Different electrophysiological effects of testosterone on medial preoptic/anterior hypothalamic neurons have similar time courses.

The time courses of different electrophysiological effects of testosterone on a specific subpopulation of medial preoptic/anterior hypothalamic neurons and sexual behavior were measured in castrated rats. Testosterone reduced the absolute refractory period of those neurons projecting into the medial forebrain bundle with the same time course as it restored maximal responsiveness to orthodromic stimulation of either the lateral septum or the fimbria and sexual responses (5 days). The similar time-courses for these different electrophysiological effects of testosterone argue for a common mechanism of action.