Nicotine therapy in adulthood reverses the synaptic and behavioral deficits elicited by prenatal exposure to phenobarbital

Negative affective states and cognitive impairments in nicotine dependence

Smokers have substantial individual differences in quit success in response to current treatments for nicotine dependence. This observation may suggest that different underlying motivations for continued tobacco use across individuals and nicotine cessation may require different treatments in different individuals. Although most animal models of nicotine dependence emphasize the positive reinforcing effects of nicotine as the major motivational force behind nicotine use, smokers generally report that other consequences of nicotine use, including the ability of nicotine to alleviate negative affective states or cognitive impairments, as reasons for continued smoking. These states could result from nicotine withdrawal, but also may be associated with premorbid differences in affective and/or cognitive function. Effects of nicotine on cognition and affect may alleviate these impairments regardless of their premorbid or postmorbid origin (e.g., before or after the development of nicotine dependence). The ability of nicotine to alleviate these symptoms would thus negatively reinforce behavior, and thus maintain subsequent nicotine use, contributing to the initiation of smoking, the progression to dependence and relapse during quit attempts. The human and animal studies reviewed here support the idea that self-medication for pre-morbid and withdrawal-induced impairments may be more important factors in nicotine addiction and relapse than has been previously appreciated in preclinical research into nicotine dependence. Given the diverse beneficial effects of nicotine under these conditions, individuals might smoke for quite different reasons. This review suggests that inter-individual differences in the diverse effects of nicotine associated with self-medication and negative reinforcement are an important consideration in studies attempting to understand the causes of nicotine addiction, as well as in the development of effective, individualized nicotine cessation treatments.

Impact of early life exposure to antiepileptic drugs on neurobehavioral outcomes based on laboratory animal and clinical research

Epilepsy affects approximately 1% of children under the age of 15, making it a very common neurological disorder in the pediatric population (Russ et al., 2012). In addition, ~0.4-0.8% of all pregnant women have some form of epilepsy (Hauser et al., 1996a,b; Borthen et al., 2009; Krishnamurthy, 2012). Despite the potential deleterious effects of antiepileptic drugs (AEDs) on the developing brain, their use is still required for seizure control in pregnant women (Krishnamurthy, 2012), and they represent the standard approach for treating children with epilepsy (Chu-Shore and Thiele, 2010; Quach et al., 2010; Verrotti et al., 2011). Even when AEDs are effective, there are potential side effects, including cognitive and affective changes or altered sleep and appetite. The consequences of AED exposure in development have been studied extensively (Canger et al., 1999; Modi et al., 2011a,b; Oguni, 2011). Despite intensive study, there is still debate about the long-term consequences of early life AED exposure. Here, we consider the evidence to date that AED exposure, either prenatally or in early postnatal life, has significant adverse effects on the developing brain and incorporate studies of laboratory animals as well as those of patients. We also note the areas of research where greater clarity seems critical in order to make significant advances. A greater understanding of the impact of AEDs on somatic, cognitive and behavioral development has substantial value because it has the potential to inform clinical practice and guide studies aimed at understanding the genetic and molecular bases of comorbid pathologies associated with common treatment regimens. Understanding these effects has the potential to lead to AEDs with fewer side effects. Such advances would expand treatment options, diminish the risk associated with AED exposure in susceptible populations, and improve the quality of life and health outcomes of children with epilepsy and children born to women who took AEDs during pregnancy.

Developmental sub-chronic exposure to chlorpyrifos reduces anxiety-related behavior in zebrafish larvae

Neurobehavioral disorders such as anxiety, autism, and attention deficit hyperactivity disorders are typically influenced by genetic and environmental factors. Although several genetic risk factors have been identified in recent years, little is known about the environmental factors that either cause neurobehavioral disorders or contribute to their progression in genetically predisposed individuals. One environmental factor that has raised concerns is chlorpyrifos, an organophosphate pesticide that is widely used in agriculture and is found ubiquitously in the environment. In the present study, we examined the effects of sub-chronic chlorpyrifos exposure on anxiety-related behavior during development using zebrafish larvae. We found that sub-chronic exposure to 0.01 or 0.1 μM chlorpyrifos during development induces specific behavioral defects in 7-day-old zebrafish larvae. The larvae displayed decreases in swim speed and thigmotaxis, yet no changes in avoidance behavior were seen. Exposure to 0.001 μM chlorpyrifos did not affect swimming, thigmotaxis, or avoidance behavior and exposure to 1 μM chlorpyrifos induced behavioral defects, but also induced defects in larval morphology. Since thigmotaxis, a preference for the edge, is an anxiety-related behavior in zebrafish larvae, we propose that sub-chronic chlorpyrifos exposure interferes with the development of anxiety-related behaviors. The results of this study provide a good starting point for examination of the molecular, cellular, developmental, and neural mechanisms that are affected by environmentally relevant concentrations of organophosphate pesticides. A more detailed understanding of these mechanisms is important for the development of predictive models and refined health policies to prevent toxicant-induced neurobehavioral disorders.

