The involvement of amygdala nucleus in chronic stress induced changes on ingestive behavior of wistar rats.

Organisms are constantly subjected to stimuli that can be construed as stressors. Stress regulation is a highly integrated process controlled largely by the brain. The role of amygdala in stress tolerance has attracted continued interest because of its central role in processing emotional information. In the present study, the Wistar albino rats were subjected to chronic swimming (physical) stress and chronic immobilization (psychological) stress for 60 days with or without bilateral lesions of the nucleus of amygdala. Their food intake, water intake and body weight were measured. Exposure to stressors significantly decreased the body weight, food and water intake whereas amygdala lesioning significantly increased the body weight (P<0.001), food intake (P<0.001) and water intake (P<0.001).However, the stress induced decrease observed in the body weight and food intake of the amygdala lesioned groups was significantly more (P<0.001) during immobilization stress than swimming stress. It can be concluded that amygdala nucleus appears to play a prominent role in minimizing the stress induced changes in the food intake and body weight; and this role was more evident in immobilization stress than a physical stress. Thus, the present study support the notion that the amygdala nucleus play a definite role in minimizing stress induced changes in the ingestive behavior and its role in psychological stress is more prominent.

Effect of acute and chronic conditions of over-crowding on free choice ethanol intake in rats.

Male albino rats of Wistar strain were exposed to overcrowding stress in two different groups for a period of seven days. One group of rats was kept under stress for six hours per day (acute stressed group) and the other group rats was kept under stress continuously (chronic stressed group). The effect of these acute and chronic stresses on voluntary alcohol (2% w/v) intake was monitored during the 7 days of stress exposure, and ethanol preference and total ethanol intake in terms of g/kg body weight were also studied. A significant increase in ethanol preference and ethanol intake was observed in one-day and 7 days chronic stressed group. No significant increase in ethanol intake was observed in acute stress. Thus a short lasting stressor may not increase ethanol-drinking behavior, whereas when animals were exposed to more intense stressor continuously for 7 days, an increase in voluntary drinking behavior may be seen.

Forced swimming stress induced alterations in ingestive behavior in rats.

The effects of forced swimming stress (15 minutes per day) on body weight, food intake, blood sugar, water intake, and urine output were studied in adult male Wistar rats on the first, seventh, fourteenth and 21st days in different subgroups. There was a significant initial decrease in the body weight up to 14 days followed by a regain in the body weight, which was sustained until 21 days. Though there was no change in the food intake initially for 7 days, after 14 days a significant increase in the food intake was observed. A significant hypoglycemia was observed throughout the entire period of stress. More significant fall in the blood sugar level was observed in the initial period of exposure of stress (1-7 days). There was a significant reduction in the water intake in the stressed animals. Urine output decreased significantly up to 7 days of stress, though it got marginally increased later. Thus, repeated stress may produce a reduction in body weight only initially, which is accompanied with an initial decrease in food and water intake also. The peak response to stress was seen after 7 days of stress exposure. There was a gradual recovery back to normal in the body weight, food intake, and water intake and urine output when stress period was prolonged to 14-21 days. This is suggestive of the adaptation of the organism to repeated exposure of similar kind of stress.

Voluntary alcohol drinking & caloric intake in rats exposed to crowding stress.

BACKGROUND & OBJECTIVES: Alcohol intake in animals is regulated in much the same way as intake of food. The effect of alcohol on feeding behaviour is not well documented. The objective of this study was to test whether alcohol was ingested as a source of calories after crowding stress in rats. METHODS: Male albino rats were exposed to crowding stress continuously for two weeks and the effect of stress on the body weight, food intake, voluntary alcohol consumption and caloric intake in terms of food and alcohol was studied. RESULTS: A significant decrease in the body weight was seen after one (P < 0.05), 7 and 14 days (P < 0.01) of stress compared to controls. Food intake decreased significantly (P < 0.01) after one day of stress and there was recovery after 7 days stress. Absolute alcohol intake (g/kg body weight) increased significantly (P < 0.001) after one day of stress. Prolonged stress for two weeks significantly (P < 0.01) increased the alcohol consumption. Total caloric intake in stressed rats decreased significantly (P < 0.001) after acute stress. After 14 days, stressed rats showed significant (P < 0.001) increase in total caloric intake compared to day one. INTERPRETATION & CONCLUSION: Crowding stress decreased the body weight gain throughout the period of stress. Chronic stress for two weeks increased the voluntary alcohol consumption and total caloric intake. Food intake alone seemed insufficient to provide the extra demand of energy due to prolonged stress and hence, the rats may be drinking increasing amounts of alcohol (when provided) to supply the extra energy required to combat stress.

Influence of different types of stress on selected cardiovascular parameters in rats.

Wistar strain male albino rats were exposed to different types of stressors like isolation, immobilization, overcrowding and forced swimming, for a duration of one day, 7 days, 15 days and 30 days and the effect on heart weight, adrenal weight, heart rate, P-R interval and serum transaminase levels were studied. There was a significant increase in the heart weight and adrenal weight in most of the stress subgroups. Tachycardia was seen in all the types of stress upto 7 days, except in the case of overcrowding stress. Serum transaminase level increased significantly in all the types of stress. Among the different types of stress, immobilization and forced swimming had greater effect on the heart weight and heart rate. Increase in the heart rate and heart weight was observed only in the initial period of exposure to a stressor and when the animals were exposed to a prolonged stressor like 15 days and 30 days, there was no further increase in the heart weight and heart rate which may be due to the adaptation of the animal to a chronic stressor.