Neuroendocrine correlates of testosterone-induced changes in brain evoked responses to afferent input.

Evoked responses (ER) to stimulation of spermatic nerve were picked up in conscious monkeys from hypothalamic limbic and cerebral cortical regions. The effect of intravenous injection of testosterone propionate (TPss; 0.4 mg/kg) on ER was examined in the same animal. Hormone administration caused inhibition or potentiation of ER in different regions of brain. The duration of hormone effect also suggested area specificity. A significant, immediate reduction in ER amplitude was produced by hormone injection in the ventromedial nucleus. On the contrary an increase of ER was observed in the anterior hypothalamus and in several limbic areas. Genital sensory motor cortex showed slight potentiation. The results support the hypothesis proposed in earlier EEG studies that TP and genital afferent input probably play a selective role in brain mechanisms underlying organized and integrated expression of reproductive functions.