Feeding pattern and light-dark variations in water intake and renal excretion after suprachiasmatic nuclei lesions in rats.

Bilateral destruction of the suprachiasmatic nuclei (SCN) eliminated light-dark (L/D) variations in water intake and urine output in albino rats. The lesions abolished also the circadian rhythm of food intake, without changing significantly the 24 hour number of meals, total meal duration and 24 hour food intake. Only the L/D distribution of the number of meals was changed from 5.6/16.9 in control period to 12.7/12.9 after lesions. In contrast, the L/D distribution of sodium, potassium and chlorides excretions demonstrated attenuated but persistent nocturnal type. These data imply that SCN play a role of driving oscillator for the circadian rhythm of food intake, but probably are not the main synchronizer for the rhythms of electrolyte excretions.