Withdrawal from repeated nicotine vapor exposure increases somatic signs of physical dependence, anxiety-like behavior, and brain reward thresholds in adult male rats.

Nicotine vapor consumption via electronic nicotine delivery systems has increased over the last decade. While prior work has shed light on the health effects of nicotine vapor inhalation, its unique effects on the brain and behavior have not been thoroughly explored. In this study we assessed markers of withdrawal following 14 days of nicotine vapor exposure. For Experiment 1, 21 adult male rats were exposed to ambient air or 6, 12, or 24 mg/mL nicotine vapor for 14 consecutive days. Following exposure on day 14, rats were injected with the nicotinic receptor antagonist mecamylamine (3.0 mg/mL) and assessed for somatic withdrawal signs and anxiety-like behavior in the elevated plus maze. For Experiment 2, 12 adult male rats were tested for intracranial self-stimulation (ICSS) immediately following exposure to vehicle vapor (50%/50%, vegetable glycerin/propylene glycol) or 24 mg/mL nicotine vapor, for 14 consecutive days. ICSS behavior was assessed for an additional 14 days, following cessation of repeated vapor exposure. Results reveal that rats with repeated nicotine vapor exposure display an increase in behavioral indicators of withdrawal following injection of mecamylamine (precipitated withdrawal). Additionally, increases in ICSS stimulation thresholds, indicative of reduced brain reward sensitivity, persist following cessation of repeated nicotine vapor exposure (spontaneous withdrawal). These data suggest that repeated e-cigarette use leads to nicotine dependence and withdrawal that affects behavior and brain reward function. Further characterization of the health effects of nicotine vapor is necessary to improve treatment strategies for nicotine use disorder and public health policies related to novel nicotine delivery systems.

Sex and diet-dependent gene alterations in human and rat brains with a history of nicotine exposure.

Introduction: Chronic nicotine exposure induces changes in the expression of key regulatory genes associated with metabolic function and neuronal alterations in the brain. Many bioregulatory genes have been associated with exposure to nicotine, but the modulating effects of sex and diet on gene expression in nicotine-exposed brains have been largely unexplored. Both humans and rodents display motivation for nicotine use and the emergence of withdrawal symptoms during abstinence. Research comparing pre-clinical models with human subjects provides an important opportunity to understand common biomarkers of the harmful effects of nicotine as well as information that may help guide the development of more effective interventions for nicotine cessation. Methods: Human postmortem dorsolateral prefrontal cortex (dLPFC) tissue BA9 was collected from female and male subjects, smokers and non-smokers (N = 12 per group). Rat frontal lobes were collected from female and male rats that received a regular diet (RD) or a high-fat diet (HFD) (N = 12 per group) for 14 days following implantation of a osmotic mini-pump (Alzet) that delivered nicotine continuously. Controls (control-s) received a sham surgical procedure. RNA was extracted from tissue from human and rat samples and reversed-transcribed to cDNA. Gene expression of CHRNA10 (Cholinergic receptor nicotinic alpha 10), CERKL (Ceramide Kinase-Like), SMYD1 (SET and MYD Domin Containing 1), and FA2H (Fatty Acid 2-Hydrolase) in humans was compared to rats in each subset of groups and quantified by qPCR methods. Additionally, protein expression of FA2H was analyzed by immunohistochemistry (IHC) in human dLPFC. Results: Humans with a history of smoking displayed decreased CHRNA10 (p = 0.0005), CERKL (p ≤ 0.0001), and SMYD1 (p = 0.0005) expression and increased FA2H (p = 0.0097) expression compared to non-smokers (p < 0.05). Similar patterns of results were observed in nicotine exposed vs. control rats. Interestingly, sex-related differences in gene expression for CERKL and FA2H were observed. In addition, ANCOVA analysis showed a significant effect of nicotine in a sex-different manner, including an increase in CERKL in male and female rats with RD or HFD. In rats exposed to an HFD, FA2H gene expression was lower in nicotine-treated rats compared to RD rats treated with nicotine. Protein expression of FA2H (p = 0.001) by IHC was significantly higher in smokers compared to non-smokers. Conclusion: These results suggest that a history of long-term nicotine exposure in humans alters the expression of sphingolipid metabolism-related (CERKL, SMYD1, and FA2H) and neuronal (CHRNA10) marker genes similarly as compared to rats. Sex- and diet-dependent differences appear in nicotine-exposed rats, critical in regulating sphingolipid metabolism and nicotinic acetylcholine receptors. This research enhances the construct validity of rat models of nicotine usage by showing a similar pattern of changes in gene expression in human subjects with a smoking history.

