Lesions of the commissural nucleus of the solitary tract reduce arterial pressure in spontaneously hypertensive rats

It has been suggested that increased sympathetic activity and arterial chem oreceptors are important for the high blood pressure in spontaneously hyper tensive rats (SHR). Electrolytic lesions of the commissural nucleus of the solitary tract (commNTS) abolish (1) the cardiovascular responses to chemor eflex activation with potassium cyanide (KCN) in normotensive rats and (2) the hypertension that follows acute aortic baroreceptor denervation in rats . Therefore, in this study we investigated the effects of electrolytic lesi ons of the commNTS on basal mean arterial pressure (MAP), baroreflex, and c hemoreflex in SHR and in normotensive control Wistar-Kyoto (WKY) and Wistar rats. CommNTS lesions elicited a dramatic fall in MAP to normal levels dur ing the period Of Study (from the first to fourth day following lesions) in SHR and almost no changes in WKY and Wistar rats. The pressor responses to chemoreflex activation with KCN tested in the days 1 and 4 after commNTS l esions were abolished in SHR and in normotensive strains. The reflex tachyc ardia induced by sodium nitroprusside was also attenuated in days 1 and 4 a fter commNTS lesions in SHR, WKY, and Wistar rats. The data suggest that th e integrity of commNTS is important for the maintenance or high blood press ure in SHR and for the reflex responses dependent on sympathetic activation either in SHR or in normotensive strains.