Decrease in blood pressure by stimulation of the rat hypothalamic paraventricular nucleus with L-glutamate or weak current.

Effects of electrical and chemical stimulation of the paraventricular nucleus (PVN) of the hypothalamus on blood pressure were examined in rats anesthetized with urethane-chloralose. Focal electrical stimulation (10-25 microA, 50 Hz, 0.5 ms) of sites within the PVN consistently decreased blood pressure, while the stimulation of regions adjacent to the PVN produced no change or weak depressor response. Microinjection of L-glutamate (0.5 M, 80 nl) to the PVN consistently led to decreased blood pressure, while the same amount of saline injection had no effect. The depressor response was not affected by cervical vagotomy but was markedly reduced after intravenous administration of hexamethonium. The results suggest that activation of PVN neurons in rats leads to a decrease in blood pressure.