Effectiveness of pharmacotherapies for diabetes on nicotine, food, and water intake in insulin-resistant rats.

The intersectionality between diabetes medications and nicotine consumption was assessed in female and male rats. Briefly, the rats were fed a high-fat diet (HFD) or regular diet (RD) for 4 weeks. Then separate groups received vehicle or a low dose of streptozotocin (STZ; 25 mg/kg). Three days later, insulin resistance was assessed by measuring plasma glucose levels for 180 min following an injection of insulin (0.75 U/kg). The rats were then prepared with jugular catheters, and they were given 23 h access to nicotine intravenous self-administration (IVSA) in 4 days cycles with 3 days of forced abstinence in their home cages where they consumed their respective diet. During the IVSA sessions, operant responses for food and water and changes in body weight were recorded. Prior to administration of the pharmacotherapies, the rats were given access to two doses of nicotine (0.015 then 0.03 mg/kg for the remainder of the study). Then, daily injections of the pharmacotherapies were given at the onset of dark cycle (6 p.m.) in the following order: 1) dapagliflozin (3.0 then 10.0 mg/kg), 2) insulin (0.75 U/kg twice), and 3) bromocriptine (3.0 then 10.0 mg/kg). The results suggest that our HFD+STZ regiment induced insulin resistance in female and male rats. Also, the HFD-fed rats displayed higher nicotine intake than RD controls, regardless of sex. Administration of insulin, but not dapagliflozin or bromocriptine, normalized nicotine intake in HFD-fed rats to control levels. These results have clinical implications regarding the potential efficacy of insulin to control excessive nicotine intake in persons with diabetes.

Amino acid systems in the interpeduncular nucleus are altered in a sex-dependent manner during nicotine withdrawal.

Prior work in male rodents established that the medial habenula-interpeduncular nucleus (MHb-IPN) pathway modulates nicotine withdrawal. Specifically, withdrawal severity has been closely associated with inhibitory tone in the IPN via interneurons that release γ-aminobutyric acid (GABA). Inhibitory tone in the IPN is regulated by projections from the MHb that co-release glutamate and acetylcholine. Within the IPN, inhibitory tone is also regulated via corticotropin-releasing factor type 1 (CRF1) receptors that control GABA release from local interneurons. This study extends previous work by comparing sex differences in GABA, glutamate, as well serotonin levels in the IPN during precipitated nicotine withdrawal. Sex differences in withdrawal-induced neurochemical effects were also compared following systemic administration of a CRF1 receptor antagonist. The results revealed that there were no group differences in serotonin levels in the IPN. A major finding was that females displayed a larger withdrawal-induced increases in GABA levels in the IPN than males. Also, withdrawal increased IPN glutamate levels in a similar manner in females and males. Blockade of CRF1 receptors produced a larger suppression of the withdrawal-induced increases in GABA levels in the IPN of females versus males, an effect that was likely related to the robust increase in glutamate following administration of the CRF1 receptor antagonist in females. These data suggest that amino acid systems in the IPN modulate sex differences in the behavioral effects of nicotine withdrawal. Furthermore, our data imply that medications that target stress-induced activation of the IPN may reduce withdrawal severity, particularly in females.

Insulin restores the neurochemical effects of nicotine in the mesolimbic pathway of diabetic rats.

