Short term variation in serum luteinizing hormone and testosterone in the male Japanese quail.

A series of experiments was conducted to examine the incidence of short-term variation in serum testosterone and luteinizing hormone (LH) in the male Japanese quail. Individual samples were taken at 15-min intervals for blocks of time during the day or night. Serum testosterone concentrations did not vary significantly between 1100 and 1600 hr. Comparison of fluctuations in serum testosterone between 1300 to 1430 hr and 0100 to 0230 hr again revealed no significant change during the day, and a highly significant peak during the nocturnal sample. In two experiments, significant variations were observed in serum testosterone and LH between 10 and 14 hr after the onset of light. Pulses in LH preceded those of testosterone by up to 75 min. These experiments substantiate previous reports of episodic fluctuations of LH in avian species and provide evidence of episodes in peripheral levels of serum testosterone in the male Japanese quail.