THE CAUDAL VENTROLATERAL MEDULLA IS A SOURCE OF TONIC SYMPATHOINHIBITION

The caudal ventrolateral medulla (CVLM) contains neurons that are esse ntial for the elaboration of the sympathoinhibitory effects of barorec eptor afferent stimulation. To determine if neurons in the CVLM also m ediate a tonic inhibition of sympathetic nerve activity (SNA), we exam ined the effects of lesioning CVLM neurons in baroreceptor-denervated rats. The sustained increases in both arterial pressure (AP; 40 mmHg) and splanchnic SNA (200%) indicate that the discharge of neurons in th e CVLM maintains a tonic sympathoinhibition that contributes significa ntly to the maintenance of normotensive levels of SNA and AP.