Mouse models for studying genetic influences on factors determining smoking cessation success in humans

Humans differ in their ability to quit using addictive substances, including nicotine, the major psychoactive ingredient in tobacco. For tobacco smoking, a substantial body of evidence, largely derived from twin studies, indicates that approximately half of these individual differences in ability to quit are heritable genetic influences that likely overlap with those for other addictive substances. Both twin and molecular genetic studies support overlapping influences on nicotine addiction vulnerability and smoking cessation success, although there is little formal analysis of the twin data that support this important point. None of the current datasets provides clarity concerning which heritable factors might provide robust dimensions around which individuals differ in ability to quit smoking. One approach to this problem is to test mice with genetic variations in genes that contain human variants that alter quit success. This review considers which features of quit success should be included in a comprehensive approach to elucidate the genetics of quit success, and how those features may be modeled in mice.

Quantitative Molecular Imaging of Neuronal Nicotinic Acetylcholine Receptors in the Human Brain with A-85380 Radiotracers

Neuronal nicotinic acetylcholine receptors (nAChRs) have been implicated in a spectrum of cognitive functions as well as psychiatric and neurodegenerative disorders, including tobacco addiction and Alzheimer's Disease. The examination of neuronal nAChRs in living humans is a relatively new field. Researchers have developed brain-imaging radiotracers for nAChRs, with radiolabeled A-85380 compounds having the most widespread use. We provide a brief background on nAChRs, followed by a discussion of the development and application of A-85380 radiotracers in human imaging studies. We describe potential future studies using nicotinic receptor radioligands for the study of tobacco addiction, including the mechanism of action of the smoking-cessation therapy varenicline. Throughout this review, we focus on the significant potential that resides in the identification and quantification of nAChRs in the living human brain.

Reversal of chlorpyrifos neurobehavioral teratogenicity in mice by allographic transplantation of adult subventricular zone-derived neural stem cells

Neurobehavioral teratogenicity can be reversed with transplantation of neural stem cells. However, the usefulness of this therapy would be greatly enhanced by employing adult stem cells. In pursuit of this this goal, we developed a model that uses subventricular zone (SVZ) cells. HS/Ibg mice were exposed prenatally to chlorpyrifos on gestational days 9-18 (3 mg/kg/day, SC) in order to induce deficits in their performance in the Morris water maze test. Both the control and the exposed offspring were transplanted with SVZ cells (or vehicle) on postnatal day 35; this actually represents an allogenic transplantation, because the HS/Ibg strain is a heterogeneous stock. The transplanted cells were later observed in the host brain by DiI tracing, and their initial differentiation to cholinergic neurons and astrocytes was ascertained. On postnatal day 80, animals that had been exposed prenatally to chlorpyrifos displayed impaired Morris water maze performance, requiring more time to reach the platform. Transplantation of adult SVZ-derived neural stem cells (NSC) reversed the deficits. Applying autologous transplantation provides an important demonstration that the methodological obstacles of immunological rejection and the ethical concerns related to using embryonic stem cells may be successfully bypassed in developing stem cell therapies for neurodevelopmental disorders.

