs). The molecular mechanisms underlying the augmentation are unclear. Nevertheless, significant progress has been made, pointing to some candidate systems which may be involved in SSRI-antipsychotic synergism. Thus, the enhanced dopamine release by SSRI-antipsychotic treatment is modulated by specific serotonergic receptors and by tyrosine hydroxylase. There are modifications in gamma-aminobutyric acid system via glutamate decarboxylase 67, protein kinase C beta and the receptor for activated C-kinase 1 (Rack1). Some studies indicate the input of transcription and neurotrophic factors as phospho-cyclic adenosine monophosphate response element-binding protein, Fos and fibroblast growth factor-2. Alterations in calcium signaling (neurogranin, regulator of G-protein signaling and Rack1) and in cytokine receptors for interleukin-8 and chemokine have also been reported. While as yet limited in scope, the evidence suggests definable molecular targets which may be implicated in drug development based on SSRI-antipsychotic synergistic actions.

Rationale and Objectives: We previously showed that systemic administration of the prototypical alpha-2 noradrenaline (NA) receptor antagonist yohimbine increases alcohol self-administration and reinstatement. Yohimbine also acts as an agonist of 5-hydroxytryptamine (5-HT) 5-HT1A receptors, which have been shown to be involved in alcohol seeking. Here, we determined the contributions of the alpha-2 and 5-HT1A properties of yohimbine to its effects on alcohol seeking., Methods: The effects of lesions of the dorsal or ventral NA bundles with 6-OHDA on yohimbine-induced alcohol self-administration were first determined in male Wistar rats trained to self-administer alcohol (12% w/v, 0.19 ml per alcohol delivery), and then on reinstatement induced by yohimbine after extinction of the operant response. It was then determined whether the selective alpha-2 antagonist RS-79948 (0.1, 0.2, 0.4 mg/kg) would mimic the effects of yohimbine on self-administration and reinstatement. The effects of the alpha-2 receptor agonist clonidine, or the 5-HT1A antagonist WAY 100,635 were then determined on yohimbine-induced self-administration and reinstatement., Results: Lesions of the NA systems did not affect yohimbine-induced alcohol self-administration or reinstatement, and RS-79948 did not mimic the effects of yohimbine. Clonidine did not significantly affect increased alcohol self-administration induced by yohimbine, but did attenuate its effects on reinstatement. Blockade of 5-HT1A receptors reduced both yohimbine-induced self-administration and reinstatement., Conclusions: These results suggest that alpha-2 antagonist properties of yohimbine may play a role in the reinstatement of alcohol-seeking, but not self-administration. On the other hand, yohimbine's actions on 5-HT1A receptors contribute to its effects on both alcohol self-administration and reinstatement.

Rationale: Repeated exposure to cocaine progressively increases drug-induced locomotor activity, which is termed behavioral sensitization. Enhanced excitatory output from the medial prefrontal cortex (mPFC), which can be modulated by group II metabotropic glutamate receptors (mGluR), is thought to play a key role in the development of sensitization to cocaine., Objectives: The present studies were designed to determine whether the ability of intra-mPFC injections of the group II mGluR agonist 2R,4R-4-aminopyrrolidine-2,4-dicarboxylate (APDC) to inhibit cocaine-induced motor activity and dopamine release in the nucleus accumbens is reduced in sensitized animals., Results: Initial studies demonstrated that injection of APDC (0.015-15 nmol/side) into the mPFC dose dependently reduced cocaine-induced (15 mg/kg, i.p.) motor activity. The lowest dose in the present studies that significantly reduced the acute motor-stimulant response to cocaine was 1.5 nmol/side. The specificity of the effects of APDC was confirmed by demonstrating that intra-mPFC co-injection of LY341495 (1.5 nmol/side), a group II mGluR antagonist, prevented the inhibitory actions of APDC. Finally, it was shown that intra-mPFC injection of APDC was able to prevent the initiation of behavioral and neurochemical sensitization to cocaine. Intra-mPFC APDC was also observed to block the expression of cocaine-induced sensitization after short (1 day), but not prolonged (7 and 30 days), abstinence from cocaine., Conclusions: Taken together, these data suggest that mPFC group II mGluR function is reduced following extended abstinence from repeated cocaine.

