ABSTRACT
<p><b>OBJECTIVE</b>To investigate the role of nitric oxide in the inhibitory effect of somatic afferent input on the pressor response caused by electrical stimulation of the paraventricular nucleus of the hypothalamus (PVN).</p><p><b>METHODS</b>SD rats anesthetized by urethane were used in the study. Bipolar stainless stimulating electrode was inserted into PVN for electrical stimulation. Multi-barreled micropipettes were used for microinjection of L-NAME or normal saline into the lateral ventricle or amygdala. Deep peroneal nerve (DPN) was stimulated with electrical current pulses of 0.4 mA with duration of 0.5 ms at 4 Hz for 5 min. PVN was stimulated by electrical current pulses of 0.3 mA with duration of 0.5 ms at 80 Hz for 10 sec.</p><p><b>RESULT</b>Electrical stimulation of PVN increased mean arterial pressure. Stimulation of DPN significantly inhibited the pressor response induced by stimulation of PVN (P<0.01), with the inhibitory percentage of 43.27%. Microinjection of L-NAME (0.5 mol/L,10 microl) into the lateral ventricle of brain attenuated the inhibitory effect of DPN. The inhibitory percentage decreased from 47.73% to 12.49% (P<0.05). Microinjection of L-NAME (2 mol/L,100 nl) into amygdala reduced the inhibitory effect of DPN. The inhibitory percentage of stimulating DPN on the pressor response decreased from 50.71% to 25.30% (P<0.05).</p><p><b>CONCLUSION</b>Nitric oxide in the brain and amygdala are involved in the inhibitory effect of somatic afferent input on central pressor response.</p>