Micturition evoked by glutamate microinjection in the ventrolateral periaqueductal gray is mediated through Barrington's nucleus in the rat

Neural tracing experiments have demonstrated a direct spinal projection to Barrington's nucleus and a possible indirect pathway to Banington's nucleus via the periaqueductal gray. We sought to identify the role of the periaqu eductal gray matter in micturition in urethane-anesthetized rats. Blockade of micturition by focal injection of cobalt chloride was used to identify s ites critical to micturition. These sites were located near the ventral mar gin of the caudal ventrolateral periaqueductal gray and in Barrington's nuc leus. L-Glutamate injections into caudal regions of the periaqueductal gray evoked bladder contraction with coordinated sphincter activation. Addition al L-glutamate sites with a similar pattern of response and sites where sph incter activation was produced without bladder contraction were found more rostrally and dorsally in the periaqueductal gray. Activation of bladder co ntractions by L-glutamate injection in the ventrolateral periaqueductal gra y was blocked by prior injection of cobalt chloride into Banington's nucleu s. From these data we propose that ventrolateral periaqueductal gray is functi onally important to micturition in the urethane-anesthetized rat. Further, we have shown that a periaqueductal gray to Banington's nucleus pathway is functionally relevant to central mediation of bladder contraction. (C) 2000 IBRO. Published by Elsevier Science Ltd. All rights reserved.