Rationale: Interval timing in the free-operant psychophysical procedure is sensitive to the monoamine-releasing agent d-amphetamine, the D(2)-like dopamine receptor agonist quinpirole, and the D(1)-like agonist 6-chloro-2,3,4,5-tetrahydro-1-phenyl-1H-3-benzepine (SKF-81297). The effect of d-amphetamine can be antagonized by selective D(1)-like and 5-HT(2A) receptor antagonists. It is not known whether d-amphetamine's effect requires an intact 5-hydroxytryptamine (5-HT) pathway., Objective: The objective of this study was to examine the effects of d-amphetamine, quinpirole, and SKF-81297 on timing in intact rats and rats whose 5-hydroxytryptaminergic (5-HTergic) pathways had been ablated., Materials and Methods: Rats were trained under the free-operant psychophysical procedure to press levers A and B in 50-s trials in which reinforcement was provided intermittently for responding on A in the first half, and B in the second half of the trial. Percent responding on B (%B) was recorded in successive 5-s epochs of the trials; logistic functions were fitted to the data for derivation of timing indices (T(50), time corresponding to %B = 50%; Weber fraction). The effects of d-amphetamine (0.4 mg kg(-1) i.p.), quinpirole (0.08 mg kg(-1) i.p.), and SKF-81297 (0.4 mg kg(-1) s.c.) were compared between intact rats and rats whose 5-HTergic pathways had been destroyed by intra-raphe injection of 5,7-dihydroxytryptamine., Results: Quinpirole and SKF-81297 reduced T(50) in both groups; d-amphetamine reduced T(50) only in the sham-lesioned group. The lesion reduced 5-HT levels by 80%; catecholamine levels were not affected., Conclusions: d-Amphetamine's effect on performance in the free-operant psychophysical procedure requires an intact 5-HTergic system. 5-HT, possibly acting at 5-HT(2A) receptors, may play a 'permissive' role in dopamine release.

Rationale: Research on methamphetamine (MA) toxicity primarily focuses on the possibility that some of the behavioural problems in human MA users might be caused by damage to brain dopamine neurones. However, animal data also indicate that MA can damage brain serotonin neurones, and it has been suggested that cognitive problems and aggression in MA users might be explained by serotonergic damage. As information on the brain serotonin system in human MA users is fragmentary, our objective was to determine whether protein levels of serotonin transporter (SERT), a key marker of serotonin neurones, are decreased in brain of chronic MA users., Methods: SERT immunoreactivity was measured using an immunoblotting procedure in autopsied brain of 16 chronic MA users testing positive for the drug in blood and brain and matched controls., Results: SERT levels were non-significantly decreased (-14% to -33%) in caudate, putamen and thalamus (normal in hippocampus), and, unlike the robust striatal dopamine reduction, there was marked overlap between control and MA user ranges. Concentrations of SERT were significantly decreased (-23% to -39%) in orbitofrontal and occipital cortices (normal in frontopolar and temporal cortices)., Conclusions: Our data suggest that MA might modestly damage brain serotonin neurones and/or inhibit SERT protein expression, with cerebral cortex being more affected than sub-cortical regions. The SERT reduction in orbitofrontal cortex complements other data suggesting involvement of this area in MA-related behaviour. Decreased brain SERT could also be related to the clinical finding that treatment with a selective serotonin re-uptake inhibitor might increase relapse to MA.

Rationale: The behavioral effects of nicotine and the role of the beta2-containing nicotinic receptors in these behaviors are well documented. However, the behaviors altered by nicotine rely on the functioning on multiple brain circuits where the high-affinity beta2-containing nicotinic receptors (beta2*nAChRs) are located., Objectives: We intend to see which brain circuits are activated when nicotine is given in animals naïve for nicotine and whether the beta2*nAChRs are needed for its activation of the blood oxygen level dependent (BOLD) signal in all brain areas., Materials and Methods: We used functional magnetic resonance imaging (fMRI) to measure the brain activation evoked by nicotine (1 mg/kg delivered at a slow rate for 45 min) in anesthetized C57BL/6J mice and beta2 knockout (KO) mice., Results: Acute nicotine injection results in a significant increased activation in anterior frontal, motor, and somatosensory cortices and in the ventral tegmental area and the substantia nigra. Anesthetized mice receiving no nicotine injection exhibited a major decreased activation in all cortical and subcortical structures, likely due to prolonged anesthesia. At a global level, beta2 KO mice were not rescued from the globally declining BOLD signal. However, nicotine still activated regions of a meso-cortico-limbic circuit likely via alpha7 nicotinic receptors., Conclusions: Acute nicotine exposure compensates for the drop in brain activation due to anesthesia through the meso-cortico-limbic network via the action of nicotine on beta2*nAChRs. The developed fMRI method is suitable for comparing responses in wild-type and mutant mice.

