Effect of constant light and darkness on the circadian rhythms in rats: I. Food and water intake, urine output and electrolyte excretion.
The light/dark (L/D) rhythms of food and water intake, urine output and Na+, Cl- and K+ excretion were studied in male Wistar albino rats subjected either to constant light (LL) or darkness (DD). The LL regimen had a suppressive effect on the daily food and water intake, urine output and sodium excretion, combined with an elimination of L/D variations in all parameters studied. The DD regimen caused a decrease of the daily food and water intake, and sodium and chloride excretion. The L/D rhythms of water and electrolyte excretion were eliminated, while the diurnal rhythms of food and water intake were attenuated but still persisted after 16 days of DD. Our results suggest that the L/D cycle is the major external synchronizer of the circadian rhythms of water and electrolyte excretion in the rat. In the absence of L/D cyclicity, the persisting periodicity of food intake is not a potent enough synchronizer of the circadian rhythms of water and electrolyte excretion. Probably, the circadian rhythms of food and water intake from one hand, and the rhythms of renal excretion from the other hand, are regulated via different circadian mechanisms in the rat.
D000818:Animals; D002712:Chlorides / Q000652:urine; D002940:Circadian Rhythm; D003624:Darkness; D004326:Drinking; D004435:Eating; D008027:Light; D008297:Male; D011188:Potassium / Q000652:urine; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000652:urine; D014554:Urination
D002712:Chlorides; D012964:Sodium; D011188:Potassium