Somatosensory influences on renal sympathetic nerve activity in anesthetized Wistar and hypertensive rats

This study compared the cardiovascular and renal nerve activity responses to somatosensory stimulation with capsaicin in normotensive and hypertensive rats. The importance of the cardiopulmonary receptors in these two states was examined with the use of phenylbiguanide (PBG) infusion. Subcutaneous capsaicin increased blood pressure (BP), heart rate (HR), and renal nerve activity (RNA) 6-35% (P < 0.01), and total power (TP) and %power at HR (%PHR) rose two- to threefold (P < 0.001). PBG reduced basal RNA, TP, and %PHR (20-70%, P < 0.05). PBG did not change the cardiovascular, but attenuated the TP and %PHR increases due to capsaicin (P < 0.001-0.01). PBG given to vagotomized normotensive rats normalized the cardiovascular and RNA responses to capsaicin. In hypertensive rats, capsaicin increased BP, HR, RNA(10-20%), TP, and %PHR (50-70%, P < 0.001). PBG infusion into hypertensive rats decreased RNA (20%, P < 0.01) and the capsaicin-dependent rise in RNA was smaller (P < 0.05). TP and %PHR were unchanged, except in vagotomized hypertensive rats given PBG, in which these responses were minimally affected. Somatosensory modulation of RNA power spectra was suppressed by the cardiopulmonary receptors in normotensive rats, but in hypertensive rats their impact was much smaller.