Rationale: Nicotine improves cognitive function in a number of animal models including rats, mice, monkeys, and recently, zebrafish. The zebrafish model allows higher throughput and ease in discovering mechanisms of cognitive improvement., Materials and Methods: To further characterize the neural bases of nicotine effects on learning in zebrafish, we determined changes in dopaminergic systems that accompany nicotine-enhanced learning., Results: Nicotine improved learning and increased brain levels of dihydroxyphenylacetic acid (DOPAC), the primary dopamine metabolite. There was a significant correlation between choice accuracy and DOPAC levels. The nicotinic antagonist mecamylamine blocked the nicotine-induced increase in DOPAC concentrations, in line with our previous finding that mecamylamine reversed nicotine-induced learning improvement., Conclusions: Dopamine systems are related to learning in zebrafish; nicotine exposure increases both learning rates and DOPAC levels; and nicotinic antagonist administration blocks nicotine-induced rises in DOPAC concentrations. Rapid cognitive assessment of drugs with zebrafish could serve as a useful screening tool for the development of new therapeutics for cognitive dysfunction.

Rationale: Development of cognitive-enhancing drugs that delay or halt mild cognitive impairment progression to Alzheimer's disease would be of great benefit., Objectives: The aim of this study was to examine the ability of (S)-2,3-dihydro-[3,4]-cyclopentano-1,2,4-benzothiadiazine-1,1-dioxide (S 18986), a positive allosteric modulator of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, to improve behavioral performance and alleviate age-related deficits in oxidative stress status in the prelimbic cortex and hippocampus., Materials and Methods: Daily administration of S 18986 (0.1, 0.3, and 1.0 mg/kg) or vehicle was given to separate groups of male rats starting at 12 months of age. Additionally, daily vehicle administration was given to a group of rats starting at 3 months of age. Four months after initiation of drug administration, rats were trained and tested in an operant-delayed alternation task and a reinforcer devaluation task. Upon completion of testing, oxidative stress status was assessed in the prelimbic cortex and hippocampus., Results: S 18986 dose-dependently altered responses in the reinforcer devaluation task such that aged rats came to resemble young rats. There were no age or drug effects in the operant-delayed alternation task. Levels of the lipid peroxidation product 4-hydroxy-nonenal (HNE) were increased, and Cu/Zn-superoxide dismutase (SOD) levels were decreased in prelimbic cortex in aged rats, changes that were reversed by S 18986. Similarly, age-related increases in hippocampal HNE levels were prevented by S 18986., Conclusions: Positive modulation of AMPA receptor activity may be a therapeutic approach to halt or slow progression of mild cognitive impairment via improvement in oxidative stress status in the hippocampus and prelimbic cortex.

Rationale: Selective 5-ht(6) receptor antagonists like Ro 04-6790 prolong memory in many rodent preclinical paradigms, possibly by blocking tonic 5-HT-evoked GABA release and allowing disinhibition of cortico-limbic glutamatergic and cholinergic neurones. If this is the case, behavioural responses to Ro 04-6790 should be abolished by depletion of endogenous 5-HT, and selective lesions of dorsal raphé (DR) or median raphé (MR) 5-HT pathways would allow the neuroanatomical substrates underlying the cognitive effects of 5-ht(6) receptor antagonists to be elucidated., Objectives: This study compared the effect of Ro 04-6790 on novel object discrimination (NOD) before and after sham or 5,7-dihydroxytryptamine (5,7-DHT)-induced lesions produced by injection into the lateral ventricles (LV), DR or MR., Materials and Methods: NOD tests used a 4 h inter-trial interval (ITI) and Ro 04-6790 (10 mg kg(-1) i.p.) was administered 20 min before the familiarization trial. Brain region-specific 5-HT depletion was assessed by high performance liquid chromatography with electrochemical detection (HPLC-ED)., Results: Widespread LV or selective MR, but not DR lesions, abolished the ability of Ro 04-6790 to delay natural forgetting. Successful performance of all lesioned rats in subsequent 'drug-free' NOD tests using a 1 h ITI excluded the possibility of any confounding effects on visual acuity or motivation., Conclusions: The ability of Ro 04-6790 to prolong object recognition memory requires blockade of MR 5-HT function. Because DR lesions did not produce the expected depletion of striatal 5-HT an additional contribution of DR inputs to this region cannot be completely excluded.

