Hypothalamic neurons responsive to increased plasma level of testosterone in the male rat

Unitary activity was recorded from several forebrain structures. Out of 108 cells, 35 reacted to a testosterone i.v. injection by an increase (24 cells) or a decrease (11 cells) of firing rate. This response was early (latency: 5.0 +/- 0.6 min), lasted 25.7 +/- 1.9 min and was reproducible. Responsive neurons were found to be significantly more numerous in the lateral hypothalamic area than in other structures.