Paraventricular nucleus control of blood pressure in two-kidney, one-clip rats: effects of exercise training and resting blood pressure.

Rossi NF, Chen H, Maliszewska-Scislo M. Paraventricular nucleus control of blood pressure in two-kidney, one-clip rats: effects of exercise training and resting blood pressure. Am J Physiol Regul Integr Comp Physiol 305: R1390–R1400, 2013. First published October 2, 2013. Background: This is a paper from Dr. Rossi's laboratory which I believe is the first publication from her lab in which they look at the influence of chronic wheel running versus sedentary conditions. They examine both tonic GABA and nitric oxide signaling in the paraventricular nucleus of the hypothalamus (PVH, as opposed to the paraventricular nucleus of the thalamus). They record mean arterial pressure (MAP), plasma angiotensin II (Ang II) and renal sympathetic nerve activity (RSNA) in conscious normotensive Sprague-Dawley rats versus their two kidney, one clip model of hypertension (also Sprague-Dawleys) after 6 or 12 weeks of wheel running or sedentary conditions. The impressive thing about this study is the fact that it is done in conscious animals with RSNA and PVN microinjections in normotensive and hypertensive animals after six or 12 weeks of wheel running. A technical tour de force as they say. Results: MAP and Ang II were higher in HTN rats which were both reduced similarly by wheel running both at 6 and 12 weeks of running. HTN rats also had lower pressor and sympathoexcitatory responses to blockade of nitric oxide or GABA in the PVH which were attenuated by wheel running. Interestingly, in the most hypertensive animals (i.e. those >180 mmHg) there was very little change in response to bicuculline and in fact, in animals above 200 mmHg, decreases in arterial pressure in response to bicuculline were observed. These novel findings suggest that GABA provides a basal level of excitation through ill-defined neuroplastic changes in the most hypertensive animals. Conclusions: I thought this was not only an amazing paper technically but also very interesting to our laboratory because it involved wheel running; conscious microinjections into PVH, a brain region that projects directly to RVLM; and had measurements of conscious sympathetic nerve activity. It's a good read and a very good candidate for a future journal club if anyone with an interest in PVH, exercise and SNA. ;-) ~PJM