Effect of electrical stimulation of the baso-lateral amygdala nucleus on defensive burying shock probe test and elevated plus maze in rats.

In the present report, the putative effect of a single electrical stimulation (75, 150 or 300 microA) to the baso-lateral amygdala (BLA) nucleus was assessed in shock probe defensive burying behavior test (DB) and elevated plus maze (EPM). These models have been used for measuring anxiety levels and screening putative anxiolytic compounds. A group of 28 rats were randomly divided for the following experimental conditions: Control-control, sham-operated, BLA stimulated groups: 75, 150 and 300 microA tested for DB. The cumulative defensive burying in a 15 min-test, the latency of burying, the number of shock received and the height of the bedding material in the probe were recorded. Another group of 28 individuals was also randomly distributed for the following experimental conditions: Control-control, sham-operated, BLA stimulated animals: 75, 150, 300 microA and tested in the EPM. The time the subjects spent in the open arms, the crosses and the faeces number excreted during the test were recorded. Decreased levels of defensive burying were observed in 75, 150 and 300 microA stimulated groups. The 150 and 300 microA groups reached statistical significance. The fact that 300 microA stimulated group showed statistically significant increase in the latency of defensive burying, in the number of shock received and decreased amount in bedding material suggests a sedative action of electrical stimulation. Increased time in the open arms and augmented number of crossings in 150 microA group was observed. No changes in the number of faeces were observed in any group. The evidence supported the notion of an inhibitory amygdaline mechanism triggered by sub-threshold electrical stimulation.

The effects of chronic chlordiazepoxide administration on ingestion of edible and nonedible substances by rats.

Chronic administration of chlordiazepoxide (CDP) is known to increase feeding in several species and under different procedures. Although this effect does not appear to result from antineophobic and anxiolytic effects of this benzodiazepine, very little is known about the possible contribution of stereotyped nibbling and chewing responses to enhanced feeding. The present study addressed this issue. Experiments 1 and 2 showed that rats injected with 5 and 10 mg/kg CDP spent more time chewing wood than either food-deprived or satiated rats. Experiment 3 showed that rats chronically injected with CDP spent more time chewing biscuits than wood in choice tests; with repeated choice testing chewing biscuits increased while chewing wood decreased. Experiment 4 replicated these results, and ruled out the possibility that increased time chewing resulted only from the self-rewarding effects of chewing. Finally, Experiments 3 and 4 also showed that despite these strong local effects on feeding time, body weight and the amount of food and water ingested every day for 10 days were not increased by 5 and 10 mg/kg CDP. It is unlikely that the effects of CDP on feeding results only from induction of stereotyped nibbling and chewing.

Effects of chlordiazepoxide on food anticipation, drinking and other behaviors in food-deprived and satiated rats.

Two groups of rats, Deprived and Satiated, were presented with food according to a fixed time 60-sec schedule. They were then injected with saline, 5, 10, and 15 mg/kg of chlordiazepoxide hydrochloride according to a Latin square design. During saline administration time spent visiting the food tray, time spent drinking, number of tray entries and the amount of water ingested were always greater in the Deprived than in the Satiated group; whereas the opposite was true for grooming. As chlordiazepoxide dose increased time spent visiting the food tray increased in both groups, but the effect was bigger in the Satiated than in the Deprived group. Drinking was not affected by the drug. Grooming and sniffing-rearing were reduced as the dose increased.

Food and water intake in the non-deprived pigeon after chlordiazepoxide administration.

Food and water intake were measured in non-deprived pigeons over a 4h period during daytime. Under control conditions, the ratio of food to water intake was approximately 1:1, and both intakes were a simple linear function of time. Chlordiazepoxide (10 mg/kg, i.m.) doubled the mean amount of food intake, whilst leaving water intake unchanged. This is a first indication that chlordiazepoxide can selectively stimulate appetite for food in an avian species. Some birds showed sedation following a first acute injection; its duration was shortened after repeated injections, and the hyperphagic response to the drug was revealed.

The effects of various protein synthesis inhibitors on the sleep-wake cycle of rats.

The present investigation sought to determine the effects of Anisomycin (A), Chloramphenicol (ChA), Vincristine (V), and Penicilline G on the sleep-wake cycle of rats. It was found that both high and low doses of anisomycin decreased rapid eye movement (REM) sleep, while only high doses of ChA and V produced such a decrease. Slow wave sleep (SWS) was unaffected by these drugs. Penicilline G, on the other hand, had no effect on the sleep-wake cycle. It was further shown that the reduction of REM sleep was the result of a decrease in the number of REM periods rather than in the duration of each individual period. These results suggest that protein synthesis may participate in the mechanisms that trigger REM sleep.