Region-dependent alterations in glutamate and GABA measured by high-resolution magnetic resonance spectroscopy following acute binge inhalation of toluene in juvenile rats.

Little is known about the neurochemical effects accompanying the high-concentration inhalant exposures characteristic of binge solvent abuse. In adult animals, prior studies with other patterns of exposure indicate that toluene, a commonly abused household and industrial solvent, has significant effects on the glutamatergic and GABAergic neurotransmitter systems and on other neurotransmitter systems as well. In the current investigation, high-resolution "magic angle" spinning proton magnetic resonance spectroscopy (HR-MAS (1)H-MRS) was used to assess the effect of acute binge toluene inhalation on regional brain concentrations of various neurochemicals including glutamate (GLU), GABA, and glutamine (GLN) in juvenile male and female rats. Acute toluene (8000 ppm or 12,000 ppm) significantly reduced levels of hippocampal GABA (-12%) and GLU (-8%), and the GLU/GLN ratio, an index of glutamatergic tone, was significantly reduced (-22%) in the dorsal anterior striatum, driven largely by a 28% increase in GLN. Significant increases in alanine and lactate in several brain regions after acute toluene may be indicative of altered oxygen-dependent metabolism associated with the inhalation of higher concentrations of toluene (e.g., >5000 ppm). Other components of the MR-visible neurochemical profile, such as N-acetylaspartate (NAA), myo-inositol, creatine, and various choline containing compounds, were unchanged by acute toluene. The results are consistent with the notion that binge toluene exposure affects juvenile neurochemistry in systems mediating the rewarding and emotional aspects of substance abuse. Moreover the results provide a framework to understand further (1)H-MRS studies in clinical populations.

Prenatal toluene exposure impairs performance in the Morris Water Maze in adolescent rats.

Volatile organic solvent abuse continues to be a worldwide health problem, including the neurobehavioral teratogenic sequelae of toluene abuse during pregnancy. Although abuse levels of prenatal toluene exposure can lead to a Fetal Solvent Syndrome, there is little research examining these effects on memory. Consumption of toluene can have detrimental effects on the developing hippocampus which could lead to specific spatial learning and memory deficits. This study used a rat model to determine how prenatal exposure to abuse levels of toluene would affect performance in a spatial learning and memory task, the Morris Water Maze (MWM). Pregnant Sprague-Dawley rats were exposed to 0, 8000 or 12,000ppm (ppm) of toluene for 15min twice daily from gestation day 8 (GD8) through GD20. Male and female offspring (N=104) were observed in the MWM for 5days beginning on postnatal day (PN) 28 and again on PN44. While prenatal toluene-exposed animals did not differ in initial acquisition in the MWM, rats prenatally exposed to 12,000ppm toluene displayed performance deficits during a probe trial and in reversal learning on PN44. Overall, this study indicates that prenatal exposure to repeated inhaled abuse patterns of high concentrations of toluene can impair spatial memory function that persists into adolescence.

Effects of gestational alcohol exposure on the fatty acid composition of umbilical cord serum in humans.

This study examined the effects of maternal periconceptional alcohol intake on polyunsaturated fatty acid (PUFA) concentrations in human neonates. The area percentage of each fatty acid in cord blood serum from 12 infants born to control women (who consumed <2 mL absolute ethanol/d) was compared with that of 9 infants born to women whose periconceptional alcohol intake averaged > or = 30mL absolute ethanol/d. Periconceptional alcohol use was associated with a 30% increase in the proportion of docosahexaenoic acid (22:6n-3) in cord blood (3.0% of total lipid in control infants compared with 3.9% in alcohol-exposed infants; P < 0.01). The rise in the proportion of 22:6n-3 was responsible for increases in the ratio of n-3 to n-6 fatty acids and the ratio of long-chain n-3 to n-6 fatty acids (P < 0.055). Examination of the lipid-class fatty acid profile indicated that serum lipid alterations were localized to the cholesterol esters; 22:6n-3 in the cholesterol esters of alcohol-exposed infants increased 54% (P < 0.011) and arachidonic acid increased 55% (P < 0. 005). The relative fatty acyl composition of maternal serum showed a significant increase in 18:0 fatty acids in the alcohol-exposed group (25%, P < 0.005) but there were no changes in the other fatty acids. The increase in the proportion of 22:6n-3 was unexpected but is consistent with the hypothesis that this essential lipid may be conserved selectively. These results imply that the lifelong neurobehavioral and sensory dysfunction in fetal alcohol syndrome and other alcohol-related neurodevelopmental disorders may be due in part to PUFA dysregulation.

