Inhibition of renal sympathetic nerve activity by electrical stimulation of the hypothalamic paraventricular nucleus in anesthetized rats.

In an attempt to obtain direct evidence for involvement of sympathetic outflow in paraventricular nucleus (PVN)-induced depressor response, effects of electrical stimulation of the PVN on renal sympathetic nerve activity were examined in urethane-chloralose anesthetized rats. Low intensity stimulation of the PVN inhibited renal sympathetic nerve activity, whereas the high intensity stimulation evoked an excitation followed by long-lasting inhibition in renal sympathetic nerve activity. Latencies of the inhibitory and the excitatory responses were about 200 ms and 50-100 ms, respectively. The result suggests that a decrease in blood pressure induced by low intensity stimulation of the PVN is due to inhibiting the sympathetic outflow.