Distribution of the perivascular nerve Ca2+ receptor in rat arteries

1 We recently showed that perivascular sensory nerves of mesenteric branch arteries express a receptor for extracellular Ca2+ (CaR), and reported data indicating that this CaR mediates relaxation induced by physiologic levels of Ca2+. We have now tested whether the perivascular sensory nerve CaR-lin ked dilator system is a local phenomenon restricted to the mesentery, or is present in other circulations. 2 Vessels from the mesenteric, renal, coronary, and cerebral circulations w ere studied. Immunocytochemical analysis was performed using anti-CaR and a nti-neural cell adhesion molecule (NCAM) antibodies. Wire myography was use d to assess contracation and relaxation. 3 Although perivascular nerves of all arteries stained for CaR protein, the re were regional differences. A morphometric method used to estimate CaR po sitive nerve density revealed the following rank order: mesenteric branch a rtery > basilar artery = renal interlobar artery > main renal trunk artery > left anterior descending coronary artery. 4 Vessels from the mesentery, renal, coronary, and cerebral circulations sh owed nerve-dependent relaxation in response to electrical held stimulation (EFS) when precontracted with serotonin in the presence of guanethidine. Th e degree of Ca2+-induced relaxation of mesenteric, renal, and cerebral arte ries positively correlated with the magnitude of EFS-induced relaxation. In contrast, coronary arteries contracted at Ca2+ levels between 1.5 and 3 mm ol L-1,and relaxed to a small degree to 5 mmol L-1 Ca2+. 5 Thus, a functional perivascular sensory nerve CaR-linked dilator system i s present to varying degrees in the mesenteric, renal, and cerebral circula tions, but only to a very limited extent in the coronary circulation.