Effects of Timed Melatonin Infusion on Prolactin Secretion in Pineal Denervated Goat
作者:
Yuji Mori,
Hiroaki Okamura,
期刊:
Journal of Pineal Research
(WILEY Available online 1986)
卷期:
Volume 3,
issue 1
页码: 77-86
ISSN:0742-3098
年代: 1986
DOI:10.1111/j.1600-079X.1986.tb00728.x
出版商: Blackwell Publishing Ltd
关键词: melatonin;prolactin;pineal gland;goat;ganglionectomy;photoperiod
数据来源: WILEY
摘要:
The effects of timed melatonin infusion on prolactin secretion were examined in the pineal denervated goat. Ovariectomized Shiba goats (n = 5) were subjected to bilateral superior cervical ganglionectomy (SCGX); this procedure resulted in complete abolition of endogenous melatonin release during the dark phase. SCGX goats failed to coordinate their prolactin secretion with the prevailing photoperiod. Melatonin was infused (20 μg/h, s. c.) daily into these goats either for 8 h (the long‐day‐type infusion) or for 16 h (the short‐day‐type infusion) to mimic the nocturnal profile of plasma melatonin under long days or short days, respectively. The long‐day‐type melatonin infusion for 9 days, in comparison with control saline infusion, accelerated prolactin secretion, inducing a nocturnal rise in plasma prolactin; this was comparable to that seen in the pineal intact goats under long photoperiods. On the other hand, the short‐day‐type melatonin infusion suppressed prolactin secretion throughout the day as the short‐day treatment did in intact goats. The prevailing photoperiod appeared to have no distinct effect on these prolactin responses to exogenous melatonin, which were indistinguishable under 16L8D and 8L16D conditions. The results indicate that the information about external light‐dark cycles is converted by the pineal gland into the endocrine signal as a daily pattern of melatonin secretion, which eventually regulates prolactin secretion from the pituita
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