Observations of impaired autonomic regulation of arterial pressure in obese Zucker rats: focus on changes in the nucleus of the solitary tract.

Like obese humans, obese Zucker rats (OZR) develop hypertension and impaired baroreflexes. In adult OZR, brainstem nucleus tractus solitarius (NTS) becomes less responsive to baroreceptor inputs. We hypothesized NTS neurons of male OZR undergo abnormal neuroplasticity (ΔFosB expression) versus lean Zucker rats, and these changes would be absent in females with normal baroreflexes. We saw increased NTS ΔFosB at 7-8 wks in male but not female OZR. Unlike male OZR, females had normal baroreflexes and NTS function. We were unable to identify the NTS neurons with ΔFosB. They do not project to caudal ventrolateral medulla (baroreflex pathway), are not A2 neurons, and do not make nitric oxide. These data suggest the NTS of male OZR undergoes abnormal neuroplasticity with the onset of cardiovascular deficits and females are protected. Future studies will identify the NTS neurons and determine what causes changes in them to contribute to impaired cardiovascular regulation in OZR.