| Effect of Ca2+ on contractile responses induced by perivascular nerve stimulation in isolated coronary artery of pig |
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Yong-geun Hong1, Cheol-soo Shim2, Joo-heon Kim3 |
1Department of Biochemistry, College of National Science, Gyeongsang National University
2Eastern Branch, Gyeongnam Livestock Promotion Institute
3College of Veterinary Medicine and Institute of Animal Medicine, Gyeongsang National University |
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| Abstract |
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The present study was performed to elucidate the effects of extracellular $Ca^{2+}$ on contractile responses in isolated porcine coronary artery ring using by perivascular nerve stimulation (PNS). Especially, the study was focused on the source of $Ca^{2+}$ on $P_{2X}$-purinoceptor mediated muscle contraction which one of $P_2$-purinoceptor subtypes. The following results can be drawn from these studies : 1. The phasic contractions induced by PNS were inhibited with muscarinic receptor antagonist, atropine ($10^{-6}M$). 2. The phasic contractions induced by PNS were significantly inhibited by sequential treatment with atropine and adrenergic neural blocker, guanethidine ($10^{-6}M$). 3. The phasic contractions induced by PNS were inhibited with $P_{2X}$-purinoceptor desensitization by repetitive application of $alpha$,$eta$-Me ATP ($10^{-4}M$). 4. The phasic contractions induced by PNS were so weakened in calcium-free medium. 5. The phasic contractions induced by PNS were inhibited with calcium channel blocker, verapamil ($10^{-6}{sim}5{ imes}10^{-6}M$). 6. The phasic contractions induced by PNS on pretreated with verapamil ($10^{-6}{sim}5{ imes}10^{-6}M$) were not changed by $alpha$,$eta$-Me ATP ($10^{-4}M$). These results demonstrate that the neurogenic phasic contractions induced by PNS are due to adrenergic-, cholinergic- and $P_{2X}$-purinergic receptors and the origin of $Ca^{2+}$ on $P_{2X}$-purinoceptor mediated muscle contraction is extracellular $Ca^{2+}$ through plasmalemmal $Ca^{2+}$ channels. |
| Key Words:
perivascular nerve stimulation, $Ca^{2+}$, $P_{2X}$-purinoceptor, coronary artery, pig |
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