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Developmental stress, including low socioeconomic status (SES), can induce dysregulation of the hypothalamic-pituitary-adrenal axis and result in long-term changes in stress reactivity. Children in lower SES conditions often experience more stress than those in other SES groups. There are multiple model systems of early environmental stress (EES), one of which is reduced cage bedding. Here we tested the effects of both prenatal and lactational EES in rats on a range of long-term behavioral and cognitive outcomes. There were persistent reductions in body weight in the EES rats in both sexes. The behavioral results showed no effects on learning and memory using tests of spatial learning or cognitive flexibility in the Morris water maze, egocentric learning in the Cincinnati water maze, or working memory in the radial-arm maze. There were no effects on basic open-field activity, elevated zero-maze, or forced swim test, but EES rats had reduced time in the dark side of the light/dark test. When rats were drug challenged in the open-field with d-amphetamine or MK-801, there were no differential responses to d-amphetamine, but the EES group under responded compared with the drug-induced hyperactivity in the control group in both males and females. The objective was to establish a developmental stress model that induced cognitive deficits and to the extent that this method did not cause such effects it was not the model we sought. However, the data showed several long-term effects of EES, including the reduced response to the irreversible NMDA antagonist MK-801. This effect merits further investigation., Competing Interests: Declaration of competing interest The authors declare no conflict of interest connected to this research., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Attention deficit hyperactivity disorder (ADHD) is a polygenic neurodevelopmental disorder that affects 8-12 % of children and >4 % of adults. Environmental factors are believed to interact with genetic predispositions to increase susceptibility to ADHD. No existing rodent model captures all aspects of ADHD, but several show promise. The main genetic models are the spontaneous hypertensive rat, dopamine transporter knock-out (KO) mice, dopamine receptor subtype KO mice, Snap-25 KO mice, guanylyl cyclase-c KO mice, and latrophilin-3 KO mice and rats. Environmental factors thought to contribute to ADHD include ethanol, nicotine, PCBs, lead (Pb), ionizing irradiation, 6-hydroxydopamine, neonatal hypoxia, some pesticides, and organic pollutants. Model validation criteria are outlined, and current genetic models evaluated against these criteria. Future research should explore induced multiple gene KOs given that ADHD is polygenic and epigenetic contributions. Furthermore, genetic models should be combined with environmental agents to test for interactions., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Deltamethrin (DLM) is a Type II pyrethroid pesticide widely used in agriculture, homes, public spaces, and medicine. Epidemiological studies report that increased pyrethroid exposure during development is associated with neurobehavioral disorders. This raises concern about the safety of these chemicals for children. Few animal studies have explored the long-term effects of developmental exposure to DLM on the brain. Here we review the CNS effects of pyrethroids, with emphasis on DLM. Current data on behavioral and cognitive effects after developmental exposure are emphasized. Although, the acute mechanisms of action of DLM are known, how these translate to long-term effects is only beginning to be understood. But existing data clearly show there are lasting effects on locomotor activity, acoustic startle, learning and memory, apoptosis, and dopamine in mice and rats after early exposure. The most consistent neurochemical findings are reductions in the dopamine transporter and the dopamine D1 receptor. The data show that DLM is developmentally neurotoxic but more research on its mechanisms of long-term effects is needed., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Developmental neurotoxicity (DNT) studies could benefit from revisions to study design, data analysis, and some behavioral test methods to enhance reproducibility. The Environmental Protection Agency (EPA) reviewed 69 studies submitted to the Office of Pesticide Programs. Two of the behavioral tests identified the lowest observable adverse effect level (LOAEL) 20 and 13 times, respectively, while the other two tests identified the LOAEL only 3 and 4 times, respectively. The EPA review showed that the functional observational battery (FOB) was least effective at detecting the LOAEL, whereas tests of learning and memory (L&M) had methodological shortcomings. Human neurodevelopmental toxicity studies over the past 30 years show that most of the adverse effects are on higher cognitive functions such as L&M. The results of human studies together with structure-function relationships from neuroscience, suggest that tests of working memory, spatial navigation/memory, and egocentric navigation/memory should be added to guideline studies. Collectively, the above suggest that EPA and EU DNT studies would better reflect human findings and be more relevant to children by aligning L&M tests to the same domains that are affected in children, removing less useful methods (FOB), and using newer statistical models to better account for random factors of litter and litter × sex. Common issues in study design and data analyses are discussed: sample size, random group assignment, blinding, elimination of subjective rating methods, avoiding confirmation bias, more complete reporting of species, housing, test protocols, age, test order, and litter effects. Litter in DNT studies should at least be included as a random factor in ANOVA models and may benefit from inclusion of litter × sex as random factors., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Latrophilin-3 (LPHN3), a G-protein-coupled receptor belonging to the adhesion subfamily, is a regulator of synaptic function and maintenance in brain regions that mediate locomotor activity, attention, and memory for location and path. Variants of LPHN3 are associated with increased risk for attention deficit hyperactivity disorder (ADHD) in some patients. Here we review the role of LPHN3 in the central nervous system (CNS). We describe synaptic localization of LPHN3, its trans-synaptic binding partners, links to neurodevelopmental disorders, animal models of Lphn3 disruption in different species, and evidence that LPHN3 is involved in cognition as well as activity and attention. The evidence shows that LPHN3 plays a more significant role in neuroplasticity than previously appreciated., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Two developmental stressors were compared in preweaning rats exposed to either one stressor or both. Stressors were barren cage rearing or maternal separation (pup isolation). 