Diurnal changes in the plasma concentrations of LH and hypothalamic contents of LHRH-I and LHRH-II in the domestic hen

Diurnal changes of LH secretion in sexually immature hens of 9, 11, 13 and 15 weeks of age consisted of 25-40% increases in the mean concentrations of LH in plasma between 15.00 and 18.00 h, i.e. between 2 h before and 1 h after the onset of darkness. During this time there was a tendency for the mean contents of LHRH-I in the anterior hypothalamus and postarior hypothalamus to increase by 21-74% and 20-56% respectively