Rationale: Performance of cognitive tasks in nonhuman primates (NHPs) requires specific brain regions to make decisions under different degrees of difficulty or "cognitive load.", Objective: Local cerebral metabolic activity ([18F]FDG PET imaging) in dorsolateral prefrontal cortex (DLPFC), medial temporal lobe (MTL), and dorsal striatum (DStr) is examined in NHPs performing a delayed-match-to-sample (DMS) task with variable degrees of cognitive load., Materials and Methods: Correlations between cognitive load and degree of brain metabolic activity were obtained with respect to the influence of the ampakine CX717 (Cortex Pharmaceuticals), using brain imaging and recordings of neuronal activity in NHPs and measures of intracellular calcium release in rat hippocampal slices., Results: Activation of DLPFC, MTL, and DStr reflected changes in performance related to cognitive load within the DMS task and were engaged primarily on high load trials. Similar increased activation patterns and improved performance were also observed following administration of CX717. Sleep deprivation in NHPs produced impaired performance and reductions in brain activation which was reversed by CX717. One potential basis for this facilitation of cognition by CX717 was increased firing of task-specific hippocampal cells. Synaptic mechanisms affected by CX717 were examined in rat hippocampal slices which showed that N-methyl-D-aspartic acid-mediated release of intracellular calcium was reduced in slices from sleep-deprived rats and reversed by application of CX717 to the bathing medium., Conclusions: The findings provide insight into how cognition is enhanced by CX717 in terms of brain, and underlying neural, processes that are activated on high vs. low cognitive load trials.

Rationale: Serotonin transporter (SERT) knockout (-/-) mice have an altered phenotype in adulthood, including high baseline anxiety and depressive-like behaviors, associated with increased baseline extracellular serotonin levels throughout life., Objectives: To examine the effects of increases in serotonin following the administration of the serotonin precursor 5-hydroxy-L-tryptophan (5-HTP) in SERT wild-type (+/+), heterozygous (+/-), and -/- mice., Results: 5-HTP increased serotonin in all five brain areas examined with approximately 2- to 5-fold increases in SERT+/+ and +/- mice, and with greater 4.5- to 11.7-fold increases in SERT-/- mice. Behaviorally, 5-HTP induced exaggerated serotonin syndrome behaviors in SERT-/-, mice with similar effects in male and female mice. Studies suggest promiscuous serotonin uptake by the dopamine transporter (DAT) in SERT-/- mice, and here, the DAT blocker GBR 12909 enhanced 5-HTP-induced behaviors in SERT-/- mice. Physiologically, 5-HTP induced exaggerated temperature effects in SERT-deficient mice. The 5-HT1A antagonist WAY 100635 decreased 5-HTP-induced hypothermia in SERT+/+ and +/- mice with no effect in SERT-/- mice, whereas the 5-HT7 antagonist SB 269970 decreased this exaggerated response in SERT-/- mice only. WAY 100635 and SB 269970 together completely blocked 5-HTP-induced hypothermia in SERT+/- and -/- mice., Conclusions: These studies demonstrate that SERT-/- mice have exaggerated neurochemical, behavioral, and physiological responses to further increases in serotonin, and provide the first evidence of intact 5-HT7 receptor function in SERT-/- mice, with interesting interactions between 5-HT1A and 5-HT7 receptors. As roles for 5-HT7 receptors in anxiety and depression were recently established, the current findings have implications for understanding the high anxiety and depressive-like phenotype of SERT-deficient mice.