40 gravid Sprague-Dawley CD/IGS rats were randomly assigned to two cage conditions: standard (Std) cage or barren cage (Bar), 20 litters/condition throughout gestation and lactation. After delivery, litters were randomly culled to 4 males and 4 females. The second stressor was maternal separation: Two male/female pairs per litter were isolated from their dam 4 h/day (Iso) and two pairs were not (Norm). Hence, there were 4 conditions: Std-Norm, Std-Iso, Bar-Norm, and Bar-Iso. One pair/litter/stress condition received the following: elevated zero-maze (EZM), open-field, swim channel, Cincinnati water maze, conditioned fear, and open-field with methamphetamine challenge. The second pair/litter/condition received the light-dark test, swim channel, Morris water maze, forced swim, and EZM with diazepam challenge. Barren rearing reduced EZM time-in-open, whereas isolation rearing reduced open-field activity in males and increased it in females. Effects on straight channel swimming were minor. In the Cincinnati water maze test of egocentric learning, isolation rearing increased errors whereas barren cage housing reduced errors in combination with normal rearing. Barren cage with maternal separation (pup isolation) increased Cincinnati water maze escape latency but not errors. Barren cage housing reduced hyperactivity in response to methamphetamine. Isolation rearing increased time in open in the EZM after diazepam challenge. Trends were seen in the Morris water maze. These suggested that barren cage and isolation rearing in combination reduced latency on acquisition on days 1 and 2 in males, whereas females had increased latency on days 2 and 3. Combined exposure to two developmental stressors did not induce additive or synergistic effects, however the data show that these stressors had long-term effects with some evidence that the combination of both caused effects when either stressor alone did not, but synergism was not observed., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Response variability across the lifespan is an important consideration in toxicology and risk assessment, and the toxic effects of drugs and chemicals during adolescence need more research. This paper summarizes a workshop presented in March 2019, at the Society of Toxicology Annual Meeting in Baltimore, Maryland, that brought together experts in research on drug dependence and toxicity related to nicotine, cannabis, cocaine, and other illicit drugs during adolescence. The goal of the workshop was to address the following issues: (1) Do the effects of adolescent exposure differ from the same exposure in adults? (2) Are there unique biological markers of adolescent brain development? If so, what are they and how reliable are they? (3) Since multiple factors influence substance use disorder, can we disentangle risk factors for abuse and/or toxicity? What are the underlying biological susceptibilities that lead to dependence and neurotoxicity? What are the social, psychosocial and environmental factors that contribute to abuse susceptibilities? This paper reviews drug policy and national trends in adolescent substance use; the public health consequences of e-cigarettes; rat models of adolescent-onset nicotine self-administration and persisting effects of gestational nicotine; sex-dependent effects of delta-9-tetrahydrocannabinol on adolescent brain-behavior relationships; and translational approaches for identifying adolescent risk factors for transition to drug dependence. There is strong evidence that drug exposure prior to adulthood has longer lasting effects on behavior and the underlying neural circuitry. These effects, which are sex-dependent and influenced by stress, may be candidates as predictors of adolescent vulnerability. A major challenge to determining if adolescents have a unique susceptibility to dependence is whether and to what extent the human data allow distinction between the increased risk due to biological immaturity, an underlying biological susceptibility to dependence, or psychosocial and environmental factors for substance dependence. Factors important to consider for development of animal models include the timing and pattern of exposure as it relates to adolescence; age of assessment, and direct comparison with similar effects following exposures to adults to demonstrate that these effects are unique to adolescence. Here we provide a roadmap for further research into what makes adolescent brain development unique., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The importance of litter effects (clustering of variance among offspring in rodents) has been known for decades. The standard approach was to treat the entire litter as a unit or to select one male and one female from each litter to prevent oversampling. These methods work but are imperfect. Treating the litter as a whole fails to use valuable interindividual differences among offspring, and selecting representative pups fails to use all the data available. Golub and Sobin [https://doi.org/10.1016/j.ntt.2019.106841] address this using a better method. They show that using litter as a random factor in mixed linear models resolves this conundrum. As they demonstrate, such models control for litter clustering by partitioning litter variance from error variance. This reduces error variance and increases the power of F-tests of the independent variable(s). In our experience, this is the optimal solution. But as good as mixed linear models are when used with litter as a random factor, if other aspects of the experimental design are not appropriate, this cannot compensate for threats to validity from small sample sizes, dams not strictly randomly assigned to groups, repeated measure covariance structures not appropriately modeled, interactions not properly sliced, or a posteriori group comparisons not controlled for multiple comparisons. Appropriate handling of litter is only one consideration of experimental design and statistical analysis that when used in combination lead to valid, reproducible data., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Developmental stress, including low socioeconomic status (SES), can induce dysregulation of the hypothalamic-pituitary-adrenal axis and result in long-term changes in stress reactivity. Children in lower SES households experience more stress and are more likely to be exposed to environmental neurotoxins such as lead (Pb) and manganese (Mn) than children in higher SES households. Co-exposure to stress, Pb, and Mn during early development may increase the risk of central nervous system dysfunction compared with unexposed children. To investigate the potential interaction of these factors, Sprague-Dawley rats were bred, and litters born in-house were culled on postnatal day (P)1 to 6 males and 6 females. One male and female within each litter were assigned to one of the following groups: 0 (vehicle), 10 mg/kg Pb, 100 mg/kg Mn, or 10 mg/kg Pb + 100 mg/kg Mn (PbMn), water gavage, and handled only from P4-28 with half the litters reared in cages with standard bedding (29 litters) and half with no bedding (Barren; 27 litters). Mn and PbMn groups had decreased anxiety, reduced acoustic startle, initial open-field hypoactivity, increased activity following (+)-methamphetamine, deficits in egocentric learning in the Cincinnati water maze (CWM), and deficits in latent inhibition conditioning. Pb increased anxiety and reduced open-field activity. Barren-reared rats had decreased anxiety, CWM deficits, increased startle, and initial open-field hyperactivity. Mn, PbMn, Pb Barren-reared groups had impaired Morris water maze performance. Pb altered neostriatal serotonin and norepinephrine, Mn increased hippocampal serotonin in males, Mn + Barren-rearing increased neostriatal serotonin, and Barren-rearing decreased neostriatal dopamine in males. At the doses used here, most effects were in the Mn and PbMn groups. Few interactions between Mn, Pb, and rearing stress were found, indicating that the interaction of these three variables is not as impactful as hypothesized., (Copyright © 2018 Elsevier Inc. All rights reserved.)

