Commissural NTS lesions and cardiovascular responses in aortic baroreceptor-denervated rats

Both acute (1 day) lesions of the commissural nucleus of the solitary tract (commNTS) and aortic baroreceptor denervation increase presser responses t o bilateral common carotid occlusion (BCO) during a 60-second period in con scious rats. In this study, we investigated the following: (1) the effects of commNTS lesions on basal mean arterial pressure (MAP) and heart rate (HR ) of aortic denervated (ADNx) rats; (2) the effects of acute commNTS lesion s on presser responses to BCO in ADNx rats; and (3) the effects of chronic (10 days) commNTS lesions on the presser response to BCO, ADNx increased ba sal MAP and HR in sham-lesioned rats. Acute commNTS lesions abolished the M AP and HR increases observed in ADNx rats. Acute commNTS lesions increased the presser responses to BCO in rats with intact-baroreceptor innervation b ut produced no additional change in the presser response to BCO in ADNx rat s. Chronic commNTS lesions did not change the presser responses to BCO in r ats with intact-baroreceptor innervation. The data shaw that acute commNTS lesions abolish the MAP increase produced by aortic baroreceptor denervatio n. They also suggest that acute commNTS lesions enhance the presser respons e to BCO by partial withdrawal of aortic baroreceptor inputs into the NTS. Chronically, reorganization in the remaining aortic baroreceptor or in the baroreflex function as a whole might produce normalization of the cardiovas cular responses to BCO.