Rationale: Activation of the immune system typically occurs on a subchronic or chronic basis (e.g., in response to bacterial or viral insults). However, analyses of the effects of cytokine treatments have typically involved acute treatments, and limited data are available concerning the behavioral and central neurochemical impact of subchronic interleukin-1beta (IL-1beta) administration., Objectives: Several peripheral and central effects of IL-1beta treatment were assessed following single or repeated bolus injections or after infusion of the cytokine (through Alzet minipumps) over several days., Results: The impact of an acute bolus injection of IL-1beta (1.0 microg) on plasma corticosterone and on circulating IL-1beta, IL-6, and TNF-alpha were diminished following 5-day IL-1beta treatment, although high levels of sickness were still apparent. When IL-1beta (1.0 or 2.0 mug/day) was continuously infused over 3 days, plasma corticosterone and sickness were elevated, but these effects were attenuated after 7 days (subchronic) of treatment. As well, the effects of IL-1beta treatment on diurnal variations of motor activity diminished over days. Despite the diminution of the behavioral and neuroendocrine effects of the cytokine after treatment 7 days, subchronic IL-1beta infusion altered prefrontal cortical and hippocampal serotonin and norepinephrine utilization, and within these regions, the messenger RNA (mRNA) expression of IL-1beta, IL-6, TNF-alpha, and their receptors, as well as that of 5-HT(2C), 5-HT(1B) receptors, and p11, was increased., Discussion: The findings indicate that peripheral cytokine infusion markedly influences central cytokine mRNA expression and also influences 5-HT turnover, which might contribute to behavioral changes elicited by IL-1beta.

Rationale: l-Stepholidine, a dopamine D(2) antagonist with D(1) agonist activity, should in theory control psychosis and treat cognitive symptoms by enhancing cortical dopamine transmission. Though several articles describe its impact on the dopamine system, it has not been systematically evaluated and compared to available antipsychotics., Materials and Methods: We examined its in vitro interaction with dopamine D(2) and D(1) receptors and compared its in vivo pharmacokinetic profile to haloperidol (typical) and clozapine (atypical) in animal models predictive of antipsychotic activity., Results: In vitro, l-stepholidine showed significant activity on dopamine receptors, and in vivo, l-stepholidine demonstrated a dose-dependent striatal receptor occupancy (RO) at D(1) and D(2) receptors (D(1) 9-77%, 0.3-30 mg/kg; D(2) 44-94%, 1-30 mg/kg), though it showed a rather rapid decline of D(2) occupancy related to its quick elimination. In tests of antipsychotic efficacy, it was effective in reducing amphetamine- and phencyclidine-induced locomotion as well as conditioned avoidance response, whereas catalepsy and prolactin elevation, the main side effects, appeared only at high D(2)RO (>80%). This preferential therapeutic profile was supported by a preferential immediate early gene (Fos) induction in the nucleus accumbens over dorsolateral striatum. We confirmed its D(1) agonism in vitro, and then using D(2) receptor, knockout mice showed that l-stepholidine shows D(1) agonism in the therapeutic dose range., Conclusions: Thus, l-stepholidine shows efficacy like an "atypical" antipsychotic in traditional animal models predictive of antipsychotic activity and shows in vitro and in vivo D(1) agonism, and, if its rapid elimination does not limit its actions, it could provide a unique therapeutic approach to schizophrenia.

Rationale: A major clinical concern with the use of cannabinoid receptor 1 (CB1) direct agonists is that these compounds increase alcohol drinking and drug abuse-related behaviours. As an alternative approach, CB1-receptor-mediated activity can be facilitated by increasing anandamide levels with the use of hydrolase fatty acid amide hydrolase (FAAH) inhibitors., Objective: Using the selective FAAH inhibitor URB597, we investigated whether activation of the endogenous cannabinoid tone increases alcohol abuse liability, as what happens with the CB1 receptor direct agonists., Materials and Methods: URB597 was tested on alcohol self-administration in Wistar rats and on homecage alcohol drinking in genetically selected Marchigian Sardinian alcohol-preferring (msP) rats. In Wistar rats, URB597 effects on alcohol-induced anxiety and on stress-, yohimbine- and cue-induced reinstatement of alcohol seeking were also evaluated. For comparison, the effect of the CB1 receptor antagonist rimonabant on ethanol self-administration was also tested., Results: Under our experimental condition, intraperitoneal (IP) administration of URB597 (0.0, 0.3 and 1.0 mg/kg) neither increased voluntary homecage alcohol drinking in msP rats nor facilitated fixed ratio 1 and progressive ratio alcohol self-administration in nonselected Wistars. In the reinstatement tests, the compound did not have effects on cue-, footshock stress- and yohimbine-induced relapse. Conversely, URB597 completely abolished the anxiogenic response measured during withdrawal after an acute IP administration of alcohol (3.0 g/kg). Rimonabant (0.0, 0.3, 1.0 and 3.0 mg/kg) significantly reduced ethanol self-administration., Conclusions: Results demonstrate that activation of the endocannabinoid anandamide system by selective inhibition of FAAH does not increase alcohol abuse risks but does reduce anxiety associated to alcohol withdrawal. We thus can speculate that medication based on the use of endocannabinoid system modulators such as URB597 may offer important advantages compared to treatment with direct CB1 receptor activators.