This commentary is in response to the remarks of Drs. Christina Sobin, Mari Golub, and David Herr on the Special Issue of this Journal entitled "Assessment of Learning, Memory, and Attention in Developmental Neurotoxicology Regulatory Testing." I endorse the views expressed by Drs. Sobin, Golub, and Herr and add some discussion on a recent Organization for Economic Cooperation and Development (OECD) guideline, the Extended One Generation Reproductive Toxicology Guideline (OECD 446), in which testing for higher cognitive function (learning and memory) has been eliminated. The case against this decision is offered. It is noted that deficits in higher cognitive function are one of the hallmarks of human studies that find neurobehavioral toxicity in children after exposure to environmental agents such as lead, methylmercury, PCB, pesticides, and other environmental agents. It is noted that the OECD decision is at variance with the views of the scientific community in this field, including those of Drs. Sobin, Golub, and Herr. Why OECD took such action without the advice and consent of the field of developmental neurotoxicology is deeply concerning and potentially hazardous to children. I also endorse Dr. Herr's recommendation that in the future the Environmental Protection Agency negotiate study designs in advance with submitters as the Food and Drug Administration does to improve data quality for all neurobehavioral methods, and especially for tests of learning and memory that have not been adequately conducted in many past studies., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Manganese (Mn) is an essential element but neurotoxic at higher exposure levels. The effects of Mn overexposure (MnOE) on hippocampal and striatal-dependent learning and memory in rats were tested in combination with iron deficiency (FeD) and developmental stress that often co-occur with MnOE. Moderate FeD affects up to 15% of U.S. children and developmental stress is common in lower socio-economic areas where MnOE occurs. Pregnant Sprague-Dawley rats and their litters were housed in cages with or without (barren cage (BAR)) standard bedding from embryonic day (E)7 to postnatal day (P)28. Dams were fed a 90% FeD or iron sufficient (FeS) diet from E15-P28. Within each litter, separate offspring were treated with 100mg/kg Mn (MnOE) or vehicle (VEH) by gavage on alternate days from P4-28. Offspring were tested as adults in the Morris and Cincinnati water mazes. FeD and developmental stress interactively impaired spatial learning in the Morris water maze. Developmental stress and MnOE impaired learning and memory in both mazes. MnOE resulted in reduced CA1 hippocampal long-term potentiation (LTP) and increased levels of α-synuclein. Preweaning MnOE resulted in cognitive deficits on multiple domains of learning and memory accompanied by impaired LTP and α-synuclein changes, effects worsened by developmental stress., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Advantageous maneuvering through the environment to find food and avoid or escape danger is central to survival of most animal species. The ability to do so depends on learning and remembering different locations, especially home-base. This capacity is encoded in the brain by two systems: one using cues outside the organism (distal cues), allocentric navigation, and one using self-movement, internal cues (proximal cues), for egocentric navigation. Whereas allocentric navigation involves the hippocampus, entorhinal cortex, and surrounding structures, egocentric navigation involves the dorsal striatum and connected structures; in humans this system encodes routes and integrated paths and when over-learned, becomes procedural memory. Allocentric assessment methods have been extensively reviewed elsewhere. The purpose of this paper is to review one specific method for assessing egocentric, route-based navigation in rats: the Cincinnati water maze (CWM). The test is an asymmetric multiple-T maze arranged in such a way that rats must learn to find path openings along walls rather at ends in order to reach the goal. Failing to do this leads to cul-de-sacs and repeated errors. The task may be learned in the light or dark, but in the dark, wherein distal cues are eliminated, provides the best assessment of egocentric navigation. When used in conjunction with tests of other types of learning, such as allocentric navigation, the CWM provides a balanced approach to assessing the two major forms of navigational learning and memory found in mammals., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Manganese (Mn) is an essential element but neurotoxic at higher exposures, however, Mn exposure seldom occurs in isolation. It often co-occurs in populations with inadequate dietary iron (Fe) and limited resources that result in stress. Subclinical FeD affects up to 15% of U.S. children and exacerbates Mn toxicity by increasing Mn bioavailability. Therefore, we investigated Mn overexposure (MnOE) in rats in combination with Fe deficiency (FeD) and developmental stress, for which we used barren cage rearing. For barren cage rearing (BAR), rats were housed in cages with a wire grid floor or standard bedding material (STD) from embryonic day (E)7 through postnatal day (P)28. For FeD, dams were fed a 90% Fe-deficient NIH-07 diet from E15 through P28. Within each litter, different offspring were treated with 100mg/kg Mn (MnOE) or vehicle (VEH) by gavage every other day from P4-28. Behavior was assessed at two ages and consisted of: open-field, anxiety tests, acoustic startle response (ASR) with prepulse inhibition (PPI), sociability, sucrose preference, tapered beam crossing, and the Porsolt's forced swim test. MnOE had main effects of decreasing activity, ASR, social preference, and social novelty. BAR and FeD transiently modified MnOE effects. BAR groups weighed less and showed decreased anxiety in the elevated zero maze, had increased ASR and decreased PPI, and exhibited reduced sucrose preference compared with the STD groups. FeD animals also weighed less and had increased slips on the tapered beam. Most of the monoamine effects were dopaminergic and occurred in the MnOE groups. The results showed that Mn is a pervasive developmental neurotoxin, the effects of which are modulated by FeD and/or BAR cage rearing., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Cognitive tests of learning and memory (L&M) have been required by U.S. Environmental Protection Agency (EPA) developmental neurotoxicity test (DNT) guidelines for more than two decades. To