This study examined whether insulin modulates the neurochemical effects of nicotine in the mesolimbic pathway of diabetic rats. The rats received vehicle or streptozotocin (STZ) to induce hypoinsulinemia. A subset of STZ-treated rats was implanted with insulin pellets that rapidly normalized glucose levels. Two-weeks later, dialysis probes were implanted into the nucleus accumbens (NAc) and ipsilateral ventral tegmental area (VTA). The next day, dialysate samples were collected during baseline and then following systemic administration of nicotine. Samples were also collected following intra-VTA administration of the gamma-aminobutyric acid (GABA)A receptor antagonist, bicuculline. Dopamine, GABA, glutamate, and acetylcholine (ACh) levels were assessed using liquid chromatography/mass spectrometry (LC/MS). The results revealed that vehicle-treated rats displayed a nicotine-induced increase in NAc dopamine levels. In contrast, STZ-treated rats did not display any changes in NAc dopamine following nicotine administration, an effect that was likely related to a concomitant increase in GABA and decrease in glutamate levels in both the NAc and VTA. Intra-VTA administration of bicuculline increased NAc dopamine in vehicle-treated rats, and this effect was absent in STZ-treated rats. Vehicle-treated rats displayed a nicotine-induced increase in ACh levels in the NAc (but not VTA), an effect that was lower in the NAc of STZ-treated rats. Insulin supplementation normalized the neurochemical effects of nicotine in the NAc and VTA of STZ-treated rats, suggesting that insulin modulates the neurochemical effects of nicotine in the mesolimbic pathway of diabetic rats.

Estradiol promotes and progesterone reduces anxiety-like behavior produced by nicotine withdrawal in female rats.

This study assessed sex differences and the role of ovarian hormones in nicotine withdrawal. Study 1 compared physical signs, anxiety-like behavior, and corticosterone levels in male, intact female, and ovariectomized (OVX) female rats during nicotine withdrawal. Estradiol (E2) and progesterone levels were also assessed in intact females that were tested during different phases of the 4-day estrous cycle. Study 2 assessed the role of ovarian hormones in withdrawal by comparing the same measures in OVX rats that received vehicle, E2, or E2+progesterone prior to testing. Briefly, rats received a sham surgery or an ovariectomy procedure. Fifteen days later, rats were prepared with a pump that delivered nicotine for 14 days. On the test day, rats received saline or the nicotinic receptor antagonist, mecamylamine to precipitate withdrawal. Physical signs and anxiety-like behavior were assessed on the elevated plus maze (EPM) and light-dark transfer (LDT) tests. During withdrawal, intact females displayed greater anxiety-like behavior and increases in corticosterone levels as compared to male and OVX rats. Females tested in the estrus phase (when E2 is relatively low) displayed less anxiety-like behavior and had lower corticosterone levels versus all other phases. Anxiety-like behavior and corticosterone levels were positively correlated with E2 and negatively correlated with progesterone levels. Intact females displaying high E2/low progesterone showed greater anxiety-like behavior and corticosterone levels as compared to females displaying low E2/high progesterone. Lastly, OVX-E2 rats displayed greater anxiety-like behavior than OVX-E2+progesterone rats. These data suggest that E2 promotes and progesterone reduces anxiety-like behavior produced by nicotine withdrawal.

Sex differences in cholinergic systems in the interpeduncular nucleus following nicotine exposure and withdrawal.