Survival, differentiation, and reversal of heroin neurobehavioral teratogenicity in mice by transplanted neural stem cells derived from embryonic stem cells

Cell therapies in animal models of neurobehavioral defects are normally derived from neural stem cells (NSC) of the developing cortex. However, the clinical feasibility of NSC therapies would be greatly improved by deriving transplanted cells and from a tissue culture source that is self-renewing, containing cells that potentially differentiate into the desired neuronal phenotypes. These cultures can be engineered to contain the appropriate factors to support their therapeutic action and likely evoke lesser immune reactions. In the current study, we employed our model of mice neurobehaviorally impaired via prenatal exposure to heroin, to test the therapeutic efficacy of NSC derived from murine embryonic stem cells culture (ESC). The culture contained elongated bipolar cells, 90% of which are positive for nestin, the intermediate filament protein found in neural precursors. After removal of growth factors, the NSC differentiated into neurons (34.0% +/- 3.8% NF-160 positive), including cholinergic cells (ChAT positive), oligodendrocytes (29.9% +/- 4.2% O(4)), and astrocytes (36.1% +/- 4.7% GFAP positive). Reverse transcriptase polymerase chain reaction (RT-PCR) analysis confirmed the immunocytochemical findings. Mice made deficient in Morris maze behavior by prenatal heroin exposure (10 mg/kg heroin s.c. on gestational days 9-18) were transplanted into the hippocampus region on postnatal day 35 with the ES culture-derived NSC (ES-NSC) labeled with dialkylcarbocyanine (Dil) cell tracker. Dil+ and NF160+ cells were detected in the hippocampal region (50% +/- 8% survival). The transplantation completely restored maze performance to normal; e.g., on day 3, transplantation improved the behavior from the deficient level of 11.9-sec latency to the control of 5.6-sec latency (44.5% improvement).

Neurobehavioral teratogenicity of perfluorinated alkyls in an avian model

Perfluorinated alkyls are widely-used agents that accumulate in ecosystems and organisms because of their slow rate of degradation. There is increasing concern that these agents may be developmental neurotoxicants and the present study was designed to develop an avian model for the neurobehavioral teratogenicity of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Fertilized chicken eggs were injected with 5 or 10mg/kg of either compound on incubation day 0. On the day of hatching, imprinting behavior was impaired by both compounds. We then explored underlying mechanisms involving the targeting of protein kinase C (PKC) isoforms (alpha, beta, gamma) in the intermedial part of the hyperstriatum ventrale, the region most closely associated with imprinting. With PFOA exposure, cytosolic PKC concentrations were significantly elevated for all three isoforms; despite the overall increase in PKC expression, membrane-associated PKC was unaffected, indicating a defect in PKC translocation. In contrast, PFOS exposure evoked a significant decrease in cytosolic PKC, primarily for the beta and gamma isoforms, but again without a corresponding change in membrane-associated enzyme; this likely partial, compensatory increases in translocation to offset the net PKC deficiency. Our studies indicate that perfluorinated alkyls are indeed developmental neurotoxicants that affect posthatch cognitive performance but that the underlying synaptic mechanisms may differ substantially among the various members of this class of compounds, setting the stage for disparate outcomes later in life.

Reversal of chlorpyrifos neurobehavioral teratogenicity in mice by nicotine administration and neural stem cell transplantation

Identifying the mechanisms underlying the adverse effects of developmental neurotoxicants enables the design of therapies that can potentially reverse neurobehavioral deficits in adulthood. We administered chlorpyrifos (CPF), a model organophosphate pesticide to pregnant mice and identified visuospatial deficits in adult offspring using performance in the Morris maze. We then evaluated two strategies to reverse the effects, nicotine administration and transplantation of neural stem cells. Daily administration of nicotine prior to behavioral testing did not alter maze performance by itself, but completely reversed the deficits evoked by prenatal CPF exposure. Similarly, control animals grafted with neural stem cells in adolescence did not show any alterations in behavioral performance as adults, but the grafts completely reversed the effects of prenatal CPF treatment. This study thus provides a model for the development and application of both pharmacologic and cell-based therapies to offset the effects of neurobehavioral teratogens.

Consumption of a high-fat diet in adulthood ameliorates the effects of neonatal parathion exposure on acetylcholine systems in rat brain regions

BACKGROUND

Developmental exposure to a wide variety of developmental neurotoxicants, including organophosphate pesticides, evokes late-emerging and persistent abnormalities in acetylcholine (ACh) systems. We are seeking interventions that can ameliorate or reverse the effects later in life.

OBJECTIVES

We administered parathion to neonatal rats and then evaluated whether a high-fat diet begun in adulthood could reverse the effects on ACh systems.

METHODS

Neonatal rats received parathion on postnatal days 1-4 at 0.1 or 0.2 mg/kg/day, straddling the cholinesterase inhibition threshold. In adulthood, half the animals were switched to a high-fat diet for 8 weeks. We assessed three indices of ACh synaptic function: nicotinic ACh receptor binding, choline acetyltransferase activity, and hemicholinium-3 binding. Determinations were performed in brain regions comprising all the major ACh projections and cell bodies.

