Differential modulation of sympathetic and respiratory activities by cholinergic mechanisms in the nucleus of the solitary tract in rats.

Exp Physiol. 2014 Apr 11. [Epub ahead of print] Furuya WI, Bassi M, Menani JV, Colombari E, Zoccal DB, Colombari DS. I chose this paper because it was another relevant and recent one from my EB mentor, Debora Colombari. In it, they looked at the contributions of ACh signaling in the intermediate NTS (iNTS) and the caudal NTS (cNTS) to the phrenic nerve activity (PNA) and sympathetic nerve activity (SNA; thoracic sympathetic chain), with an emphasis on the NTS's roles in the baroreflex and peripheral chemoreflex. They found that injecting ACh into the iNTS inhibited SNA and PNA, but injections into the cNTS increased PNA without changing mean SNA (though it did change the pattern). Non-selective blockade of ACh receptors with mecamylamie (but not muscarinic blockade with atropine) in the iNTS blocked the ACh-induced effects on SNA and PNA. These blockades in the iNTS could also not alter baro- and chemoreflexes - so these must have been nicotinic-mediated effects. The cNTS was a little more complicated in that non-selective ACh blockade aboloshed the effect of ACh, but muscarinic blockade only reduced it - suggesting both receptor types are involved. However, PNA chemoreflex responses were reduced by mecamylamine but not atropine. The take-home message here is that different subnuclei of the NTS contribute differently to chemo- and baroreflexes, and that the NTS contributes to chemoreflex mainly through nicotinic activation. -DH