Cardiovascular and neuroendocrine responses to behavioral stress after central or peripheral barodenervation in rats.

The cardiovascular and neuroendocrine responses to acute behavioral stress were evaluated in rats after disruption of the baroreflexes by electrolytic lesions of the nucleus tractus solitarii (NTS) or sinoaortic denervation (SAD). Rats with NTS lesions or SAD showed significantly greater increases in mean arterial pressure (MAP) and plasma norepinephrine (NE) concentrations than control rats during a single 30-min escape-avoidance test. In addition, the increases in MAP and plasma NE concentration of NTS lesion rats were significantly greater than those of SAD rats. However, NTS lesion rats showed no increase in plasma renin activity (PRA), as observed in the other groups. Thus, disruption of the baroreflexes by NTS lesions or SAD augments the arterial pressure and plasma NE responses to stress. Additionally, NTS lesions appeared to eliminate the neurons or fibers of passage participating in the sympathetically mediated increase in PRA.