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

Abstract

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.

Keywords: Estrus cycle; Muscular multiunit activity; Pubococcygeus motoneurons; Reflex activity; Spinal reflex.