Steroid Effects on the Secretory Modalities of Gonadotropin-Releasing Hormone Release*

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Abstract
GnRH neurons isolated immunochemically from the brain of adult male rats were used to determine whether testosterone (T), dihydrotesterone (DHT), estradiol-17.beta. (E17.beta.), 20H-estrone (OHE1), or progesterone (P4) have a direct effect on the spontaneous neurosecretion and/or cellular content of GnRH. Neurons harvested from interval rats were treated with a single steroid pulse; samples were collected before treatment, during the steroid pulse; samples were collected before treatment, during the steroid pulse and at 24 h post treatment. Androgen treatments of 100 pg/ml or 1 ng/l media elicited an increase an GnRH pulse frequency 1-6 min after steroid exposure without affecting the amplitude of release; these modalities persisted at 2 h. The frequency of GnRH pulse was increased 24 h after the neurons received the brief 100 pg/ml or 1 ng/l T or 1 ng/ml DHT treatments. Neurons exposed to androgen treatment also appeared to express a large amplitude TnRH uses infrequently at the time whereas there was no androgen affect on the cellular GnRH concentration. In contrast, E217.beta., OHE1, and P4 treatment had no effect on the mean media GnRh concentration, baseline EGnRH concentration, or on the frequency and amplitude of GnRH uses at any time point. However, the 1 ng/ml P4 and the 1 ng/l OHE1 treatments both reduced cellular GnRH content at 48 h post treatment. These results suggest that T and DHT may specifically interact with TnRH infusion to elicit immediate and/or long-term changes in the modalities of neuropeptide release and that under physiological conditions GnRH neurons of adult male rats are not directly influenced by E217.beta., the catecholestrogen OHE1, or P4.