Crystalline dihydrotestosterone implants in the lateral septum of male rats. A positive effect on LH and FSH

Previous investigations in our laboratory have shown that testosterone impl anted into the lateral septum in male rats increases LH and FSH secretion. However, it was unclear whether the effect of testosterone was direct via a ndrogen receptor, or indirect via the estrogen receptor after conversion by aromatization to estradiol. To answer this question, we implanted either t estosterone or the non-aromatizable androgen 5 alpha -dihydrotestosterone ( DHT), into the lateral septum of adult male rats and measured plasma levels of LH and FSH by radioimmunoassay 2 days after implantation. Both testoste rone and DHT significantly increased the plasma LH and FSH concentrations. Mean concentration of LH in control animals was 0.21 +/- 0.06 ng/ml, a figu re that increased to 0.7 +/- 0.12 and 0.55 +/- 0.1 ng/ml after DHT or testo sterone implantation respectively. Mean concentration of FSH in control ani mals was 1.5 +/- 0.3 ng/ml; this figure increased to 3 +/- 0.3 and 2.9 +/- 0.3 ng/ml after DHT or testosterone implantation. Neither plasma DHT (64.0 +/- 5.6 vs. 52 +/- 5ng/100ml) nor plasma testosterone levels (4.1 +/- 0.38 vs. 3.3 +/- 0.18 ng/ml) were significantly affected by the implants. We con clude that androgens independently of conversion to estrogen acting in the lateral septum facilitates the release of LH and FSH.