The sympathetic control of blood pressure

Patrice G. Guyenet Nat Rev Neurosci. 2006 May; 7(5):335-46 I’ve been writing my introduction and figured this paper would be a great resource, so I read it *again*…………… The overall purpose of this review is to examine sympathoregulation and how altered sympathoexcitation can result in hypertension and other cardiovascular diseases. It is also important to mention that while SNA has been correlated to CVD, there are likely other mechanisms involved in the development of CVD, including hypertension. Apparently renal SNA is selectively regulated by volume receptors whereas the other sympathetic nerves are not. Also the rostral ventromedial medulla (RVMM) and medullary raphe are involved in cutaneous circulation, whereas the rostral ventrolateral medulla (RVLM) is not. I also did not know that the C1 neurons were only one of three clusters of adrenaline-synthesizing cells in the CNS, which is particularly interesting because we still don’t particularly know the role that adrenaline synthesis is even having in the RVLM, aside from being a good marker. Here are C1 cells that are non-barosensitive that control adrenaline-releasing chromaffin cells. Guyenet mentions that the baroreflex can be set (towards a higher level) in the case of different activities that require heightened sympathetic tone, exercise for example. I do not know the mechanism by which the baroreflex can be altered; I know that reflexes like the muscle metaboreflex exist and different types of hypoxia can raise blood pressure above baroreflex regulation. Something interesting, which is slightly unrelated (however mentioned in the review), is that obstructive sleep apnea (OSA) increases SNA throughout the waking period of the day, which I thought was surprising because I figured it would only have an effect during the night. Something that I found particularly interesting (as well as something that I don’t necessarily agree with) is the remark that “sympathetic efferents that innervate the kidneys are commonly presented as the only ones that are capable of influencing 24-h average BP.” I don’t think that renal controlling neurons are the only neurons involved in tonic cardiovascular regulation, I think that looking at only the neurons controlling the kidneys is totally short sighted. It would be interesting to look at a review with a similar approach as this, but considering all of the papers presented after 2006 as well. -MTL