Prenatal ethanol effects on reward efficacy for adult mice are gestation stage specific

Effects of vigabatrin, an irreversible GABA transaminase inhibitor, on ethanol reinforcement and ethanol discriminative stimuli in mice

We tested the hypothesis that the irreversible γ-amino butyric acid transaminase inhibitor, γ-vinyl γ-amino butyric acid [vigabatrin (VGB)], would reduce ethanol reinforcement and enhance the discriminative-stimulus effect of ethanol, effectively reducing ethanol intake. The present studies used adult C57BL/6J (B6) mice in well-established operant, two-bottle choice consumption, locomotor activity, and ethanol discrimination procedures to comprehensively examine the effects of VGB on ethanol-supported behaviors. VGB dose-dependently reduced operant responding for ethanol and ethanol consumption for long periods of time. Importantly, a low dose (200 mg/kg) of VGB was selective for reducing ethanol responding without altering the intake of food or water reinforcement. Higher VGB doses (>200mg/kg) reduced ethanol intake, but also significantly increased water consumption and, more modestly, increased food consumption. Although not affecting locomotor activity on its own, VGB interacted with ethanol to reduce the stimulatory effects of ethanol on locomotion. Finally, VGB (200 mg/kg) significantly enhanced the discriminative-stimulus effects of ethanol as evidenced by significant leftward and upward shifts in ethanol generalization curves. Interestingly, VGB treatment was associated with slight increases in blood ethanol concentrations. The reduction in ethanol intake by VGB appears to be related to the ability of VGB to potentiate the pharmacological effects of ethanol.

Characterizing the behavioral effects of nerve agent-induced seizure activity in rats: increased startle reactivity and perseverative behavior

The development and deployment of next-generation therapeutics to protect military and civilian personnel against chemical warfare nerve agent threats require the establishment and validation of animal models. The purpose of the present investigation was to characterize the behavioral consequences of soman (GD)-induced seizure activity using a series of behavioral assessments. Male Sprague-Dawley rats (n=24), implanted with a transmitter for telemetric recording of encephalographic signals, were administered either saline or 1.0 LD₅₀ GD (110 μg/kg, sc) followed by treatment with a combination of atropine sulfate (2 mg/kg, im) and the oxime HI-6 (93.6 mg/kg, im) at 1 min post-exposure. Seizure activity was allowed to continue for 30 min before administration of the anticonvulsant diazepam (10 mg/kg, sc). The animals that received GD and experienced seizure activity had elevated startle responses to both 100- and 120-dB startle stimuli compared to control animals. The GD-exposed animals that had seizure activity also exhibited diminished prepulse inhibition in response to 120-dB startle stimuli, indicating altered sensorimotor gating. The animals were subsequently evaluated for the acquisition of lever pressing using an autoshaping procedure. Animals that experienced seizure activity engaged in more goal-directed (i.e., head entries into the food trough) behavior than did control animals. There were, however, no differences between groups in the number of lever presses made during 15 sessions of autoshaping. Finally, the animals were evaluated for the development of fixed-ratio (FR) schedule performance. Animals that experienced GD-induced seizure activity engaged in perseverative food trough-directed behaviors. There were few differences between groups on other measures of FR schedule-controlled behavior. It is concluded that the GD-induced seizure activity increased startle reactivity and engendered perseverative responding and that these measures are useful for assessing the long-term effects of GD exposure in rats.

