DIURNAL VARIATION AND THE EPISODIC RELEASE OF PLASMA GONADOTROPHINS IN JAPANESE QUAIL DURING A PHOTOPERIODICALLY INDUCED GONADAL CYCLE

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Abstract
SUMMARY: Blood samples were taken every 3 h, over a 27 h period, from (1) a group of 12 intact male quail on short days (lights on 09.00–17.00 h) and during the 2nd, 15th and 36th day of photostimulation (lights on 09.00–05.00 h); (2) 12 castrated male quail on the 2nd, 20th and 43rd long day, and (3) 12 intact male quail on the 12th long day. Plasma LH was measured in all samples and FSH in the 43rd long day castrate and 12th long day intact male samples. Although there was considerable variation in the levels of LH and FSH, both between birds and between samples taken from the same bird, statistical analyses failed to reveal any diurnal (or circadian) rhythm at any time. There was a marked correlation between the LH and FSH levels in all samples. Possible episodic LH secretion was investigated by taking blood samples every 15 min for between 3 and 6 h from six intact male quail and six laying females on long days. Samples were obtained from each bird at three time-periods which were arranged so as to overlap and cover the first 12 h of the daily photoperiod. Statistical analysis suggested that episodes of secretion occurred 6–10 times/day in males, and 4–8 times/day in females. The pulses appeared to occur at random.