Medial septal lesions: disruptions of microregulatory patterns and circadian rhythmicity in rats.

The microregulatory patterns of food and water intake were examined in male and female rats bearing medical septal lesions and in sham-operated controls. Medial septal ablation, although not affecting the total amount of food or water ingested, resulted in a profound disruption of the pattern of intake. Circadian rhythmicity was disrupted for a period, returning to normal by 25 days postlesion. Permanent disruptions occurred in feeding patterns in the rats with septal lesions ingested more frequent but smaller meals. There was also a marked increase in food-intake-associated drinking and a decrease in non-food-intake-associated drinking. The results are interpreted to reflect two separate independent effects, a general circadian disruption and an alteration in requlatory behavior produced by a chronic depletion of body fluid.