Methylmercury and nutrition: adult effects of fetal exposure in experimental models

Human exposure to the life-span developmental neurotoxicant, methylmercury (MeHg), is primarily via the consumption of fish or marine mammals. Fish are also excellent sources of important nutrients, including selenium and n-3 polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA). Laboratory models of developmental MeHg exposure can be employed to assess the roles of nutrients and MeHg and to identify potential mechanisms of action if the appropriate exposure measures are used. When maternal exposure is protracted, relationships between daily intake and brain mercury are consistent and orderly across species, even when large differences in blood:brain ratios exist. It is well established that low-level developmental MeHg produces sensory deficits. Recent studies also show that perseveration in reversal-learning tasks occurs after gestational exposures that produce low micromolar concentrations in the brain. A no-effect level has not been identified for this effect. These exposures do not affect the acquisition or performance of discrimination learning, set shifting (extradimensional shift), or memory. Reversal-learning deficits may be related to enhanced impact of reinforcers as measured using progressive ratio reinforcement schedules, an effect that could result in perseveration. Also reported is enhanced sensitivity to dopamine reuptake inhibitors and diminished sensitivity to pentobarbital, a GABA(A) agonist. Diets rich in PUFAs or selenium do not protect against MeHg's effects on reversal learning but, by themselves, may diminish variability in performance, enhance attention or psychomotor function and may confer some protection against age-related deficits in these areas. It is hypothesized that altered reward processing, dopamine and GABAergic neurotransmitter systems, and cortical regions associated with choice and perseveration are especially sensitive to developmental MeHg at low exposure levels. Human testing for MeHg's neurotoxicity should emphasize these behavioral domains.

Alcohol exposure during development alters social recognition and social communication in rats

The present study examined the effects of postnatal alcohol exposure via gastric intubation on social communication of diet preference and social recognition. Rats were placed in one of three treatment groups. All treatments occurred from postnatal day (PD) 2 through 10 and Experiments 1 and 2 were conducted when the rats reached 60 and 100 days of age, respectively. Alcohol-exposed pups received a 3.0 g/kg dose of ethanol in milk solution that was delivered by insertion of PE-10 tubing down the esophagus daily from PD 2 through 10. Intubated control animals underwent intubation without ethanol or milk. Nontreated control pups were weighted daily. In Experiment 1, a nonexperimental rat was initially given access to lab chow mixed with a spice and then housed with an experimental rat for 30 min. The experimental rat was subsequently given access to two diets--one that the nonexperimental rat had consumed and a novel diet. It was found that the alcohol-exposed females consumed a greater percent of the communicated diet than the control females. In Experiment 2, the experimental rats were first exposed to a juvenile for 5 min and then exposed to the same juvenile after a delay of 30 or 90 min. Investigation time was recorded in both sessions and a reduction of investigation time in the second session is an indicator of social recognition memory. Alcohol-exposed rats of both sexes had poorer memory of a juvenile than both control groups after a 90-min delay. Together, these data indicate that basic components of social behavior may be altered by alcohol exposure during development.

Teratogenic actions of ethanol in the mouse: a minireview

The deleterious effects of prenatal ethanol exposure have been extensively documented in clinical and experimental studies. This paper provides an overview of work conducted with mice to examine the myriad of adverse consequences that result from embryonic/fetal exposure to ethanol. All of the hallmark features of the clinical fetal alcohol syndrome have been demonstrated in mice, including prenatal and postnatal growth retardation, structural malformations and behavioral abnormalities associated with central nervous system dysfunction. As expected, the severity and profile of effects is related to both dosage level and timing of exposure. In addition, these effects have been demonstrated following acute and chronic exposure, with a variety of routes of administration employed. Furthermore, a number of strains have been used in these studies and the variant response (susceptibility) to the teratogenic actions of ethanol exhibited among different mouse strains support the notion that genetic factors govern, at least in part, vulnerability to these effects of ethanol. More recent studies using mouse models have focused on examining potential mechanisms underlying the full spectrum of ethanol's teratogenic actions.

