Distribution of the perivascular nerve Ca²⁺ receptor in rat arteries

Abstract

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-linked 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 were studied. Immunocytochemical analysis was performed using anti-CaR and anti-neural cell adhesion molecule (NCAM) antibodies. Wire myography was used to assess contracation and relaxation.

3. Although perivascular nerves of all arteries stained for CaR protein, there were regional differences. A morphometric method used to estimate CaR positive nerve density revealed the following rank order: mesenteric branch artery>basilar artery=renal interlobar artery>main renal trunk artery>left anterior descending coronary artery.

4. Vessels from the mesentery, renal, coronary, and cerebral circulations showed nerve-dependent relaxation in response to electrical field stimulation (EFS) when precontracted with serotonin in the presence of guanethidine. The degree of Ca²⁺-induced relaxation of mesenteric, renal, and cerebral arteries positively correlated with the magnitude of EFS-induced relaxation. In contrast, coronary arteries contracted at Ca²⁺ levels between 1.5 and 3 mmol 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 is present to varying degrees in the mesenteric, renal, and cerebral circulations, but only to a very limited extent in the coronary circulation.

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