A parametric study of the behavioral effects of phencyclidine in adult cats.

Five adult cats received four doses of phencyclidine to determine the behavioral effects of this compound. On alternate weeks the animals received control injections of saline vehicle. Dose-dependent behavioral changes occurred in three general categories (posture, locomotor activity and stereotyped head movements). In small doses (0.1 and 0.5 mg/kg), major postural effects consisted of head and body tremors and loss of hindlimb support. In larger doses (1.0 and 2.0 mg/kg), the postural effects occurred more rapidly and became more severe as animals lost both forelimb and hindlimb support and ultimately became immobile. Small doses of phencyclidine produced decreases in locomotor activity, followed by increases. Larger doses produced initial increases in activity. Increases in head movement stereotypies were produced by all doses of phencyclidine.

Changes in dopamine and DOPAC following systemic administration of apomorphine and 3,4-dihydroxyphenylamino-2-imidazoline (DPI) in rats.

Rats were injected systemically with either saline, apomorphine, or one of four doses of DPI (3,4-dihydroxyphenylamino-2-imidazoline) and the levels of dopamine and DOPAC determined in the nucleus accumbens and the caudate regions. DPI reduced dopamine and DOPAC levels in the nucleus accumbens, while apomorphine did not. On the other hand, apomorphine reduced the levels of dopamine and DOPAC in the caudate but not the nucleus accumbens. DPI largely was without effect in the caudate. The results are discussed in terms of possible specificity of the two dopamine agonists in the two forebrain regions.

Differentiation of basal ganglia dopaminergic involvement in behavior after hippocampectomy.

Large bilateral aspiration lesions of the hippocampus in rats lead to a variety of changes in spontaneous behavior measured in an open field/hole board, relative to sham and neocortically lesioned controls. These changes include increased locomotion, and decreased grooming frequency and rearing bout duration. When animals were injected with the dopamine (DA) agonist 3,4-dihydroxyphenylamino-2-imidazoline (DPI: 0.5, 1.0 and 5.0 microgram) into the nucleus accumbens one week after surgery, the behavior of hippocampally lesioned rats was restored to levels not different from control lesioned rats. Haloperidol injections (0.05, 0.1 and 0.5 microgram) into the caudate nucleus were not able to do this. Further, DPI injected into the caudate month after surgery was also able to attenuate some of the effects of hippocampal damage. On the other hand, haloperidol injections into the nucleus accumbens did not influence behavior. The results are interpreted in terms of hippocampal lesion-induced alteration of a balance in basal ganglia DA systems, indicated by modified response to pharmacological intervention and which mediate the behavioral effects of the lesion.

Behavioral effects of D-amphetamine in developing cats.

The development of the behavioral effects of amphetamine was assessed in kittens of 1-53 days of age. Amphetamine-induced increases in locomotion occurred when animals were beyond 35 days of age. Stereotypic behavior was induced at all ages tested but the predominant type of stereotypy was age-related. From 1 to 14 days amphetamine induced licking. Pendular head movements occurred when animals were under 35 days. At 14 days of age darting, a response consisting of rapid pacing and turning began to occur. Tracking, a series of horizontal and vertical head movements also began to occur after 14 days. The adult response of vertical and horizontal head movements became most prominent after 35 days.

The immobility response in the forced swim test: paradoxical effect of imipramine.

