Effects of arginine vasopressin and angiotensin II on area postrema neurons in rabbit brain slice preparation.

Previous in vivo studies have indicated that both arginine vasopressin (AVP) and angiotensin II (ANG II) can modulate the baroreflex by acting on the area postrema (AP). In the present study, effects of AVP and ANG II on AP neuronal activity were investigated by recording extracellular activity in a rabbit brainstem slice preparation. AVP (1 nM-1 microM) inhibited 14.5% and excited 53.2% of the neurons while ANG II (1 nM-5 microM) inhibited 32.3% and excited 29% of the neurons. Application of AVP and ANG II to the same AP neurons at the same concentration indicated that more AP neurons responded to AVP than to ANG II. ANG II induced more inhibitory responses than AVP. The results suggest that AVP and ANG II may produce different effects on the baroreflex by acting on different pools of AP neurons and by exerting different effects on the same AP neuron.