Seasonal and Photoperiod-lnduced Changes in Serum Prolactin and Pituitary Responsiveness to Thyrotropin-Releasing Hormone in the Mare

A. L. Johnson

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Experiments were conducted in the horse mare to study the effects of photoperiod and season on serum prolactin and pituitary responsiveness to thyrotropin-releasing hormone (TRH). Increasing the photoperiod to 16 hr light:8 hr dark beginning in December (Experiment 1) and September (Experiment 2) increased serum prolactin, but the rate of increase was greater when the photoperiod treatment was initiated in September. In addition, TRH-induced prolactin secretion was found to be affected by season, in that pituitary secretion (net increase in prolactin and total prolactin secreted) was significantly greater in June compared with that of January (Experiment 3). These data suggest that in the mare, photoperiod plays an important role in controlling circulating levels of prolactin, but that in addition to photoperiod, other seasonally related factors, such as temperature, are involved in modulating the seasonal rhythm of serum prolactin.

Original languageEnglish (US)
Pages (from-to)118-122
Number of pages5
JournalProceedings of the Society for Experimental Biology and Medicine
Volume184
Issue number1
DOIs
StatePublished - Jan 1987

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)

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