Effect of paraventricular nucleus lesions on arterial pressure and heart rate after aortic baroreceptor denervation in the rat.

Two series of experiments were done in male Wistar rats to investigate the effects of lesions of the paraventricular nucleus of the hypothalamus (PVH) on the maintenance and development of the elevated arterial pressure resulting from denervation of aortic baroreceptors. In the first series, after control recordings of arterial pressure (AP) and heart rate (HR), rats were subjected to either bilateral aortic depressor nerve (ADN) transection or sham-ADN transection. These animals were later subjected to either bilateral lesions of the PVH or sham-PVH lesions. AP (146 +/- 2 mm Hg) and HR (515 +/- 5 bpm) were significantly elevated in only the ADN-transected groups. Bilateral lesions of the PVH significantly reduced AP (119 +/- 3 mm Hg) and HR (440 +/- 8 bpm) in the ADN transected animals compared to ADN-transected sham-PVH-lesioned animals, to levels which were not significantly different from pre-ADN-transected levels (AP, 113 +/- 2 mm Hg; HR, 448 +/- 3 bpm), and from sham-ADN-transected PVH-lesioned (AP, 119 +/- 2 mm Hg; HR, 391 +/- 6 bpm) and sham-ADN-transected sham-PVH-lesioned animals (AP, 116 +/- 2 mm Hg; HR, 436 +/- 4 bpm). In the second series of experiments, after control AP and HR recordings rats were first subjected to either bilateral lesions of the PVH or sham-PVH lesions, and second to either bilateral ADN transection or sham-ADN transection. PVH lesions did not significantly alter the AP and HR from control levels.(ABSTRACT TRUNCATED AT 250 WORDS)