Rats immersed in a modified version of the forced swim test in which they are unable to touch the bottom of the cylinder with their feet while keeping their noses above water, initially paddle vigorously but eventually become relatively immobile. In the present study, we show that chronic treatment with imipramine and alprazolam increases rather than decreases the immobility response of rats in this test, whereas chronic treatment with propranolol is less effective. The results of this study indicate that the interpretation of the immobility response as 'behavioral despair', which is based on the response to the antidepressant drugs such as imipramine, needs to be reevaluated.

Cholinergic maturation and SCH 23390-induced catalepsy in the male rat pup.

The cataleptogenic effects of the selective dopamine D1 receptor antagonist, SCH 23390, increased between 13 and 17 days of age in male pups. Seventeen- and 21-day-old pups showed equivalent catalepsy. Scopolamine blocked SCH 23390-induced catalepsy in 21-day-old pups but had little effect in 13-day-old pups. The development and cholinergic sensitivity of SCH 23390-induced catalepsy are similar to those seen after D2 or mixed D1/D2 receptor blockade. Cholinergic maturation appears to be an important component in the development of adult-like catalepsy, and the nature of a D1-acetylcholine interaction mediating catalepsy remains to be determined.

Reversal of alcohol's effects on neurite extension and on neuronal GAP43/B50, N-myc, and c-myc protein levels by retinoic acid.

Alcohol teratogenesis may be due in part to inhibition of neuronal differentiation by ethanol. We showed previously that alcohol decreased neuronal differentiation (neurite extension) and increased N-myc and c-myc neuronal protein levels. Since Growth-Associated Protein 43 (GAP43/B50) levels must increase for neurons to differentiate, alcohol may decrease GAP43/B50. Alcohol dose-dependently (0-0.5%) decreased GAP43/B50 protein levels by up to 92% in immature LA-N-5 cells. Five nM retinoic acid alone induced differentiation and increased GAP43/B50 levels to 230% of control. These retinoic acid-induced increases in GAP43/B50 and neurite outgrowth, and decreases in N-myc and c-myc, were reversed dose-dependently by alcohol (0-0.5%). Conversely, the adverse effects of 0.25% alcohol on neurite extension, GAP43/B50, N-myc, and c-myc were prevented by 15 and 45 nM retinoic acid. These results suggest that inhibition of neuronal differentiation by alcohol and prevention of such effects by retinoic acid are related to changes in GAP43/B50, N-myc and c-myc.

The time course of excessive grooming after neuropeptide administration.

In this paper we review the temporal pattern of excessive grooming in the hour or so following the central injection of ACTH1-24 in the rat. Changes in the grooming pattern after specific neuropharmacological manipulations of dopaminergic and opiate-related systems are presented which indicate a differential sensitivity of the grooming responses at different times after injection. The grooming affected by dopaminergic antagonists and opiate agonists and antagonists occurs in the last 30 min of the observation period while that found earlier is unaffected. It is also the grooming in this last 30 min of the observation period term tolerance to central administration of ACTH1-24. In contrast lesions of the central nervous system that affect excessive grooming, i.e., the substantia nigra and the hippocampus, reduce grooming throughout the observation period. The present analysis has provided evidence for dopamine/opiate insensitive and sensitive systems in excessive grooming, and thus temporal aspects are of extreme importance to the understanding of central neuropeptide influences on behavior.

Dopamine depletion in nucleus accumbens reduces ACTH1-24-induced excessive grooming.

Animals were pretreated with 6-OHDA or ascorbate vehicle injected into the nucleus accumbens and tested 10 days later for excessive grooming induced by intracerebroventricular injection of ACTH1-24. The animals pretreated with 6-OHDA showed a significant decrease in excessive grooming produced by the neuropeptide and this reduction was seen only in the last 30 minutes of a 60-min test session. The results suggest an interaction of ACTH with dopamine systems on the onset and maintenance of excessive grooming.

Effects of chronic forced swimming and exposure to alarm substance: physiological and behavioral consequences.