evaluate the utility of these guidelines, the EPA reviewed 69 pesticide DNT studies. This review found that the DNT provided or could provide the point-of-departure for risk assessment by showing the Lowest Observable Adverse Effect Level (LOAEL) in 28 of these studies in relation to other reported end points. Among the behavioral tests, locomotor activity and auditory/acoustic startle provided the most LOAELs, and tests of cognitive function and the Functional Observational Battery (FOB) the fewest. Two issues arose from the review: (1) what is the relative utility of cognitive tests versus tests of unconditioned behavior, and (2) how might cognitive tests be improved? The EPA sponsored a symposium to address this. Bushnell reviewed studies in which both screening (locomotor activity, FOB, reflex ontogeny, etc.) and complex tests (those requiring training) were used within the same study; he found relatively little evidence that complex tests provided a LOAEL lower than screening tests (with exceptions). Levin reviewed reasons for including cognitive tests in regulatory studies and methods and evidence for the radial arm maze and its place in developmental neurotoxicity assessments. Driscoll and Strupp reviewed the value of serial reaction time operant methods for assessing executive function in developmental neurotoxicity studies. Vorhees and Williams reviewed the value of allocentric (spatial) and egocentric cognitive tests and presented methods for using the Morris water maze for spatial and the Cincinnati water maze for egocentric cognitive assessment. They also reviewed the possible use of water radial mazes. The relatively lower impact of cognitive tests in previous DNT studies in the face of the frequency of human complaints of chemical-induced cognitive dysfunction indicates that animal cognitive tests need improvement. The contributors to this symposium suggest that if the guidelines are updated, they be made more specific by recommending preferred tests and providing greater detail on key characteristics of such tests. Additionally, it is recommended that guidance be developed to address important issues with cognitive tests and to provide the information needed to improve the design, conduct, and interpretation of tests of higher function within a regulatory context. These steps will maximize the value of cognitive tests for use in hazard evaluation and risk assessment., (Copyright © 2015 Elsevier Inc. All rights reserved.)

There are a variety of chemicals, including pharmaceuticals, that alter neurobehavior following developmental exposure and guidelines for the conduct of studies to detect such effects by statute in the United States and Europe. Guidelines for Developmental Neurotoxicity Testing (DNT) studies issued by the U.S. Environmental Protection Agency (EPA) under prevailing law and European Organization for Economic Cooperation and Development (OECD) recommendations to member countries provide that such studies include a series of neurobehavioral and neuropathological assessments. Among these are assessment of cognitive function, specifically learning and memory. After reviewing 69 DNT studies submitted to the EPA, tests of learning and memory were noted to have detected the lowest observed adverse effect level (LOAELs) less frequently than behavioral tests of locomotor activity and acoustic/auditory startle, but slightly more than for the developmental Functional Observational Battery (devFOB; which is less extensive than the full FOB), but the reasons for the lower LOAEL detection rate for learning and memory assessment could not be determined. A major concern identified in the review, however, was the adequacy of the methods employed in these studies rather than on the importance of learning and memory to the proper assessment of brain function. Accordingly, a symposium was conducted to consider how the guidelines for tests of learning and memory might be improved. Four laboratories with established histories investigating the effects of chemical exposures during development on learning, memory, and attention, were invited to review the topic and offer recommendations, both theoretical and practical, on approaches to improve the assessment of these vital CNS functions. Reviewers were asked to recommend methods that are grounded in functional importance to CNS integrity, well-validated, reliable, and amenable to the context of regulatory studies as well as to basic research on the underlying processes they measure. This Introduction sets the stage for the reviews by providing the background and regulatory context for improved tests for learning and memory in DNT and other regulatory studies, such as single- or multi-generational studies where similar methods are incorporated., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Maneuvering safely through the environment is central to survival of all animals. The ability to do this depends on learning and remembering locations. This capacity is encoded in the brain by two systems: one using cues outside the organism (distal cues), allocentric navigation, and one using self-movement, internal cues and sometimes proximal cues, egocentric navigation. Allocentric navigation involves the hippocampus, entorhinal cortex, and surrounding structures (e.g., subiculum); in humans this system encodes declarative memory (allocentric, semantic, and episodic, i.e., memory for people, places, things, and events). This form of memory is assessed in laboratory animals by many methods, but predominantly the Morris water maze (MWM). Egocentric navigation involves the dorsal striatum and connected structures; in humans this system encodes routes and integrated paths and when over-learned becomes implicit or procedural memory. Several allocentric methods for rodents are reviewed and compared with the MWM with particular focus on the Cincinnati water maze (CWM). MWM advantages include minimal training, no food deprivation, ease of testing, reliable learning, insensitivity to differences in body weight and appetite, absence of non-performers, control methods for performance effects, repeated testing capability and other factors that make this test well-suited for regulatory studies. MWM limitations are also reviewed. Evidence-based MWM design and testing methods are presented. On balance, the MWM is arguably the preferred test for assessing learning and memory in basic research and regulatory studies and the CWM is recommended if two tests can be accommodated so that both allocentric (MWM) and egocentric (CWM) learning and