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.
- Gonadal regression
- Luteinizing-hormone-releasing hormone
- Luteinizing-hormone-releasing-hormone-associated peptide
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Endocrine and Autonomic Systems
- Cellular and Molecular Neuroscience