RESULTS

Neonatal parathion exposure evoked widespread abnormalities in ACh synaptic markers, encompassing effects in brain regions possessing ACh projections and ACh cell bodies. In general, males were affected more than females. Of 17 regional ACh marker abnormalities (10 male, 7 female), 15 were reversed by the high-fat diet.

CONCLUSIONS

A high-fat diet reverses neurodevelopmental effects of neonatal parathion exposure on ACh systems. This points to the potential for nonpharmacologic interventions to offset the effects of developmental neurotoxicants. Further, cryptic neurodevelopmental deficits evoked by environmental exposures may thus engender a later preference for a high-fat diet to maintain normal ACh function, ultimately contributing to obesity.

Sexual function in adult male rats after prenatal modulation of the cholinergic system

Prenatal administration of the n-cholinolytic ganglerone to pregnant female rats at different periods of gestation was found to lead to long-term changes in sexual behavior in pubescent offspring: there was a reduced dynamic of acquiring sexual experience and a very low level of sexual activity, with significant impairment to the motivational and ejaculatory components of sexual behavior. The number of males with reduced sexual activity in the experimental groups was significantly greater than that in control offspring. The results obtained here provide evidence that impairments of sexual function in adult offspring induced by prenatal administration of the n-cholinolytic ganglerone at 9-11 and 12-14 days of gestation and, to a lesser extent, the m-cholinolytic metamyzil at 9-11 days of gestation, were due to impairment to the central mechanisms regulating sexual function due to stable changes in neurotransmitter activity in the hippocampus and hypothalamus, along with a significant reduction in the blood testosterone level.

A mechanism-based complementary screening approach for the amelioration and reversal of neurobehavioral teratogenicity

The identification of mechanisms and outcomes for neurobehavioral teratogenesis is critical to our ability to develop therapies to ameliorate or reverse the deleterious effects of exposure to developmental neurotoxicants. We established mechanistically-based complementary models for the study of cholinergic systems in the mouse and the chick, using both environmental neurotoxicants (chlorpyrifos, perfluoroalkyls) and drugs of abuse (heroin, nicotine, PCP). Behavioral evaluations were made using the Morris maze in the mouse, evaluating visuospatial memory related to hippocampal cholinergic systems, and imprinting in the chick, examining behavior dependent on cholinergic innervation of the IMHV. In both models we demonstrated the dependence of neurobehavioral deficits on impairment of cholinergic receptor-induced expression, and translocation of specific PKC isoforms. Understanding this mechanism, we were able to reverse both the synaptic and behavioral deficits with administration of neural progenitors. We discuss the prospects for clinical application of neural progenitor therapy, emphasizing protocols for reducing or eliminating immunologic rejection, as well as minimizing invasiveness of procedures through development of intravenous administration protocols.

Protein kinase C is a target for diverse developmental neurotoxicants: transcriptional responses to chlorpyrifos, diazinon, dieldrin and divalent nickel in PC12 cells

Unrelated developmental neurotoxicants can elicit similar functional outcomes, whereas agents in the same class may differ. We compared two organophosphate insecticides (chlorpyrifos, diazinon) with an organochlorine (dieldrin) and a metal (Ni(2+)) for similarities and differences in their effects on gene expression encoding subtypes of protein kinase C and their modulators, a cell signaling cascade that integrates the actions of neurotrophic factors involved in brain development. We conducted evaluations in PC12 cells, a model for neuronal development, with each agent introduced at 30 microM for 24 or 72 h, treatments devoid of cytotoxicity. Chlorpyrifos evoked by far the largest effect, with widespread upregulation of multiple genes; the effects were greater during neurodifferentiation than when cells were exposed prior to differentiation. Diazinon had smaller and less widespread effects, consistent with its lesser long-term impact on synaptic function and behavior noted for in vivo exposures in developing rats. Surprisingly, the effects of diazinon, dieldrin and Ni(2+) showed basic similarities despite the fact that all three come from different classes of toxicants. Our findings provide some of the first evidence for a specific mechanistic cascade contributing to the cholinesterase-independent developmental neurotoxicant actions of chlorpyrifos and its differences from diazinon, while at the same time identifying mechanistic convergence between otherwise unrelated toxicants that provides predictions about common neurodevelopmental outcomes. These results further show how combined use of cell cultures and microarray technology can guide future in vivo work on diverse developmental neurotoxicants.