memory can be effectively and efficiently assessed., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Use of silver nanoparticles (AgNPs) for their antimicrobial properties is widespread. Much of the previous work on the toxicity of AgNPs has been conducted in vitro or following oral or intravenous administration in vivo. Intranasal (IN) instillation of AgNPs mimics inhalation exposure and allows further exploration of the toxicity of these particles via respiratory tract exposure. The present study involved 1) single-dose exposures to assess tissue distribution and toxicity and 2) repeated exposures to assess behavioral effects of IN AgNP exposure (nominally uncoated 25 nm AgNP). AgNP deposition was localized in the liver, gut-associated lymphoid tissue, and brain. Decrease cellularity in spleen follicles was observed in treated mice, along with changes in cell number and populations in the spleen. The splenic GSH:GSSG ratio was also reduced following AgNP exposure. Expression of the oxidative stress-responsive gene Hmox1 was elevated in the hippocampus, but not cortex of treated mice, as was the level of HMOX1 protein. Mice receiving 7 days of IN exposure to 50 mg/kg AgNPs exhibited similar learning- and memory-related behaviors to control mice, except that treated mice spent significantly less time in the target quadrant of the Morris Water Maze during the acquisition phase probe trial. These findings indicate systemic distribution and toxicity following IN administration of AgNPs., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Prenatal maternal immune activation increases risk for schizophrenia and/or autism. Previous data suggest that maternal weight change in response to the immune activator polyinosinic-polycytidylic (Poly IC) in rats influences the severity of effect in the offspring as does the exposure period. We treated gravid Sprague-Dawley rats from E14 to 18 with 8mg/kg/day Poly IC or saline. The Poly IC group was divided into those that gained the least weight or lost (Poly IC (L)) and those that gained the most (Poly IC (H)) weight. There were no effects of Poly IC on anxiety (elevated zero-maze, open-field, object burying), or Morris water maze cued learning or working memory or Cincinnati water maze egocentric learning. The Poly IC (H) group males had decreased acoustic startle whereas Poly IC (L) females had reduced startle and increased PPI. Poly IC offspring showed exaggerated hyperactivity in response to amphetamine (primarily in the Poly IC (H) group) and attenuated hyperactivity in response to MK-801 challenge (primarily in the Poly IC (L) group). Poly IC (L) males showed reduced cued conditioned freezing; both sexes showed less time in the dark in a light-dark test, and the Poly IC groups showed impaired Morris water maze hidden platform acquisition and probe performance. The data demonstrate that offspring from the most affected dams were more affected than those from less reactive dams indicating that degree of maternal immune activation predicts severity of effects on offspring behavior., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Maneuvering safely through the environment is central to survival of all animals. The ability to do this depends on learning and remembering locations. This capacity is encoded in the brain by two systems: one using cues outside the organism (distal cues), allocentric navigation, and one using self-movement, internal cues and sometimes proximal cues, egocentric navigation. Allocentric navigation involves the hippocampus, entorhinal cortex, and surrounding structures (e.g., subiculum); in humans this system encodes declarative memory (allocentric, semantic, and episodic, i.e., memory for people, places, things, and events). This form of memory is assessed in laboratory animals by many methods, but predominantly the Morris water maze (MWM). Egocentric navigation involves the dorsal striatum and connected structures; in humans this system encodes routes and integrated paths and when over-learned becomes implicit or procedural memory. Several allocentric methods for rodents are reviewed and compared with the MWM with particular focus on the Cincinnati water maze (CWM). MWM advantages include minimal training, no food deprivation, ease of testing, reliable learning, insensitivity to differences in body weight and appetite, absence of non-performers, control methods for performance effects, repeated testing capability and other factors that make this test well-suited for regulatory studies. MWM limitations are also reviewed. Evidence-based MWM design and testing methods are presented. On balance, the MWM is arguably the preferred test for assessing learning and memory in basic research and regulatory studies and the CWM is recommended if two tests can be accommodated so that both allocentric (MWM) and egocentric (CWM) learning and memory can be effectively and efficiently assessed., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Although maternal cigarette smoking during pregnancy is a well-documented risk factor for a variety of adverse pregnancy outcomes, how prenatal cigarette smoke exposure affects postnatal neurobehavioral/cognitive development remains poorly defined. In order to investigate the cause of an altered behavioral phenotype, mice developmentally exposed to a paradigm of 'active' maternal cigarette smoke is needed. Accordingly, cigarette smoke exposed (CSE) and air-exposed C57BL/6J mice were treated for 6h per day in paired inhalation chambers throughout gestation and lactation and were tested for neurobehavioral effects while controlling for litter effects. CSE mice exhibited less than normal anxiety in the elevated zero maze, transient hypoactivity during a 1h locomotor activity test, had longer latencies on the last day of cued Morris water maze testing, impaired hidden platform learning in the Morris water maze during acquisition, reversal, and shift trials, and impaired retention for platform location on probe trials after reversal but not after acquisition or shift. CSE mice also showed a sexually dimorphic response in central zone locomotion to a methamphetamine challenge (males under-responded and females over-responded), and showed reduced anxiety in the light-dark test by spending more time on the light side. No differences on tests of marble burying, acoustic startle response with prepulse inhibition, Cincinnati water maze, matching-to-sample Morris water maze, conditioned fear, forced swim, or MK-801-induced locomotor activation were found. Collectively, the data indicate