BRAIN-STEM MICROSTIMULATION DIFFERENTIALLY INHIBITS PUDENDAL MOTONEURON REFLEX INPUTS

SENSORY information from the genitourinary tract is transmitted to per ineal muscle reflex circuits in the spinal cord and to the medullary r eticular formation (MRF). This is the first report of a functional des cending connection between neurons in the MRF and sensory inputs of th e pudendal motoneuron reflex circuitry. In anesthetized rats, microsti mulation of the MRF produced a decrease in amplitude and increase in l atency of pudendal motoneuron reflex discharges (PMRD) elicited by sti mulation of the dorsal nerve of the penis. No effects on pelvic nerve- elicited PMRD were found. The most robust reflex depression was observ ed when the lateral paragigantocellular reticular nucleus was microsti mulated bilaterally. Reproductive abnormalities that occur following s evere spinal cord injury probably result from disruption of these desc ending connections.