Reflex activity of the pubococcygeus muscle is modified throughout the estrous cycle in Wistar rats.

Pubococcygeus muscle reflex activity has been reported to be driven by specialized neuronal circuitry, including the participation of spinal cord interneurons. Both the reflex and elements of the circuit are known to be sensitive to gonadal hormones, but studies using female rats have not considered the potential effects of estrous phase. Hence, in the present study we used mechanical stimulation of the clitoris to produce reflex activity, and recorded across the different phases of the estrous cycle, including the dark and light periods during each phase. Afterdischarge activity was observed only during the light and dark periods of proestrus, and during the light period of estrus coincident with the receptivity period in the rat́s reproductive behavior. Moreover, this reflex activity comprises at least five different motor unit groups with different firing patterns that are dependent on gonadal hormones variation.

Spinal cord neuronal components involved in the reflex activity of female rat pubococcygeus motoneurons.

Evoked EMG reflex activity from the pubococcygeus muscle of female Wistar rats has been reported, but has not been carefully analyzed. Here, we studied this reflex activity through mechanical stimulation of the clitoris, perigenital skin, caudal vagina and foot, all of which produced bilateral reflex multiunit electromyographic (MEMG) tonic "on" activity and displayed a rapid adaptation. However, deep vagina and cervical stimulation did not modify MEMG baseline activity even if it was combined with clitoris, perigenital skin and foot stimulation. Electrical stimulation of the dorsal nerve of the clitoris produced bilateral MEMG activity that when recorded at fast sweep speed, it was possible to observe that the ipsilateral response had an 8 ms latency, while the contralateral response had a 10 ms latency. These data suggest that bilateral reflex activation of pubococcygeus muscle motoneurons is produced by several sensory sources in which a specialized neural circuitry of afferent and efferent components and several spinal cord interneurons are involved. This is in accordance with the multi functionality of this muscle in reproductive and behavioral processes.