Circadian Rhythmicity of Hypothalamic CRH and its Central Nervous Regulation

Abstract

In contrast to the marked circadian rhythm of endocrine pituitary function only a slight fluctuation of hypothalamic CRH was observed in rats throughout the day. However, a standardized ether stress significantly reduced hypothalamic CRH in the morning and no alteration was observed in the evening, whereas pituitary ACTH increased for the same amount at each time of the day. The hypothesis is proposed that a special "rhythm center" in the CNS acts in an inhibitory way on hypothalamic hormone synthesis.

CRF - Pituitary ACTH - Ether Stress - Rhythm Center