Recently, we observed that central administration of L-arginine attenuated stress responses in neonatal chicks, but the contribution of nitric oxide (NO) to this response was minimal. The sedative and hypnotic effects of L-arginine may be due to L-arginine itself and/or its metabolites, excluding NO. To clarify the mechanism, the effect of intracerebroventricular (i.c.v.) injection of L-arginine metabolites on behavior under social separation stress was investigated. The i.c.v. injection of agmatine, a guanidino metabolite of L-arginine, had no effect during a 10 min behavioral test. In contrast, the i.c.v. injection of L-ornithine clearly attenuated the stress response in a dose-dependent manner, and induced sleep-like behavior. The L-ornithine concentration in the telencephalon and diencephalon increased following the i.c.v. injection of L-arginine. In addition, several free amino acids including L-alanine, glycine, L-proline and L-glutamic acid concentrations increased in the telencephalon. In conclusion, it appears that L-ornithine, produced by arginase from L-arginine in the brain, plays an important role in the sedative and hypnotic effects of L-arginine observed during a stress response. In addition, several other amino acids having a sedative effect might partly participate in the sedative and hypnotic effects of L-arginine.

Rationale: Antidepressant medications are effective only in a subpopulation of patients with depression, and some patients respond to certain drugs, but not others. The biological bases for these clinical observations remain unexplained., Objective: To investigate individual differences in response to antidepressants, we have examined the effects of the norepinephrine reuptake inhibitor desipramine (DMI) and the selective serotonin reutake inhibitor fluoxetine (FLU) in the forced swim test (FST) in rats that differ in their emotional behavior., Methods: As response to novelty correlates with numerous other measures of emotionality and substance abuse, we contrasted animals that are high responders (HR) in a novel environment with animals that are low responders (LR) and asked whether the two groups exhibit differential responses to DMI (10mg/kg) and FLU (20mg/kg)., Results: At the behavioral level, DMI caused a significant decrease in immobility in LR animals only, while FLU caused a significant reduction in immobility in both groups. Moreover, at the neural level, DMI treatment led to a decrease in FST-induced c-fos messenger RNA levels in medial prefrontal cortex (PFC) and paraventricular nucleus of the hypothalamus (PVN) in LR but not HR animals., Conclusions: Taken together, our results suggest that the HR-LR model is a useful tool to investigate individual differences in responses to norepinephrine reuptake inhibitors (NRIs) and that a differential activation of PFC and/or PVN could underlie some of the inter-individual differences in the efficacy of NRIs.

Rationale: Stimulants such as methamphetamine (METH) alter core temperature in a manner that is dependent on ambient temperature and that shows tolerance after chronic use. Our objectives were to (1) determine whether tolerance to METH-induced hyperthermia was a consequence of neurotoxicity to dopamine or serotonin and (2) determine the relationship between ambient temperature and chronic treatment on the METH-induced temperature response., Materials and Methods: Rats were treated with 1.0, 5.0, or 10.0 mg/kg METH at 24 degrees C (experiment 1) or treated with 5.0 mg/kg METH at 20 degrees C, 24 degrees C, or 28 degrees C (experiment 2). Treatment occurred for 12 days, and temperature measurements were made once per minute telemetrically during 7-h sessions in computer-regulated environments., Results: Peak increases in core temperature occurred at 60 min post-treatment for the 1.0 and 10.0 mg/kg doses, and at 180 min for the 5.0 mg/kg dose. Tolerance-like effects were seen with chronic 5.0 (mixed results) and 10.0 mg/kg METH in the absence of dopamine or serotonin depletions measured 2 weeks after the completion of treatment. After 5.0 mg/kg METH, variations in ambient temperature resulted in an early flexible change in core temperature (phase 1) (hyperthermia at 28 degrees and hypothermia at 20 degrees ) and a later inflexible hyperthermia (phase 2)., Conclusions: The results suggest that (1) the peak effect of different doses of METH occurs at different times (24 degrees ), (2) the diminished temperature response with chronic METH treatment was not associated with long-term dopamine and serotonin depletions, and (3) a two-phase temperature response to METH may reflect two independent mechanisms.