The medial habenula-interpeduncular nucleus (MHb-IPN) pathway modulates negative affective states produced by nicotine withdrawal. Sex differences in the contribution of acetylcholine (ACh) systems in this pathway have not been explored. Thus, this study assessed ACh levels and gene expression of α- and ß-containing nicotinic acetylcholine receptor (nAChR) subunits in the IPN of female and male rats following nicotine treatment and withdrawal. Rats were prepared with a pump that delivered nicotine for 14 days, and naïve controls received a sham surgery. In Study 1, rats were prepared with a probe in the IPN, and ACh levels were measured following saline and then mecamylamine administration. In Study 2, separate groups of naïve control or nicotine-treated rats received saline or mecamylamine and physical signs and anxiety-like behavior were assessed using elevated plus maze (EPM) procedures. The IPN was then dissected and mRNA levels were assessed using RT-qPCR methods. Nicotine treatment increased ACh levels to a larger extent in females than males. Nicotine withdrawal produced a similar increase in physical signs; however, females displayed greater anxiety-like behavior than males. In females, gene expression of α5 increased following nicotine treatment and withdrawal. In males, α7 increased following nicotine treatment and α2 and α3 increased during nicotine withdrawal. Both females and males displayed an increase in ß3 and ß4 during nicotine withdrawal. In females, anxiety-like behavior was correlated with α4, α5, and ß2 gene expression in the IPN. These results suggest that sex differences in withdrawal are modulated via cholinergic systems in the IPN.

Amino acid modulation of dopamine in the nucleus accumbens mediates sex differences in nicotine withdrawal.

The aversive effect of nicotine withdrawal is greater in female versus male rats, and we postulate that this sex difference is mediated in the nucleus accumbens (NAc). Nicotine withdrawal induces decreases in NAc dopamine and increases in acetylcholine (ACh) levels in male rats. To our knowledge, these neurochemical markers of nicotine withdrawal have not been compared in female versus male rats. Given the role of amino acids in modulating NAc dopaminergic and cholinergic transmission, concomitant measures of gamma-aminobutyric acid (GABA) and glutamate levels were also compared across sex. Rats received continuous nicotine exposure for 14 days, and then NAc dialysate was collected during baseline and following administration of the nicotinic receptor antagonist mecamylamine to precipitate withdrawal. Chronic nicotine exposure was associated with larger increases in baseline dopamine, GABA and glutamate levels in the NAc of female versus male rats, whereas baseline ACh was only increased in male rats. During withdrawal, both sexes displayed equivalent increases in NAc ACh levels. As expected, male rats displayed decreases in dopamine, coupled with increases in GABA and decreases in glutamate levels, suggesting the possibility of increased inhibitory tone in the NAc during withdrawal. Relative to males, female rats displayed larger decreases in NAc dopamine and related increases in GABAergic transmission. As female rats also showed elevated glutamate levels that persist during withdrawal, it is suggested that sex differences may arise from increased glutamatergic drive of inhibitory tone in the NAc. The findings provide a potential mechanism whereby the aversive effects of nicotine withdrawal are enhanced in female rats.

Both nicotine reward and withdrawal are enhanced in a rodent model of diabetes.

RATIONALE: It is presently unclear whether diabetic rats experience greater rewarding effects of nicotine and/or negative affective states produced by nicotine withdrawal. OBJECTIVE: The present study utilized a rodent model of diabetes to examine the rewarding effects of nicotine and negative affective states and physical signs produced by withdrawal. METHODS: Separate groups of rats received systemic administration of either vehicle or streptozotocin (STZ), which destroys insulin-producing beta cells in the pancreas and elevates glucose levels. Place conditioning procedures were utilized to compare the rewarding effects of nicotine (conditioned place preference; CPP) and negative affective states produced by withdrawal (conditioned place aversion; CPA) in vehicle- and STZ-treated rats. CPA and physical signs of withdrawal were compared after administration of the nicotinic receptor antagonist mecamylamine to precipitate withdrawal in nicotine-dependent rats. A subsequent study utilized elevated plus maze (EPM) procedures to compare anxiety-like behavior produced by nicotine withdrawal in vehicle- and STZ-treated rats. RESULTS: STZ-treated rats displayed greater rewarding effects of nicotine and a larger magnitude of aversive effects and physical signs produced by withdrawal as compared to vehicle-treated controls. STZ-treated rats also displayed higher levels of anxiety-like behavior on the EPM during nicotine withdrawal as compared to controls. CONCLUSION: The finding that both nicotine reward and withdrawal are enhanced in a rodent model of diabetes implies that the strong behavioral effects of nicotine promote tobacco use in persons with metabolic disorders, such as diabetes.

