Dopamine antagonists do not block testosterone-induced decrease in luteinizing hormone.

These studies were designed to test the hypothesis that testosterone might lower circulating levels of luteinizing hormone (LH) in castrated male rats by activating dopaminergic neuronal systems. Blood samples were drawn from conscious rats through an indwelling cannula during the fourth and eight hours after subcutaneous administration of testosterone (1 or 5 mg/kg, in corn oil). Testosterone caused a dose-dependent decrease in plasma LH levels eight hours after administration. This decrease was not blocked by prior administration of the dopaminergic antagonists haloperidol and flupenthixol. This lack of effect of dopaminergic antagonists indicates that testosterone does not act primarily via dopaminergic activation to lower LH.