Rationale: Methamphetamine (METH) induces hyperthermia, which is diminished with chronic treatment in a dose-dependent manner. Our objective was to determine whether the temperature responses produced by a chronic, escalating-dose METH regimen and a chronic, 5.0 mg/kg dose regimen., Methods: Rats received pretreatment injections of saline, 5.0 mg/kg METH, 10.0 mg/kg METH (second comparison group), or an escalating-METH regimen (2-9 mg/kg) for 12 days. On day 13, all four groups were challenged with 10.0 mg/kg METH. Temperature measurements were made telemetrically at 24 degrees C ambient temperature., Results: Escalating pretreatment produced hyperthermia; with successive exposures, the hyperthermic peak shifted to the right. The 5.0-mg/kg-pretreatment group initially showed no change in temperature at 60 min post-treatment but developed hypothermia at 60 min with chronic treatment; at 3 h post-treatment, significant hyperthermia was present and did not diminish with chronic treatment. After the 10.0-mg/kg-METH challenge, the saline-pretreatment group was hyperthermic, and the 10.0-mg/kg-pretreatment group was hypothermic; the 5.0 mg/kg and escalating pretreatment groups were intermediate and were not different from each other. At 3 h post-challenge, no group differences were apparent. Dopamine (DA) and serotonin (5-HT) were not depleted when measured 2 weeks after treatment ended., Conclusions: (1) Escalating and 5.0-mg/kg regimens produced different temperature profiles during the 12-day pretreatment period but a similar diminished response to the 10.0-mg/kg-METH challenge on day 13. (2) The diminished temperature responses with chronic treatment occurred in the absence of long-term DA and 5-HT depletions.

Caffeic acid is a natural compound that inhibits 5-lipoxygenase (5-LOX). In mice, caffeic acid produces antidepressant-like effects and attenuates the decrease in cortical brain-derived neurotrophic factor (BDNF) mRNA induced by forced swimming. We used wild-type and 5-LOX-deficient mice and found that swimming reduced the cortical content of BDNF exon IV but not exon I mRNA. The BDNF transcript IV decrease was attenuated by caffeic acid in wild-type but not in 5-LOX-deficient mice, suggesting a role for 5-LOX in BDNF regulation.

L-arginine participates in many important and diverse biochemical reactions associated with the normal physiology of the organism. In the present study, we investigated the effect of central administration of L-arginine on the stress response and its mechanism in neonatal chicks. Intracerebroventricular (i.c.v.) injection of L-arginine clearly attenuated the stress response in a dose-dependent manner, and induced sleep-like behavior during 10 min. To clarify the mechanism by which L-arginine induces sedative and hypnotic effects in chicks, we investigated the effects of nitric oxide (NO) synthase (NOS) inhibitors on L-arginine-induced sedative and hypnotic effects, and as well as the effects of a NO donor. L-Arginine-induced (1.9 micromol) sedative and hypnotic effects were attenuated by i.c.v. co-injection with a non-selective NOS inhibitor N(G)-nitro-L-arginine methyl ester HCl (400 nmol). In addition, the effects of L-arginine were slightly attenuated by the inactive isomer of the NOS inhibitor N(G)-nitro-D-arginine methyl ester HCl (400 nmol). The i.c.v. injection of 3-morpholinosylnomine hydrochloride, a spontaneous NO donor, had little effect on postures. The i.c.v. injection of L-arginine had no effect on NOx concentration at various brain sites. These results suggested that the contribution of NO generation via NOS may be low in the sedative and hypnotic actions of L-arginine. Therefore, L-arginine and/or its metabolites, excluding NO, may be necessary for these actions.