Rats tested for 7 consecutive days in the forced swim test in fresh water were more immobile than those tested in soiled water on all days. Animals in both water conditions increased their immobility times slightly over days, but animals tested in soiled water, which presumably contained an alarm substance, never attained the immobility times of those tested in fresh water. When animals were switched between fresh and soiled water, they behaved exactly like animals in the water condition to which they were switched. Prior inescapable forced swimming in either water condition affected subsequent escape in a Morris water maze, but more so for animals tested only in fresh water. A second study corroborated the escape results. Serum corticosterone and relative adrenal weights were increased as a result of forced swimming but escape performance differences could not be attributed to differences in the stress-provoking consequences of the two water conditions.

What research with animals is telling us about alcohol-related neurodevelopmental disorder.

The substantial advances in understanding fetal alcohol syndrome over the past 20 years were made in large part because of research with animals. This review illustrates recent progress in animal research by focusing primarily on the central nervous system effects of prenatal alcohol exposure. Current findings suggest further progress in understanding consequences, risk factors, mechanisms, prevention and treatment will depend on continued research with animals.

The effects of Org 2766 on the performance of sham, neocortical, and hippocampal-lesioned rats in a food search task.

The behavioral effects of an ACTH4-9 variant, Org 2766, given for one week postoperatively at a dose of 1 microgram/rat daily, were evaluated in animals given hippocampal, neocortical, or "sham" lesions. After the week during which the injections were given, the animals were tested for 5 days in a food-search task in which food was hidden in two recessed holes in the floor. On the next day the ability of the rats to find food in these same two baited holes was tested in the presence of 14 additional holes that were not baited. On the following day, the animals were tested again, this time with all 16 holes baited. To assess the long-term effects of Org 2766 treatment, the animals were tested once again 2-3 months later in the same apparatus with 16 empty holes. In general, rats with lesions restricted to the neocortex were severely impaired in the task and were unaffected by prior treatment with Org 2766. Animals with hippocampal damage quickly learned the task and were hyperactive. During the test session with 16 baited holes they showed differential behavioral changes suggesting attentional deficits not seen in "sham" operated rats. These deficits were attenuated by prior Org 2766 treatment, whereas the lesion-induced hyperactivity was not. Treatment with Org 2766 impaired all aspects of performance of "sham" operated animals.

Time course of certain behavioral changes after hippocampal damage and their alteration by dopaminergic intervention into nucleus accumbens.

Independent groups of rats with hippocampal, neocortical, or sham lesions were observed 7, 14, or 28 days after surgery in an open field-hole board apparatus and in a smaller circular apparatus. In the circular apparatus, animals were observed after unilateral injection of the dopamine agonist, 3,4-dihydroxyphenylamino-2-imidazoline (DPI) or saline into nucleus accumbens. Behavioral changes in locomotion, exploration and grooming measured in the open field were consistent with those found previously after hippocampal damage, with each behavioral anomaly demonstrating a specific pattern of change after surgery. In general, the injection of DPI into nucleus accumbens produced greater behavioral change in animals with hippocampal damage than in animals with either neocortical or sham lesions. The drug-induced changes in the hippocampally lesioned rats made their behavior more like that of control animals. These results suggest that destruction of the hippocampus may induce alterations in dopaminergic mechanisms in nucleus accumbens which can be modified by appropriate pharmacologic intervention.

Amelioration of fetal alcohol-related neurodevelopmental disorders in rats: exploring pharmacological and environmental treatments.

Fetal alcohol syndrome (FAS) and alcohol-related neurodevelopmental disorders (ARNDs) in children are characterized by life-long compromises in learning, memory, and adaptive responses. Until the advent of effective prevention measures, it will remain necessary to seek ways to treat the life-long neurobehavioral consequences of prenatal alcohol exposure. To date, there are no clinical remedies to recommend for either specific or global fetal alcohol effects. This article reviews our basic research in animal models that assesses the potential of global environmental manipulations or specific psychopharmacological treatments to ameliorate the neurobehavioral effects of prenatal exposure to alcohol. Postweaning environmental enrichment can improve behavioral performance and ameliorate or even eliminate deficits in prenatal alcohol-exposed rats, although there is persistent impairment in neuronal plasticity, as indicated by the failure of hippocampal pyramidal cells to increase dendrite spine density. Behavioral and neural responses to CNS stimulants differ in rats exposed prenatally to alcohol, although it is not clear that these shifts in dose-response curves would predict benefit to children. Although the present results may sound a note of optimism for the development of effective treatment strategies for children with FAS or ARNDs, it is important to consider that application of these findings in rodents may not be straightforward. We also need to know the critical features of specific environments that influence brain development, and the limits of pharmacotherapy, as well as critical periods of exposure. Continued study of the beneficial, ameliorative effects of environmental enrichment, rehabilitative training, and of pharmacological therapies in animal models, will remain a valuable source of information for eventually devising treatments specific for children with FAS and ARNDs.

