Endocrinology, Vol 121, 200-204, Copyright © 1987 by Endocrine Society

ARTICLES

In vitro evidence for short-loop gonadotropin feedback on gonadotropin- releasing hormone neurons harvested from adult male rats

PA Melrose

GnRH neurons were harvested from adult male rats in order to determine if LH or FSH directly altered the modalities of GnRH release and/or cellular GnRH content. Cultures received vehicle, 25 ng/ml LH, 125 ng/ml LH, 25 ng/ml FSH, or 125 ng/ml FSH, and media samples were collected before treatment, during the treatment pulse, and at 24 h post treatment; cellular GnRH content was determined 48 h post treatment. Both LH treatments used in this study acutely increased the frequency of spontaneous GnRH pulses and the mean media GnRH concentration. Further, neurons treated with an LH pulse exhibited large amplitude GnRH pulses during the treatment period. In contrast, FSH treatments had no effect on mean media GnRH concentrations and the 25 ng/ml FSH treatment did not alter neurosecretory modalities of spontaneous GnRH release. The neurons which received 125 ng/ml FSH did however exhibit large amplitude GnRH pulses during the gonadotropin pulse. This latter treatment was also associated with reduced cellular GnRH content whereas neuronal GnRH content was not affected by the 25 ng/ml FSH treatment or by LH treatments. These results suggest that both LH and FSH may interact directly with GnRH neurons to elicit a change in the modalities of GnRH release and that FSH may also act to reduce cellular GnRH content.

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