Serotonin contracts the rat mesenteric artery by inhibiting 4-aminopyridine-sensitive Kv channels via the 5-HT2A receptor and Src tyrosine kinase

Abstract

Serotonin (5-hydroxytryptamine (5-HT)) is a neurotransmitter that regulates a variety of functions in the nervous, gastrointestinal and cardiovascular systems. Despite such importance, 5-HT signaling pathways are not entirely clear. We demonstrated previously that 4-aminopyridine (4-AP)-sensitive voltage-gated K+ (Kv) channels determine the resting membrane potential of arterial smooth muscle cells and that the Kv channels are inhibited by 5-HT, which depolarizes the membranes. Therefore, we hypothesized that 5-HT contracts arteries by inhibiting Kv channels. Here we studied 5-HT signaling and the detailed role of Kv currents in rat mesenteric arteries using patch-clamp and isometric tension measurements. Our data showed that inhibiting 4-AP-sensitive Kv channels contracted arterial rings, whereas inhibiting Ca2+-activated K+, inward rectifier K+ and ATP-sensitive K+ channels had little effect on arterial contraction, indicating a central role of Kv channels in the regulation of resting arterial tone. 5-HT-induced arterial contraction decreased significantly in the presence of high KCl or the voltage-gated Ca2+ channel (VGCC) inhibitor nifedipine, indicating that membrane depolarization and the consequent activation of VGCCs mediate the 5-HT-induced vasoconstriction. The effects of 5-HT on Kv currents and arterial contraction were markedly prevented by the 5-HT2A receptor antagonists ketanserin and spiperone. Consistently, α-methyl 5-HT, a 5-HT2 receptor agonist, mimicked the 5-HT action on Kv channels. Pretreatment with a Src tyrosine kinase inhibitor, 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine, prevented both the 5-HT-mediated vasoconstriction and Kv current inhibition. Our data suggest that 4-AP-sensitive Kv channels are the primary regulator of the resting tone in rat mesenteric arteries. 5-HT constricts the arteries by inhibiting Kv channels via the 5-HT2A receptor and Src tyrosine kinase pathway.

Diverse effects of a 445 nm diode laser on isometric contraction of the rat aorta

“…Increased tyrosine phosphorylation is closely associated with VSM contraction. Src tyrosine kinase was reported to be a critical regulator of rat arterial vasocontraction [11,12]. The western blotting results in this study also showed that 445 nm laser irradiation induced phosphorylation of tyrosine residues in proteins, including those with the molecular weight of Src tyrosine kinase ( Fig.…”

“…To assess the contribution of VLCC-dependent and -independent regulation of 445 nm laser-induced changes in the contraction of VSM, 5-HT (instead of 35 mM KCl) was used for precontraction in some experiments. The 5-HT-induced VSM contraction was reportedly Src tyrosine kinase-dependent [11] and was composed of ~70% VLCC-dependent and ~30% VLCC-independent contractions [12,14]. Irradiation with the 445 nm laser initially relaxed endothelium-denuded aortic rings pre-contracted with 5-HT (10 μM), but was followed by contraction (Fig.…”

“…1(C) (see below). Tyrosine phosphorylation by protein tyrosine kinase (PTK) in vascular smooth muscles frequently mediated agonist-, oxidative stress-, and light irradiation-induced vasoregulation, which include vasocontraction [9][10][11][12]. In order to investigate the role of PTK in endothelium-denuded aortic rings, we examined the effects of a broad-spectrum PTK inhibitor, genistein.…”

NaHS induces relaxation response in prostaglandin F2α precontracted bovine retinal arteries partially via Kv and Kir channels

“…However, a nonspecific effect of 4-aminopyridine can be excluded, at least in the bovine retinal arteries, as previously documented that the relaxations to the directly acting vasodilator, sodium nitroprusside (SNP) were unaffected by 4-aminopyridine in this artery (Boussery et al, 2005). In addition, TEA does not always display identical properties with 4-aminopyridine in mediating the vasorelaxation (Novakovic et al, 2006) and regulating the vascular tone (Sung et al, 2013). Thus, this discrepancy is more likely to be related to the existance of different types of K v channel currents and the diverse sensitivities of 4-aminopyridine and TEA towards these currents.…”

Up-Regulation of the Voltage-Gated K_V2.1 K⁺ Channel in the Renal Arterial Myocytes of Dahl Salt-Sensitive Hypertensive Rats

“…34) This study showed that K V 2.1 inhibition-induced contractile responses were enhanced in the RAs of Dahl-HS. On the other hand, Song et al have shown that K V 2.1 activity is enhanced by Src-mediated phosphorylation in neurons.…”