that developmental cigarette smoke exposure induces subnormal anxiety in a novel environment, impairs spatial learning and reference memory while sparing other behaviors (route-based learning, fear conditioning, and forced swim immobility). The findings add support to mounting evidence that developmental cigarette smoke exposure has long-term adverse effects on brain function., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Enhanced oxidative stress or deficient oxidative stress response in the brain is associated with neurodegenerative disorders and behavioral abnormalities. Previously we generated a knockout mouse line lacking the gene encoding glutamate-cysteine ligase modifier subunit (GCLM). Gclm(-/-) knockout (KO) mice are viable and fertile, yet exhibit only 9-35% of wild-type levels of reduced glutathione (GSH) in tissues, making them a useful model for chronic GSH depletion. Having the global absence of this gene, KO mice--from the time of conception and throughout postnatal life--experience chronic oxidative stress in all tissues, including brain. Between postnatal day (P) 60 and P100, we carried out behavioral phenotyping tests in adults, comparing male and female Gclm(-/-) with Gclm(-/-) wild-type (WT) littermates. Compared with WT, KO mice exhibited: subnormal anxiety in the elevated zero maze; normal overall exploratory open-field activity, but slightly more activity in the peripheral zones; normal acoustic startle and prepulse inhibition reactions; normal novel object recognition with increased time attending to the stimulus objects; slightly reduced latencies to reach a random marked platform in the Morris water maze; normal spatial learning and memory in multiple phases of the Morris water maze; and significantly greater hyperactivity in response to methamphetamine in the open field. These findings are generally in agreement with two prior studies on these mice and suggest that the brain is remarkably resilient to lowered GSH levels, implying significant reserve capacity to regulate reactive oxygen species-but with regional differences such that anxiety and stimulated locomotor control brain regions might be more vulnerable., (Copyright © 2012 Elsevier Inc. All rights reserved.)

In rats, neonatal (+)-methamphetamine (MA) exposure and maternal separation stress increase corticosterone during treatment and result in learning and memory impairments later in life. Early-life stress also changes later responses to acute stress. We tested the hypothesis that neonatal MA exposure would alter adult corticosterone after acute stress or MA challenge. Rats were treated with MA (10 mg/kg × 4/day), saline, or handling on postnatal (P) days 11-15 or 11-20 (days that lead to learning and memory impairments at this dose). As adults, corticosterone was measured before and after 15 min forced swim (FS) or 15 min forced confinement (FC), counterbalanced, and after an acute MA challenge (10 mg/kg) given last. FS increased corticosterone more than FC; order and stress type interacted but did not interact with treatment; treatment interacted with FS but not with FC. In the P11-15 regimen, MA-treated rats showed more rapid increases in corticosterone after FS than controls. In the P11-20 regimen, MA-treated rats showed a trend toward more rapid decrease in corticosterone after FS. No differences were found after MA challenge. The data do not support the hypothesis that neonatal MA causes changes in adult stress responsiveness to FS, FC, or an acute MA challenge., (Copyright © 2011 Elsevier Inc. All rights reserved.)

NPSR1 is a G protein coupled receptor expressed in multiple brain regions involved in modulation of stress. Central administration of NPS, the putative endogenous ligand of NPSR1, can induce hyperlocomotion, anxiolytic effects and activation of the HPA axis. The role of NPSR1 in the brain remains unsettled. Here we used NPSR1 gene-targeted mice to define the functional role of NPSR1 under basal conditions on locomotion, anxiety- and/or depression-like behavior, corticosterone levels, acoustic startle with prepulse inhibition, learning and memory, and under NPS-induced locomotor activation, anxiolysis, and corticosterone release. Male, but not female, NPSR1-deficient mice exhibited enhanced depression-like behavior in a forced swim test, reduced acoustic startle response, and minor changes in the Morris water maze. Neither male nor female NPSR1-deficient mice showed alterations of baseline locomotion, anxiety-like behavior, or corticosterone release after exposure to a forced swim test or methamphetamine challenge in an open-field. After intracerebroventricular (ICV) administration of NPS, NPSR1-deficient mice failed to show normal NPS-induced increases in locomotion, anxiolysis, or corticosterone release compared with WT NPS-treated mice. These findings demonstrate that NPSR1 is essential in mediating NPS effects on behavior., (Copyright 2010 Elsevier Ltd. All rights reserved.)

Rat neonatal methamphetamine exposure results in corticosterone release and learning and memory impairments in later life; effects also observed after neonatal stress. Previous attempts to test the role of corticosterone release after methamphetamine using corticosterone inhibitors were unsuccessful and adrenalectomy caused reductions in hippocampal serotonin greater than those caused by methamphetamine alone. Here we tested whether adrenal autotransplantation could be used to attenuate methamphetamine-induced corticosterone release without also altering the effects of the drug on serotonin. Adrenal autotransplantation surgery occurred on postnatal day 9 followed by methamphetamine or saline treatment from postnatal day 11-20 (10mg/kg/dosex4/day). Plasma corticosterone and hippocampal serotonin and 5-hydroxyindoleacetic acid were determined 30min following the first treatment on each day between postnatal days 11-20. Adrenal autotransplantation attenuated neonatal methamphetamine-induced corticosterone release by approximately 70% initially, approximately 55% midway through treatment, and approximately 25% by the end of treatment. Methamphetamine reduced serotonin and 5-hydroxyindoleacetic acid in the hippocampus in the ADXA rats to the same degree as in SHAM rats. The data show that neonatal adrenal autotransplantation is an effective method for partially reducing treatment-induced corticosterone release while providing sufficient corticosterone to sustain normal growth and development. The method should be applicable to other models of developmental stress/corticosterone release.

