Circadian Adrenal Cycle in C Mice kept without Food and Water for a Day and a Half

Abstract

CERTAIN rodents (as also is the case with man) show circadian (about 24-h; circa, dies^1–3) rhythms in many body functions. Prominent among these rhythms is the adrenal cycle, gauged indirectly by observations on functions influenced by corticosteroids^4,5 and directly by determinations of corticosterone in serum^6–9 and in the adrenal gland itself¹⁰. Investigations of an indirect index, the blood eosinophil rhythm, suggested that the adrenal cycle persists in mice kept under conditions which gravely alter the œstrus cycle, such as the prolonged 50 per cent reduction in dietary calories¹¹. This communication summarizes shorter-term work with a more direct index, that is, the level of corticosterone in serum and adrenals. Circadian periodic changes in these indices as well as in rectal temperature and pinnal mitoses continue in C mice deprived of all food and water for 36 h.