Nicotine withdrawal increases stress-associated genes in the nucleus accumbens of female rats in a hormone-dependent manner.

INTRODUCTION: Previous work led to our hypothesis that sex differences produced by nicotine withdrawal are modulated by stress and dopamine systems in the nucleus accumbens (NAcc). We investigated our hypothesis by studying intact females to determine whether the mechanisms that promote withdrawal are ovarian-hormone mediated. METHODS: Female rats were ovariectomized (OVX) or received sham surgery (intact) on postnatal day (PND 45-46). On PND 60, they received sham surgery (controls) or were prepared with nicotine pumps. Fourteen days later, half of the rats had their pumps removed (nicotine withdrawal) and the other half received sham surgery (nicotine exposure). Twenty-four hours later, the rats were tested for anxiety-like behavior using the elevated plus maze and light/dark transfer procedures. The NAcc was then dissected for analysis of several genes related to stress (CRF, UCN, CRF-R1, CRF-R2, CRF-BP, and Arrb2) or receptors for dopamine (Drd1 and Drd2) and estradiol (Esr2). RESULTS: During withdrawal, intact females displayed an increase in anxiety-like behavior in both tests and CRF, UCN, and Drd1 gene expression. During nicotine exposure, intact females displayed a decrease in CRF-R1, CRF-R2, Drd3, and Esr2 gene expression and an increase in CRF-BP. This pattern of results was absent in OVX females. CONCLUSIONS: Nicotine withdrawal produced an increase in anxiety-like behavior and stress-associated genes in intact females that is distinct from changes produced by nicotine exposure. The latter effects were absent in OVX females, suggesting that stress produced by withdrawal is ovarian-hormone mediated. These findings have important implications towards understanding tobacco use liability among females.

Cholinergic transmission during nicotine withdrawal is influenced by age and pre-exposure to nicotine: implications for teenage smoking.

Adolescence is a unique period of development characterized by enhanced tobacco use and long-term vulnerability to neurochemical changes produced by adolescent nicotine exposure. In order to understand the underlying mechanisms that contribute to developmental differences in tobacco use, this study compared changes in cholinergic transmission during nicotine exposure and withdrawal in naïve adult rats compared to (1) adolescent rats and (2) adult rats that were pre-exposed to nicotine during adolescence. The first study compared extracellular levels of acetylcholine (ACh) in the nucleus accumbens (NAc) during nicotine exposure and precipitated withdrawal using microdialysis procedures. Adolescent (postnatal day, PND, 28-42) and adult rats (PND60-74) were prepared with osmotic pumps that delivered nicotine for 14 days (adolescents 4.7 mg/kg/day; adults 3.2 mg/kg/day; expressed as base). Another group of adults was exposed to nicotine during adolescence and then again in adulthood (pre-exposed adults) using similar methods. Control rats received a sham surgery. Following 13 days of nicotine exposure, the rats were implanted with microdialysis probes in the NAc. The following day, dialysis samples were collected during baseline and following systemic administration of the nicotinic receptor antagonist mecamylamine (1.5 and 3.0 mg/kg, i.p.) to precipitate withdrawal. A second study compared various metabolic differences in cholinergic transmission using the same treatment procedures as the first study. Following 14 days of nicotine exposure, the NAc was dissected and acetylcholinesterase (AChE) activity was compared across groups. In order to examine potential group differences in nicotine metabolism, blood plasma levels of cotinine (a nicotine metabolite) were also compared following 14 days of nicotine exposure. The results from the first study revealed that nicotine exposure increased baseline ACh levels to a greater extent in adolescent versus adult rats. During nicotine withdrawal, ACh levels in the NAc were increased in a similar manner in adolescent versus adult rats. However, the increase in ACh that was observed in adult rats experiencing nicotine withdrawal was blunted in pre-exposed adults. These neurochemical effects do not appear to be related to nicotine metabolism, as plasma cotinine levels were similar across all groups. The second study revealed that nicotine exposure increased AChE activity in the NAc to a greater extent in adolescent versus adult rats. There was no difference in AChE activity in pre-exposed versus naïve adult rats. In conclusion, our results suggest that nicotine exposure during adolescence enhances baseline ACh in the NAc. However, the finding that ACh levels were similar during withdrawal in adolescent and adult rats suggests that the enhanced vulnerability to tobacco use during adolescence is not related to age differences in withdrawal-induced increases in cholinergic transmission. Our results also suggest that exposure to nicotine during adolescence suppresses withdrawal-induced increases in cholinergic responses during withdrawal. Taken together, this report illustrates important short- and long-term changes within cholinergic systems that may contribute to the enhanced susceptibility to tobacco use during adolescence.