Rationale: In rats, neurotoxic doses of methamphetamine (MA) induce astrogliosis, long lasting monoamine reductions, reuptake transporter down-regulation, and learning impairments., Objective: We tested whether comparable effects occur in C57BL/6 mice., Method: C57BL/6 mice were treated with 10mg/kgs.c.x4 MA on a single day and evaluated at various intervals thereafter., Results: The neurotoxic dose regimen of MA caused the predicted acute hyperthermia and increased striatal glial fibrillary acidic protein and reduced neostriatal dopamine. The MA-treated mice were hypoactive 24h later but not 48h later. MA-treated mice also showed exaggerated initial hyperactivity after a pharmacological dose of MA used to stimulate locomotion followed by a later phase of hypoactivity compared to saline-treated mice. No differences were observed on learning or memory tests (novel object recognition, egocentric, or spatial learning/memory). MA-treated mice showed a trend toward increased prepulse inhibition but not baseline acoustic startle reactivity. After testing, MA-treated mice showed reduced neostriatal dopamine and increased basal plasma corticosterone., Conclusions: A neurotoxic/binge regimen of MA in mice that produces the typical pattern of neurotoxic changes to those seen in rats, results in few behavioral changes. This may limit the utility of C57BL/6 mice for modeling the cognitive and behavioral effects described in human MA users who show such changes even after prolonged abstinence.

The use of the club drugs 3,4-methylenedioxymethamphetamine (MDMA) and 5-methoxy-n,n-diisopropyltryptamine (Foxy) is of growing concern, especially as many of the effects, particularly during development, are unknown. The effects of these drugs upon homeostasis may be important since both are known to stimulate the hypothalamic-pituitary-adrenal axis. The purpose of this experiment was to examine alterations in rats in corticosterone and glucose following an acute exposure to these drugs at different stages of development: preweaning, juvenile, and adulthood. Both MDMA and Foxy increased corticosterone levels significantly at all ages examined, while glucose was elevated at all stages except at the juvenile time point (postnatal day 28). For both measures, there were no differences between the sexes with either drug. The data indicate that an acute exposure to these drugs alters CORT and glucose levels, raising the possibility that these changes may have effects on behavioral and cognitive function, as we and others have previously demonstrated., (Copyright (c) 2009 Elsevier Inc. All rights reserved.)

Developmental exposure to the dopamine D2/3 receptor agonist quinpirole is reported to induce D2 priming, impair Morris water maze performance, reduce acoustic startle prepulse inhibition (PPI), and alter locomotor activity. We treated rats from postnatal days 1-21 with the dose reported to induce these effects, 1.0 mg/kg/day, and two higher doses, 2.0 and 4.0 mg/kg/day, or saline. Offspring were tested in the Morris water maze, PPI, exploratory locomotor activity, activity after quinpirole and (+)-methamphetamine challenge, elevated zero maze, light-dark box, marble burying, straight channel swimming, and Cincinnati water maze. In the Morris water maze, all quinpirole groups had longer latencies on test days 3-5 of acquisition, but no effects on reversal or shifted-reduced platform trials. The quinpirole 4.0 mg/kg group had significantly reduced mean search distances on probe trials when combined across the 3 phases of testing but not separately. The male 4.0 mg/kg quinpirole group showed a greater increase in methamphetamine-stimulated activity during the first 10 min after drug challenge but not in the remainder of the 2 h test. No quinpirole effects were found for light-dark box, marble burying, exploratory locomotor activity, straight channel, Cincinnati water maze, or locomotor activity after quinpirole challenge. No effects were found on most measures in the elevated zero maze however the quinpirole 4.0 mg/kg females had longer latencies to enter an open quadrant. The results partially support prior Morris maze deficits induced by developmental quinpirole treatment but little evidence of dopamine D2/3 priming was found using locomotor activity with quinpirole or methamphetamine challenge or acoustic startle/PPI. The limited comparability to published data using developmental quinpirole exposure may be attributable to differences in experimental procedures or may be the result of quinpirole having limited effects. The data suggest that caution is warranted concerning the developmental efficacy of quinpirole.

3,4-Methlylenedioxymethamphetamine (MDMA) administration (4 x 15 mg/kg) on a single day has been shown to cause path integration deficits in rats. While most animal experiments focus on single binge-type models of MDMA use, many MDMA users take the drug on a recurring basis. The purpose of this study was to compare the effects of repeated single-day treatments with MDMA (4 x 15 mg/kg) once weekly for 5 weeks to animals that only received MDMA on week 5 and saline on weeks 1-4. In animals treated with MDMA for 5 weeks, there was an increase in time spent in the open area of the elevated zero maze suggesting a decrease in anxiety or increase in impulsivity compared to the animals given MDMA for 1 week and saline treated controls. Regardless of dosing regimen, MDMA treatment produced path integration deficits as evidenced by an increase in latency to find the goal in the Cincinnati water maze. Animals treated with MDMA also showed a transient hypoactivity that was not present when the animals were re-tested at the end of cognitive testing. In addition, both MDMA-treated groups showed comparable hyperactive responses to a later methamphetamine challenge. No differences were observed in spatial learning in the Morris water maze during acquisition or reversal but MDMA-related deficits were seen on reduced platform-size trials. Taken together, the data show that a single-day regimen of MDMA induces deficits similar to that of multiple weekly treatments.

