Episodic release of LH in gonadectomized male Japanese quail

Blood samples were taken every 15 min (for 4.75 h) from six castrated quail on three separate occasions. The birds were first bled while under short days (comprising 8 h light : 16 h darkness per 24 h; 8L : 16D) and, subsequently, after 1 and 20 days under long days of 16L : 8D. The photoperiodic alteration produced a marked increase in the mean plasma LH concentration of each bird and in four instances the rise was evident after only 1 long day. Pulsatile release patterns were not detected in the plasma LH profiles obtained during exposure to short days or after 1 long day but were pronounced in all of the birds after 20 long days. The peaks (n = 19) occurred on average every 83 +/- 14 (S.E.M.) min and had an amplitude of 12.3 +/- 1.2 micrograms/l. After 35 days under 16L : 8D three of the quail were bled more frequently (every 8 min for 2.5 h), allowing the LH pulses to be measured more precisely. Each pulse was composed of a sudden increase in secretion followed by a slower decrease which lasted for approximately 30 min. The development and functional significance of episodic LH release in the quail is discussed.