Behavioral, Biochemical, and Molecular Indices of Stress are Enhanced in Female Versus Male Rats Experiencing Nicotine Withdrawal.

Stress is a major factor that promotes tobacco use and relapse during withdrawal. Although women are more vulnerable to tobacco use than men, the manner in which stress contributes to tobacco use in women versus men is unclear. Thus, the goal of this study was to compare behavioral and biological indices of stress in male and female rats during nicotine withdrawal. Since the effects of nicotine withdrawal are age-dependent, this study also included adolescent rats. An initial study was conducted to provide comparable nicotine doses across age and sex during nicotine exposure and withdrawal. Rats received sham surgery or an osmotic pump that delivered nicotine. After 14 days of nicotine, the pumps were removed and controls received a sham surgery. Twenty-four hours later, anxiety-like behavior and plasma corticosterone were assessed. The nucleus accumbens (NAcc), amygdala, and hypothalamus were examined for changes in corticotropin-releasing factor (CRF) gene expression. In order to differentiate the effects of nicotine withdrawal from exposure to nicotine, a cohort of rats did not have their pumps removed. The major finding is that during nicotine withdrawal, adult females display higher levels of anxiety-like behavior, plasma corticosterone, and CRF mRNA expression in the NAcc relative to adult males. However, during nicotine exposure, adult males exhibited higher levels of corticosterone and CRF mRNA in the amygdala relative to females. Adolescents displayed less nicotine withdrawal than adults. Moreover, adolescent males displayed an increase in anxiety-like behavior and an up-regulation of CRF mRNA in the amygdala during nicotine exposure and withdrawal. These findings are likely related to stress produced by the high doses of nicotine that were administered to adolescents to produce equivalent levels of cotinine as adults. In conclusion, these findings suggest that intense stress produced by nicotine withdrawal may contribute to tobacco use in women.

Health-related conditions and depression in elderly mexican american and non-Hispanic white residents of a United States-Mexico border county: moderating effects of educational attainment.

We investigated the prevalence of "high" levels of depressive symptomatology and 13 health-related medical conditions in elderly Mexican American (MA) and non-Hispanic white (NHW) residents of El Paso County, Texas. We analyzed the extent to which depressive symptoms in this population are associated with these conditions. Elderly MA residents possessed a higher prevalence of current depression, a relatively unique health-related condition profile, and were more likely to experience a set of conditions that impede participation in daily life-conditions that we found to be strongly associated with high depressive symptomatology in the elderly. After adjusting for educational attainment, using multiple regression analyses, depression was not associated with ethnicity and only six of the health related conditions showed significant differences between MA and NHW subjects. We believe these results provide an important insight into the mechanism of health-related conditions and depressive symptomatology in a large sample of elderly MAs; and how conditions typically attributed to MA ethnicity may in actuality be an artifact of socioeconomic status variables such as educational-attainment.

Negative affect heightens opiate withdrawal-induced hyperalgesia in heroin dependent individuals.