In this study, brain derived neurotrophic factor (BDNF) and nerve growth factor (NGF) were examined at five time points [postnatal day (P)11, 15, 20, 21, and 68 (the latter with or without behavioral testing)] during and after P11-20 (+)-methamphetamine (MA) (10 mg/kg 4 x day) treatment. BDNF in MA-treated animals was elevated on P15 and P20 in the hippocampus but not in the hypothalamus and was unchanged on P11 and P21. On P68 (1 h after Morris water maze testing) MA-treated offspring showed a trend toward higher levels of BDNF in the hippocampus than saline-treated animals. MA treatment increased NGF levels in the hippocampus but only on P20. No effect of MA treatment was observed in the elevated zero maze. MA-treated offspring had increased latencies, cumulative distances, path lengths, and first bearings in the Morris water maze. The findings indicate that early MA exposure induces hippocampal BDNF increases that precede the later emergence of spatial learning deficits.

We have previously shown that P11-20 treatment with d-methamphetamine (MA) induces impaired spatial navigation in the Morris water maze (MWM), whereas P1-10 treatment does not. Little is known about the long-term behavioral consequences of MA during juvenile, adolescent, and early adult brain development. In dose-response experiments, we tested successive 10-day intervals of exposure to MA in rats (P21-30, P31-40, P41-50, and P51-60; four doses per day). MA dosing prior to P21 produces little or no toxicity; however, we observed an increased toxicity with advancing age. Across-age comparisons revealed no MWM acquisition or Cincinnati water maze (CWM) effects after MA treatment on P21-30 (2.5-10 mg/kg/dose), P31-40 (1.25-7.5 mg/kg/dose), or P51-60 (1.25-5.0 mg/kg/dose); however, significantly impaired MWM acquisition was observed after P41-50 MA treatment at the highest dose (6.25 mg/kg/dose). Learning in the CWM was also impaired in this group. No effects were seen at 1.25, 2.5, or 5 mg/kg/dose following P41-50 MA treatment. MWM reversal learning trials after P41-50 treatment showed a trend towards longer latency in all MA dose groups, but no effect on double-reversal trials. Reversal and double-reversal also showed no effects at the other exposure ages. No differences in straight channel swimming or cued learning in the MWM were seen after MA treatment at any exposure age. P41-50 is the periadolescent stage of brain development in rodents. The effects observed at this age may suggest a previously unrecognized period of susceptibility for MA-induced cognitive deficits.

A limited number of studies exist describing the effects of +/-3,4-methylenedioxymethamphetamine (MDMA) during perinatal development, although the number of MDMA users has increased dramatically, and this increase is greatest in people of child-bearing age. Previous experimental studies show that exposure to MDMA during part of the third trimester-equivalent (postnatal days P1-20 in rats) cause two distinct types of learning and memory deficits (sequential and spatial) if exposed on P11-20, but not if exposure occurs on P1-10. In the present study, we examined differences in the ability of neonatal rats to eliminate MDMA. Rat offspring were given a single dose of 20 mg/kg MDMA on either P1 or 11, and plasma was collected at 1 of 10 time points during a 10-h period. MDMA concentrations were assessed by liquid chromatography/mass spectrometry (LC/MS). Indices of absorption did not differ as a function of exposure age. Exposure age differences in the clearance rate and half-life of MDMA were observed, such that the P1-treated animals had a significantly more rapid clearance and a shorter half-life than P11-treated animals did. These changes are in the same direction as the behavioral differences reported previously between P1-10 and P11-20 MDMA exposure groups. However, the pharmacokinetic differences were not commensurate with the behavioral changes in that the clearance differences at the two ages are quantitative whereas the behavioral differences were qualitative (no effects from P1-10 exposure and large effects from P11-20). Although the data do not suggest a mechanism for the learning deficits, they indicate that pharmacokinetic differences may contribute to the effects seen when exposure is begun on P11.

Fenfluramine (FEN) is an amphetamine derivative with anorectic properties similar to amphetamine, but without the stimulatory or abuse potential. Administration of FEN produces an immediate release of serotonin as well as inhibits reuptake; ultimately FEN produces a decrease in serotonin stores in the central nervous system. We have previously shown that the administration of FEN to rats results in increased adrenal cortical hormones under resting conditions, without simultaneous elevations in adrenocorticotropin hormone (ACTH). We hypothesized that the adrenal output would be altered following stress and that the altered adrenal output would affect learning and memory, since the adrenal hormones influence learning and memory capability. In this series of experiments, we administered D,L-FEN (15 mg/kg) four times every 2 h on a single day to rats and investigated the effect on hormonal output following forced swim and the effect on sequential learning in the Cincinnati water maze and spatial learning in the Morris maze beginning 3 days after FEN administration. Animals that received FEN had increased corticosterone and aldosterone titers following forced swim relative to control animals, although no differences in ACTH or testosterone were noted. Animals exposed to FEN had lasting deficits in the Cincinnati water maze but not in the Morris water maze, regardless of testing order. These deficits in the Cincinnati water maze appear to be mediated by the elevation in adrenal output since adrenalectomy abolished the effect of FEN. Corticosterone levels were shown to be elevated during the behavioral testing period in animals exposed to FEN.