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Modulation of gonadotropin‐releasing hormone neuronal activity as evidenced by uptake of fluorogold from the vasculature
Author(s) -
Silverman AnnJudith,
Witkin Joan W.,
Silverman Rachel C.,
Gibson Marie J.
Publication year - 1990
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/syn.890060206
Subject(s) - medicine , endocrinology , castration , immunocytochemistry , luteinizing hormone , gonadotropin releasing hormone , estrogen , hormone , ovariectomized rat , hypothalamus , gonadotropin , chemistry , biology
Peripheral injections of the tracer fluorogold (EG) and immunocytochemistry were used to study the modulation gonadotropin‐releasing hormone (GnRH) cell secretory activity in adult mice. Intraperitoneal adminstration of FG would make it available to all GnRH terminals outside the blood‐brain barrier. The degree of capture of the dye would be linked to exocytotic (e.g., secretory) events at the nerve terminal. Single injections of tracer were made into intact mice of both sexes, and this resulted in the retrograde labeling of two‐thirds of the GnRH cell bodies. Administration of identical doses to 3 week castrate mice revealed a reduction in the percentage of GnRH cells, with detectable FG, to 40% of the total. Castration did not diminish the number of GnRH cells visualized. When castrate animals received two doses of FG, the number of GnRH cells with tracer was increased to slightly greater than intact levels. This suggests that the secretory rate of individual GnRH cells might be reduced under coditions of castration. In addition, when ovariectomized females treated with estrogen and progeserone to induce luteinizing hormone (LH) surge were injected with FG just prior to that surge, over 80% of the GnRH neurons were robustly labeled with FG. These latter data are interpreted as representing GnRH neurons at maximally synchronized activity. This study suggests that peripheral administration of FG can be used in this species to follow alterations in neurosecretory rates.