This study examined the effect of emotion on opiate withdrawal induced hyperalgesia to determine whether emotional states modulate the magnitude of hyperalgesia. One hundred Hispanic men were recruited into one of three groups: heroin withdrawal, long-term heroin abstinence, and control. Participants were presented with pictures to induce neutral, positive, and negative emotional states. Affective valence, arousal, pain threshold, and tolerance to ischemic pain were measured. When pain threshold and tolerance were compared, the withdrawal group displayed significant heightened pain sensitivity when negative affect was induced. The authors also found that former heroin addicts showed heightened pain sensitivity following months of abstinence.

Chronic restraint stress during early Theiler's virus infection exacerbates the subsequent demyelinating disease in SJL mice: II. CNS disease severity.

Theiler's murine encephalomyelitis virus (TMEV) infection is a well-characterized model of multiple sclerosis (MS). Previous research has shown that chronic restraint stress (RS) during early TMEV infection exacerbates behavioral signs of the disease. The present data suggest that RS-induced increases in CNS inflammation, demyelination, and axonal degeneration may underlie this exacerbation. In addition, we report that males exhibit greater CNS inflammation and higher numbers of demyelinating lesions while females show greater susceptibility to RS-induced exacerbation. These findings indicate that RS during early TMEV infection increases CNS lesion formation during the late phase and suggest that the effects of RS are sex-dependent.

Spinal glia modulate both adaptive and pathological processes.

Recent research indicates that glial cells control complex functions within the nervous system. For example, it has been shown that glial cells contribute to the development of pathological pain, the process of long-term potentiation, and the formation of memories. These data suggest that glial cell activation exerts both adaptive and pathological effects within the CNS. To extend this line of work, the present study investigated the role of glia in spinal learning and spinal learning deficits using the spinal instrumental learning paradigm. In this paradigm rats are transected at the second thoracic vertebra (T2) and given shock to one hind limb whenever the limb is extended (controllable shock). Over time these subjects exhibit an increase in flexion duration that reduces net shock exposure. However, when spinalized rats are exposed to uncontrollable shock or inflammatory stimuli prior to testing with controllable shock, they exhibit a learning deficit. To examine the role of glial in this paradigm, spinal glial cells were pharmacologically inhibited through the use of fluorocitrate. Our results indicate that glia are involved in the acquisition, but not maintenance, of spinal learning. Furthermore, the data indicate that glial cells are involved in the development of both shock and inflammation-induced learning deficits. These findings are consistent with prior research indicating that glial cells are involved in both adaptive and pathological processes within the spinal cord.

In utero methanesulfonyl fluoride differentially affects learning and maze performance in the absence of long-lasting cholinergic changes in the adult rat.

There is increasing evidence that acetylcholinesterase (AChE) may have various specific developmental roles in brain development. Nevertheless, specific effects of AChE inhibition during early brain development have not been adequately described. Therefore, methanesulfonyl fluoride (MSF), an irreversible AChE inhibitor that shows high selectivity for the CNS was used to produce AChE inhibition in utero to study subsequent adult behaviors, sleep, and cholinergic markers. Rats exposed to MSF in utero showed a deficit in spatial learning tasks using appetitive motivation but, surprisingly, they performed equally well or better than controls when aversive motivation was used. One hypothesis was that MSF treatment in utero affected the response to stress. Tests of anxiety however showed no differences in basal levels of anxiety. Studies of sleep behavior, however, indicated a higher level of REM sleep which is only seen during the light phase of male rats exposed to MSF in utero as compared to controls. No differences in cholinergic markers in the brains of adults were found except that females exposed to MSF in utero had a higher level of ChAT activity in the synaptosomal fraction of the hippocampus. Even so, whether cholinergic alterations accompany the in utero MSF exposure remains to be determined. The failure to find widespread changes in cholinergic markers in the adult brains suggests changes in behaviors should be further investigated by testing the participation of postsynaptic mechanisms, measuring of cholinergic markers during earlier development periods and the possible participation of other neurotransmitter systems to clearly reveal the role of the cholinergic system following in utero MSF exposure.