Specificity of androgenic regulation of input to sexually dimorphic motoneurons in male rat lumbar spinal cord.

Averaged antidromic field potentials were recorded near motoneuronal somata of the spinal nucleus of the bulbocavernosus (SNB) after stimulation of their axons, in intact, castrated, and testosterone-treated castrated male rats under urethane anesthesia. When the SNB motoneurons were antidromically activated with double pulses to the bulbocavernosus (BC) nerve, the first pulse inhibited the antidromic response caused by the second pulse at interstimulus intervals of 5-40 ms, implying the presence of recurrent or other inhibition activated by BC nerve stimulation. Castration and androgen treatment had no significant effect on the amplitude of the suppression. In this regard this pathway differs from other pathways that synapse onto SNB motoneurons, in which activity is highly sensitive to androgen, indicating that androgen exerts its effects only on specific neural circuits that influence SNB motoneurons.