Effects of prenatal ethanol exposure on dopamine systems in C57BL/6J mice

Young rats prenatally exposed to ethanol exhibit heightened responses to dopaminergie (DA) drugs, altered brain concentrations of dopamine, and its metabolite dihydroxyphenylacetic acid (DOPAC), and transient reductions in DA receptor binding. Adult mice exposed to ethanol prenatally also exhibit increased responses to DA drugs; however, brain concentrations of DA and DOPAC are unaltered. The effects of prenatal ethanol exposure on DA or DOPAC concentrations in young mice or on DA receptor binding in mice of any age are unknown. Therefore, to determine if the different effects of prenatal ethanol exposure on rats and mice are due to age at time of testing or species, we determined its effects on DA concentrations and turnover in young mice under conditions previously reported for adult offspring and on DA D1 and D2 receptor binding in both young and adult offspring. Consistent with our previous report for adult offspring, prenatal ethanol exposure did not alter DA concentrations or turnover. The treatment did, however, diminish periadolescent growth as previously reported and produced a transient increase in DA D1, but not DA D2 receptor binding. DA receptor binding was not altered in adult offspring. Although unrelated to prenatal ethanol exposure, the sexes differed on all of the DA measures. Combined with previous reports, the present study suggests that species rather than age is more likely to account for the different effects of prenatal ethanol exposure on DA systems, and that sex differences in DA systems should be further examined.

Perinatal maternal ethanol effects on pregnant mice and on offspring viability and growth: influences of exposure time and weaning diet

C57BL/6 mice were maintained on liquid diets containing 27.5% ethanol-derived calories beginning on gestational day 12. For one group, the liquid diet was replaced with laboratory chow on the morning of gestational day 18, approximately 24 hr before delivery. For a second group, the diet was continued for 7 days postnatally. Two additional groups were pair-fed isocaloric sucrose diets, and a final group was maintained on normal laboratory chow. The mice consumed sufficient amounts of diet to provide near 30 g ethanol/kg/day during pregnancy and slightly greater amounts during the first postpartum week. The ethanol diet produced no maternal deaths and did not alter weight gain during gestational days 12-17 of pregnancy. The results confirmed previous reports that dietary ethanol exposure under conditions that have rather minor effects on the pregnant mouse can substantially affect the fetus. As previously reported, when exposure was terminated 24 hr before delivery, neonatal mortality was elevated by approximately 30%, but birth weight was not altered. When the diet was extended into the lactation period, mortality was delayed but not reduced, possibly by reducing the severity of ethanol withdrawal. Birthweight was reduced by 10% when exposure continued until birth, suggesting that low birthweights for fetal ethanol-exposed (FEE) mice can be eliminated by terminating exposure approximately 24 hr before delivery. As in previous reports, FEE mice with normal birthweights had an attenuated preadolescent growth spurt, suggesting that low birthweights and attenuated postnatal growth are likely mediated by different mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Prenatal ethanol effects and dopamine systems of adult C57 male mice

Behavioral, pharmacological, and neurochemical studies indicate that prenatal ethanol exposure can alter dopamine (DA) systems of developing rats. In addition, some of the behavioral changes described for prenatal-ethanol-exposed rats and mice (e.g., reduced responding for food and other rewards) as well as their response to various psychoactive drugs (e.g., amphetamines, methylphenidate, haloperidol) suggest that the DA system changes might extend into adulthood. Neurochemical studies on the effects of prenatal ethanol on DA systems of adults have not been reported for either species. The present study provides a neurochemical assessment of prenatal ethanol effects on DA systems of fully mature mice. Compared to chow and sucrose controls, adult offspring of mice fed a diet containing 25% ethanol derived calories had preadolescent growth deficits as observed in previous studies which also showed long-term behavioral deficits. Prenatal ethanol exposure in the present study, however, did not alter the concentration of DA or dihydroxyphenylacetic acid (DOPAC) nor the progressive decline in the concentration of these compounds in either striatum or nucleus accumbens of mature mice at intervals after synthesis inhibition by alpha-methyl-DL-p-tyrosine. Thus, the present study provides no neurochemical confirmation of altered DA systems resulting from prenatal ethanol exposure under conditions previously observed to alter adult behavior.