Fetal mechanisms in neurodevelopmental disorders

Normal development of the central nervous system depends on complex, dynamic mechanisms with multiple spatial and temporal components during gestation. Neurodevelopmental disorders may originate during fetal life from genetic as well as intrauterine and extrauterine factors that affect the fetal-maternal environment. Fetal neurodevelopment depends on cell programs, developmental trajectories, synaptic plasticity, and oligodendrocyte maturation, which are variously modifiable by factors such as stress and endocrine disruption, exposure to pesticides such as chlorpyrifos and to drugs such as terbutaline, maternal teratogenic alleles, and premature birth. Current research illustrates how altered fetal mechanisms may affect long-term physiological and behavioral functions of the central nervous system more significantly than they affect its form, and these effects may be transgenerational. This research emphasizes the diversity of such prenatal mechanisms and the need to expand our understanding of how, when altered, they may lead to disordered development, the signs of which may not appear until long after birth.

Transplantation of neural progenitors enhances production of endogenous cells in the impaired brain

Grafting of neural progenitors has been shown to reverse a wide variety of neurobehavioral defects. While their role of replacing injured cells and restoring damaged circuitries has been shown, it is widely accepted that this cannot be the only mechanism, as therapy can occur even when an insufficient number of transplanted cells are found. We hypothesized that one major mechanism by which transplanted neural progenitors exert their therapeutic effect is by enhancing endogenous cells production. Consequently, in an allographic model of transplantation, prenatally heroin-exposed genetically heterogeneous (HS) mice were made defective in their hippocampal neurobehavioral function by exposing their mothers to heroin (10 mg kg(-1) heroin on gestation days 9-18). Hippocampal damage was confirmed by deficient performance in the Morris maze (P<0.009), and decreased production of endogenous cells in the dentate gyrus by 39% was observed. On postnatal day 35, they received an HS-derived neural progenitors transplant followed by repeated bromodeoxyuridine injections. The transplant returned endogenous cells production to normal levels (P<0.006) and reversed the behavioral defects (P<0.03), despite the fact that only 0.0334% of the transplanted neural progenitors survived and that they differentiated mainly to astrocytes. An immunological study demonstrated the presence of macrophages and T cells as a possible explanation for the paucity of the transplanted cells. This study suggests one mechanism for the therapeutic action of neural progenitors, the enhancement of the production of endogenous cells, pointing to future clinical applications in this direction by use of neural progenitors or by analogous cell-inducing techniques.

Reversal of heroin neurobehavioral teratogenicity by grafting of neural progenitors

A major objective in identifying the mechanisms underlying neurobehavioral teratogenicity in an animal model is the possibility of designing therapies that reverse or offset teratogen-induced neural damage. In our previous studies, we identified deficits in hippocampal muscarinic cholinergic receptor-induced translocation of protein kinase C (PKC) gamma as the likely central factor responsible for the adverse behavioral effects of pre-natal heroin exposure. Neural progenitors (NP) have the ability to recover behavioral deficits after focal hippocampal damage. Therefore, we explored whether behavioral and synaptic defects could be reversed in adulthood by neural progenitor grafting. Pregnant mice were injected daily with 10 mg/kg of heroin on gestational days 9-18. In adulthood, offspring showed deficits in the Morris maze, a behavior dependent on the integrity of septohippocampal cholinergic synaptic function, along with the loss of the PKCgamma and PKCbetaII responses to cholinergic stimulation. Mice that were exposed pre-natally to heroin and vehicle control mice were then grafted in adulthood with NP. Importantly, most grafted cells differentiated to astrocytes. NP reversed the behavioral deficits (p = 0.0043) and restored the normal response of hippocampal PKCgamma and PKCbetaII (p = 0.0337 and p = 0.0265 respectively) to cholinergic receptor stimulation. The effects were specific as the PKCalpha isoform, which is unrelated to the behavioral deficits, showed almost no changes. Neural progenitor grafting thus offers an animal model for reversing neurobehavioral deficits originating in septohippocampal cholinergic defects elicited by pre-natal exposure to insults.