In utero alcohol and postnatal methylphenidate: locomotion and dopamine receptors.

Prenatal alcohol exposure can cause central nervous system abnormalities and dysfunction referred to as Alcohol-Related Neurodevelopmental Disorder (ARND). Repeated intermittent methylphenidate (Ritalin) was used as a psychopharmacological challenge to reveal functional alterations in dopamine binding sites in rats exposed prenatally to alcohol. Pregnant Long-Evans dams were intubated with 0, 3, or 5 g/kg/day of alcohol from gestational day (GD) 8 to GD20. Adult offspring received repeated intraperitoneal injections of 0, 4, or 8 mg/kg of methylphenidate (MET), and were tested periodically for locomotor activity. Autoradiographic assessment of dopamine D1 and D2 receptors binding were visualized using [3H]SCH 23390 and [3H]raclopride, respectively. Prenatal alcohol did not produce significant dose-dependent effects on adult locomotor activity. Repeated MET injections produced dose-dependent sensitization of locomotor activity in all groups. The 3-g/kg prenatal alcohol group had a significantly decreased number of dopamine D2 binding sites within the dorsal and ventral striatum. This effect was reversed by MET. The neural changes detected in the lower alcohol group may indicate persistent changes within the dopaminergic system due to prenatal alcohol exposure.

Prenatal ethanol exposure: effects on androgen and nonandrogen dependent behaviors and on gonadal development in male rats.

Prenatal exposure to alcohol may impair gonadal and behavioral development in male rats, possibly via reduction of perinatal androgenization. We examined locomotor activity on postnatal day 18 (PND 18), which is not influenced by perinatal androgens and juvenile play and testicular development (testes weight), which are dependent on perinatal androgen exposure, in rats whose dams consumed ethanol during pregnancy. Male offspring of pair-fed and lab chow-fed dams served as controls. Despite reduced anogenital distance at birth, indicating compromised perinatal androgenization, fetal ethanol-exposed males did not exhibit demasculinization of play behavior. Hyperactivity in fetal ethanol-exposed males indicated that the treatment regimen was sufficient to produce behavioral deficits. Testes weight was reduced in both ethanol-exposed and pair-fed offspring, indicating that nutritional deficits associated with maternal ethanol intake may impair normal gonadal development in male rats. The findings suggest that fetal ethanol exposure may influence gonadal development but not necessarily affect a gonadal hormone-dependent behavior.

Maternal risk factors in fetal alcohol syndrome: provocative and permissive influences.

We present an hypothesis integrating epidemiological, clinical case, and basic biomedical research to explain why only relatively few women who drink alcohol during pregnancy give birth to children with alcohol-related birth defects (ARBDs), in particular, Fetal Alcohol Syndrome (FAS). We argue that specific sociobehavioral risk factors, e.g., low socioeconomic status, are permissive for FAS in that they provide the context for increased vulnerability. We illustrate how these permissive factors are related to biological factors, e.g., decreased antioxidant status, which in conjunction with alcohol, provoke FAS/ARBDs in vulnerable fetuses. We propose an integrative heuristic model hypothesizing that these permissive and provocative factors increase the likelihood of FAS/ARBDs because they potentiate two related mechanisms of alcohol-induced teratogenesis, specifically, maternal/fetal hypoxia and free radical formation.