Caudal ventrolateral medulla can alter vasopressin and arterial pressure

The effects of specific treatments of the caudal ventrolateral medulla (CVLM) on vasopressin (AVP) release and arterial pressure (AP) were examined in urethane-anesthetized rabbits. Electrical stimulation of the CVLM for 5 minutes did not increase plasma AVP; it did however elicit an acute fall in arterial pressure. Similarly, stimulation of cells in the CVLM by microinjection of L-glutamate caused an acute decrease in AP but no change in plasma AVP. Muscimol injected into the CVLM increased AP but not AVP. On the other hand, bicuculline decreased AP and markedly increased plasma AVP, and the increase in AVP following bicuculline injection was not secondary to the fall in AP. These results demonstrate that the CVLM is involved in the regulation of AVP release. Furthermore, taken together with previous findings, these studies indicate that AVP and AP respond differently to treatments of the CVLM, suggesting that different cells in the CVLM are involved in the regulation of AVP release and AP.