Bimodal distributions of highest ethanol acceptance concentrations in two strains of rats.

Two groups of non-deprived male Wistar rats and one group of male Sprague-Dawley rats were offered a choice of water and daily-increasing concentrations of ethanol. Each group's distribution of highest ethanol acceptance concentrations approximated a bimodal distribution with respect to concentration. Further, rats in each group which drank ethanol at high concentrations maintained relatively constant intakes of pure ethanol. These results are discussed in terms of taste and olfaction, central nervous system sensitivity and emotionality.

Discriminative stimulus properties of clozapine and chlorpromazine.

Rats were trained to discriminate pairs of drug states in a two-lever operant paradigm for food reinforcement. One group learned to discriminate clozapine from vehicle, a second group learned to discriminate chlorpromazine from vehicle, and a third group learned to discriminate clozapine from chlorpromazine. The result that the clozapine versus chlorpromazine discrimination was acquired, as well as the results of substitution tests with non-training drugs, suggest that the stimulus properties of the classical neuroleptics and other psychotherapeutic agents indicate that the stimulus properties of antipsychotics are distinct from other classes of psychotropic agents, and support the hypothesis that clozapine may be a unique antipsychotic. It is suggested that the unique discrimination stimulus produced by clozapine may be related to the differential effect of the drug on the extrapyramidal versus accumbens dopamine system.

Endocrine factors contributing to the ethanol preferences of rodents.

Groups of C57 Bl/6j mice (alcohol preferring) and DBA/2j mice (alcohol avoiding) were fasted for 24 hours and administered glucose. At 30, 120 and 300 minutes after glucose, the C57 Bl/6j mice had significantly higher levels of plasma glucose than the DBA/2j strain. These differences were observed in comparable groups given either forced access or no access to alcohol. In ad lib fed animals never exposed to alcohol, C57 Bl/6j mice had higher levels of plasma insulin than DBA/2j mice. Plasma levels of glucose and corticosterone were not significantly different in ad lib or fasted animals. The injection of insulin zinc protamine to DBA/2j mice produced 100% convulsions within one hour, but produced to convulsions in C57 Bl/6j mice for as long as 4 hours after administration. These data demonstrate that an insulin resistancy exists in C57 Bl/6j mice which is not dependent upon any prior alcohol experience. Evidence supporting a functional relationship between this diabetogenic disturbance and alcohol preference was obtained in C57 Bl/6j mice which were allowed to choose between water or a 10% alcohol solution (v/v). Insulin zinc protamine produced a selective dose-dependent reduction in alcohol intake. Additional support is received from the discovery that Chinese hamsters, a species genetically predisposed to diabetes, display an impressive preference for 10% alcohol.

Age-related differences in behavior across the life span of the C57BL/6J mouse.

C57Bl/6J mice, representing four divergent age groups (ranging from 3 months to 31 months) were each tested on a number of behavioral procedures, selected to sample a wide spectrum of behaviors. The evaluation demonstrated that, as with other mammalian species, not all behaviors in the mouse are affected by old age. Most severely impaired was retention of a single-trial passive avoidance task, most probably reflecting a deficit in memory ability. One tests of motor function, the most demanding tasks revealed the greatest debilitating effects of age, paralleling the effects of task difficulty previously reported in numerous learning studies. Finally, a deficit in the ability to modify preexisting habits in a T-maze learning situation was observed, corroborating reports of increased perseveration in aged humans and nonhuman primates. The similarity of these results across the life span of the C57 mouse with those previously reported for other aged mammalian species demonstrates that certain common types of behaviors seem to be impaired selectively by increased age across mammalian species and raises the possibility that common neurological etiologies may exist for these behavioral deficits.