Immunocytochemical study of GnRH and GnRH-associated peptide in male syrian hamsters as a function of photoperiod and gonadal alterations

Elettra Ronchi, Chiye Aoki, Lewis C. Krey, Donald W. Pfaff

Research output: Contribution to journalArticle

Abstract

Hypothalamic luteinizing-hormone-releasing hormone (GnRH) and gonado-tropin-releasing-hormone-associated peptide (GAP) biosynthesis and storage were estimated by immunocytochemistry in male golden hamsters maintained in different photoperiods. Intact or castrated male hamsters with subcuta-neously inserted testosterone implants were exposed to long-day (14: 10) or short-day photoperiods (10: 14) for 4-8 weeks. Exposure to short photoperiod for 4 weeks, an interval characterized by a suppression of gonadotropin secretion but not gonadal regression, was associated with an increase in the number of GnRH- and GAP-immunoreactive cells in the diagonal band of Broca/medial septum. Furthermore, morphometric analysis revealed that these animals displayed significantly more GnRH but not GAP immunoreac-tivity in the median eminence as opposed to hamsters exposed to long-day photoperiods. In additional studies, gonadally regressed hamsters exposed to short day lengths for 8 weeks had equal numbers of GnRH cells as did the long-day controls. These patterns suggest that reproductive quiescence in golden hamsters is not the result of depletions of neuronal GnRH stores available for secretion.

Original languageEnglish (US)
Pages (from-to)134-145
Number of pages12
JournalNeuroendocrinology
Volume55
Issue number2
DOIs
StatePublished - Jan 1 1992

Keywords

  • Gonadal regression
  • Immunocytochemistry
  • Luteinizing-hormone-releasing hormone
  • Luteinizing-hormone-releasing-hormone-associated peptide
  • Photoperiod

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Endocrinology
  • Endocrine and Autonomic Systems
  • Cellular and Molecular Neuroscience

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