Mechanism-Based Approaches for the Reversal of Drug Neurobehavioral Teratogenicity

Understanding the mechanism of neurobehavioral teratogenicity is the primary prerequisite for reversal of the defect. Progress in such studies can be best achieved if the investigation focuses on behaviors related to a specific brain region and innervation. Our model focused on teratogen-induced deficits in hippocampus-related eight-arm and Morris maze behaviors. Different "cholinergic" teratogens, mainly heroin, induced both pre- and postsynaptic hyperactivity in the hippocampal cholinergic innervation that terminated in desensitization of Protein Kinase C (PKC) isoforms to cholinergic receptor stimulation. Understanding this mechanism enabled its reversal with a pharmacological therapy-nicotine infusion. Studies by others provided similar findings by targeting the deficits respective to the model investigated. Consistently, destruction of the A10-septal dopaminergic pathways that downregulate the septohippocampal cholinergic innervation ameliorated maze performance. Grafting of embryonic differentiated cholinergic cells or neural progenitors similarly reversed the biochemical/molecular alterations and the resulting deficits. Reversal therapies offer a model for the understanding of neurobehavioral teratogenicity and, clinically, offer a model for potential treatment of these deficits. Whereas neural progenitor grafting appears to be the most effective treatment, pharmacological reversal with nicotine infusion seems to possess the most feasible and immediate therapy for neurobehavioral birth defects produced by various teratogens, including drugs. This is true even though the effect of pharmacological therapies is diffuse, affecting multiple areas of the brain. "Everybody is talking about the weather but nobody does anything about it." (Mark Twain).

Disruption of the development of cholinergic-induced translocation/activation of PKC isoforms after prenatal heroin exposure

Prenatal exposure of mice to heroin resulted in behavioral deficits present at adulthood, and related to septohippocampal cholinergic innervation accompanied by both pre- and postsynaptic cholinergic hyperactivity; including an increase in membrane PKC activity, and a desensitization of PKC to cholinergic input, which correlated highly with the behavioral performance, and was reversed by cholinergic grafting. The effect was shown in the behaviorally relevant PKCgamma and beta whereas the less behaviorally relevant PKCalpha isoform was not affected. The present study was designed to establish the effect of heroin exposure on the expression of the PKC isoforms level and on the more functionally relevant cholinergic translocation/activation of the isoforms throughout postnatal development. The hippocampi of mice pups, exposed to heroin transplacentally, were assayed after incubation with carbachol for PKC isoforms on postnatal days (PN) 1, 7, 14, 21, 30 and 50. Prenatal heroin exposure increased basal PKCgamma, beta and alpha levels. PKCgamma and alpha levels returned to control levels on PN50. While in PKCbeta, this increase lasted until PN50. Translocation/activation of the PKC isoforms gamma and beta by cholinergic receptor stimulation was present from PN1, concurrent with the presence of the isoforms. Prenatal exposure to heroin completely abolished the translocation/activation throughout the entire postnatal development. This defect was shown from the very beginning, PN1, the day when the PKC isoforms appear. The results suggest that the PKCgamma and beta isoforms are functional concurrent with their developmental appearance. Unlike findings on some other teratogens, the prenatal heroin effect on the isoforms function is similar throughout postnatal development.

A chick model for the mechanisms of mustard gas neurobehavioral teratogenicity

The chemical warfare blistering agent, sulfur mustard (SM), is a powerful mutagen and carcinogen. Due to its similarity to the related chemotherapy agents nitrogen mustard (mechlorethamine), it is expected to act as a developmental neurotoxicant. The present study was designed to establish a chick model for the mechanisms of SM on neurobehavioral teratogenicity, free of confounds related to mammalian maternal effects. Chicken eggs were injected with SM at a dose range of 0.0017-17.0 microg/kg of egg, which is below the threshold for dysmorphology, on incubation days (ID) 2 and 7, and then tests were conducted posthatching. Exposure to SM elicited significant deficits in the intermedial part of the hyperstriatum ventrale (IMHV)-related imprinting behavior. Parallel decreases were found in the level of membrane PKCgamma in the IMHV, while eliciting no net change in cytosolic PKCgamma. The chick, thus, provides a suitable model for the rapid evaluation of SM behavioral teratogenicity and elucidation of the mechanisms underlying behavioral anomalies. The results obtained, using a model that controls for confounding maternal effects, may be replicated in the mammalian model and provide the groundwork for studies designed to offset or reverse the SM-induced neurobehavioral defects in both avian and mammals.