Circadian and Estrous Rhythms in Pineal Melatonin and 5-Hydroxy Indole-3-Acetic Acid.

Abstract

SummaryDifferential extractions and fluorometry of pineal 5-hydroxy indole-3-ace-tic acid and melatonin in adult rats demonstrate circadian rhythms correlated with periods of light and darkness and possibly influenced to a lesser degree by the estrous cycle. Pineal 5-hydroxy indole acetic acid in females rises from a nocturnal basal level of 4 ng/pineal to an early afternoon maximum of 18 ng/pineal and falls sharply at the start of darkness. Pineal melatonin rises at the start of darkness from 1 to 3 ng/ pineal; 5-methoxy indole acetic acid, averaging 0.98 ng/pineal, shows no circadian change. The specificity of the measurements and their implications for pineal indole metabolism and function are discussed.I am grateful to Mrs. Ann Richards, Mr. Brian Stross and Mr. Peter Baker for laboratory and animal room assistance.