Schedule-induced chronic hypertension.

Rats were fed on an intermittent-feeding schedule one 45-mg food pellet every 90 sec for 5 hours per day (experimental group) or an equivalent food ration as a single, daily feeding (control group). All animals were mononephrectomized and given saline to drink. Experimental animals became polydipsic (schedule-induced polydipsia). The rate and amount of fluid intakes between the two groups were controlled in the second experiment. In both experiments a significant blood pressure difference developed between the groups and remained terminally after water replaced saline as the drinking fluid for about 3 weeks. The development of chronic hypertension in the experimental group in the second experiment is regarded as a psychosomatic counterpart of other excessive and persistent behaviors (e.g., polydipsia, aggression), which can be induced by certain intermittent-feeding schedules. Observations on the heart (increased weight), kidney (minor pathologic changes), and adrenals (no change) were consistent with essential hypertension.