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 implanted into the lateral septum in male rats increases LH and FSH secretion. However, it was unclear whether the effect of testosterone was direct via androgen receptor, or indirect via the estrogen receptor after conversion by aromatization to estradiol. To answer this question, we implanted either testosterone 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 testosterone 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 figure that increased to 0.7 +/- 0.12 and 0.55 +/- 0.1 ng/ml after DHT or testosterone implantation respectively. Mean concentration of FSH in control animals 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 +/- 5 ng/100ml) nor plasma testosterone levels (4.1 +/- 0.38 vs. 3.3 +/- 0.18 ng/ml) were significantly affected by the implants. We conclude that androgens independently of conversion to estrogen acting in the lateral septum facilitates the release of LH and FSH.