Effect of testosterone on medial preoptic/anterior hypothalamic neurone responses to stimulation of the lateral septum.
Electrophysiological recordings were made from medial preoptic/anterior hypothalamic (MPOAH) neurones which could be orthodromically excited from the lateral septum (LS) in gonadally intact and castrated male rats. Castration significantly reduced the mean percentage of MPOAH neurones which responded reliably to 0.6 Hz stimulation (from 81.1% to 54.1%) and this could be reversed by testosterone propionate (from 52.5% to 90.1%). Both in the gonadally intact (58.1%) and castrated (53.8%) groups these MPOAH neurones with LS inputs also had inputs from the contralateral fimbria (CFIMB). A further experiment investigated whether these MPOAH neurones responding to LS stimulation had connections with the arcuate/median eminence (ARC/ME) region or the medial forebrain bundle (MFB). Altogether, 23.2% projected directly into the MFB and 9.5% into the ARC/ME. A further 28.4% and 31.6% of these MPOAH neurones received inputs from these respective brain regions. A small population of MPOAH neurones were also found which could be driven antidromically both from the LS and the MFB. Results show that testosterone alters the responsiveness of MPOAH neurones to stimulation of the LS. Since subpopulations of these neurones project to the MFB and ARC/ME the effects of castration on them may reflect both changes in sexual behavior and, for example, gonadotropin release.
D000818:Animals; D007025:Anterior Hypothalamic Nucleus / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D002369:Castration; D004558:Electric Stimulation; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009928:Organ Specificity; D011301:Preoptic Area / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013739:Testosterone / Q000494:pharmacology*
D013739:Testosterone