Proton Acts as a Neurotransmitter for Nicotine-Induced Adrenergic and Calcitonin Gene-Related Peptide-Containing Nerve-Mediated Vasodilation in the Rat Mesenteric Artery

Abstract

Nicotine stimulates presynaptic nicotinic acetylcholine receptors in perivascular adrenergic nerves and releases unknown transmitter(s) that activate transient receptor potential vanilloid-1 (TRPV1) located on calcitonin gene-related peptide (CGRP)-containing (CGRPergic) nerves, resulting in vasodilation. The present study investigated a potential transmitter transmitting between perivascular adrenergic nerves and CGRPergic nerves. Rat mesenteric vascular beds without endothelium were contracted by perfusion with Krebs' solution containing methoxamine, and the perfusion pressure and pH levels of the perfusate were measured. Nicotine perfusion for 1 min induced concentration-dependent vasodilation and lowered pH levels, which were abolished by cold-storage denervation of preparations, guanethidine (adrenergic neuron blocker), and mecamylamine (nicotinic ␣ 3 ␤ 4 -acetylcholine receptor antagonist). Capsazepine (TRPV1 antagonist) blunted nicotine-induced vasodilation, but had no effect on the reduction of pH. Injection of hydrochloric acid (HCl) and perfusion of Krebs' solution at low pH (6.0 -7.2) induced vasodilation. HClinduced vasodilation was inhibited by cold-storage denervation, capsazepine, capsaicin (CGRP depletor), and CGRP(8 -37) (CGRP receptor antagonist). Perfusion of adrenergic transmitter metabolites (normetanephrine and 3-methoxydopamine), but not of other metabolites, induced vasodilation, which was not inhibited by capsaicin treatment. Immunohistochemical staining of mesenteric arteries showed dense innervation of CGRP-and TRPV1-immunopositive nerves, with both immunostainings appearing in the same neuron. Mesenteric arteries were densely innervated by neuropeptide Y-immunopositive nerves, which coalesced with CGRP-immunopositive nerves. Scanning and immunoscanning electron microscopic images showed coalescence sites of different perivascular fibers before they intruded into smooth muscles. These results indicate that nicotine initially stimulates adrenergic nerves via nicotinic ␣ 3 ␤ 4 -receptors to release protons and thereby induces CGRPergic nerve-mediated vasodilation via TRPV1.It is widely accepted that vascular tone is maintained mainly by sympathetic adrenergic nerves via the release of the neurotransmitter norepinephrine. However, accumulating evidence reveals that nonadrenergic, noncholinergic (NANC) vasodilator nerves also play a role in regulation of vascular tone. We have demonstrated that the rat mesenteric artery has dense innervation of calcitonin gene-related peptide (CGRP)-containing (CGRPergic) nerves that release a transmitter, CGRP, causing vasodilation (Kawasaki et al., 1988). Recently, we reported that nitric oxide (NO)-containing nerves innervating rat mesenteric arteries are involved in modulation of adrenergic neurotransmission (Hatanaka et al., 2006). The rat mesenteric artery is also densely innervated by adrenergic nerves, which contain the main neuro-

Neurogenic Vascular Responses in Male Mouse Mesenteric Vascular Beds

“…9), suggesting that sympathetic adrenergic nerves innervate the male mouse mesenteric perivascular nerves, like in male rat mesen- teric arteries. These findings obtained from male mouse mesenteric vascular beds are in good accordance with previous reports in male rat mesenteric vascular beds (4, 13,15,21). It is also likely that TH-immunopositive nerves innervating the small arteries are responsible for the neurogenic vasoconstrictor response.…”

“…It appears that the PNS-induced vasoconstrictor response is neurogenic in nature. Furthermore, the adrenergic neuron blocker guanethidine, which blunts the neurogenic release of the adrenergic neurotransmitter norepinephrine (13), abolished the PNS-induced vasoconstrictor response, suggesting that the sympathetic adrenergic nerve mediates the neurogenic vasoconstriction. Furthermore, the present immunohistochemical study demonstrated male mouse mesenteric arteries and veins to be densely innervated by adrenergic TH-immunopositive nerve fibers, which were sensitive to the adrenergic toxin 6-OHDA, but not capsaicin (Fig.…”

Pharmacodynamic Characterization of Nitric Oxide-Mediated Vasodilatory Activity in Isolated Perfused Rat Mesenteric Artery Bed

“…10,12) After being anesthetized with sodium pentobarbital (50 mg/kg, intraperitoneally (i.p. )), each rat was fixed on its back, and a middle incision was gently made in the abdomen, exposing the jejunum and superior mesenteric artery.…”

“…Nitric oxide (NO), acetylcholine (ACh), and sodium nitroprusside (SNP) were selected as model vasodilators due to their well-known pharmacological characteristics. 6,7,9,10) In addition, they involve a common process to exert vasodilatory activity. NO acts as an endothelium-derived relaxing factor, 6,11) stimulating soluble guanylate cyclase to promote cGMP production from GTP.…”

Adrenergic Stimulation–Released Histamine Taken-up in Adrenergic Nerves Induces Endothelium-Dependent Vasodilation in Rat Mesenteric Resistance Arteries

“…In rat perfused mesenteric vascular beds with active tone, PNS has been shown to produce an initial vasoconstriction followed by a long-lasting vasodilation (11). Since guanethidine abolished the PNS-induced vasoconstriction ( Fig.…”