Role of the pineal gland in photoperiod-induced changes in hypothalamic-pituitary sensitivity to testosterone feedback in castrated male hamsters

Fred W Turek*

*Corresponding author for this work

Research output: Contribution to journalArticle

30 Scopus citations

Abstract

An exposure to short days induces testicular atrophy in intact, but not pinealectomized, golden hamsters. Since recent evidence suggests that an alteration in the sensitivity of the hypothalamic-hypophyseal system to steroid feedback may be one way in which the photoperiod acts to alter neuroendocrine- gonadal activity in seasonally breeding animals, the present investigation was designed to determine if the pineal gland is involved in this photic-induced change to steroid feedback. Castrated adult male hamsters that had been sham-pinealectomized (Sham-Px) or pinealectomized (Px) were maintained on either stimulatory long days [14 h of light, 10 h of darkness (LD 14:10)] or nonstimulatory short days (LD 6:18) for 8 weeks. The animals were then implanted with various sized testosteronefilled capsules and serum was collected 10 and 21 days later for hormone analysis. Capsules which contained 2 or 4 mm powdered testosterone maintained serum testosterone levels between about 0.8-1.5 ng/ml, and induced at least a 10-fold reduction in serum levels of immunoreactive LH and FSH in Sham- Px animals maintained on LD 6:18. These size capsules had no significant effect on serum gonadotropin levels in Sham-Px animals maintained on LD 14:10. Higher doses of testosterone (8 and 20 mm long testosterone-filled capsules) suppressed serum gonadotropin levels in all Sham-Px animals. Pinealectomy did not significantly alter the inhibition of pituitary gonadotropin release by testosterone in animals on LD 14:10. In contrast, the increased responsiveness of the gonadotropin control center to steroid feedback observed in Sham-Px animals on LD 6:18 was prevented or suppressed by pinealectomy. These results indicate that the short day-induced increase in sensitivity of the hamster hypothalamic-hypophyseal axis to testosterone feedback is mediated, at least in part, by the pineal gland.

Original languageEnglish (US)
Pages (from-to)636-640
Number of pages5
JournalEndocrinology
Volume104
Issue number3
DOIs
StatePublished - Jan 1 1979

ASJC Scopus subject areas

  • Endocrinology

Fingerprint Dive into the research topics of 'Role of the pineal gland in photoperiod-induced changes in hypothalamic-pituitary sensitivity to testosterone feedback in castrated male hamsters'. Together they form a unique fingerprint.

  • Cite this