생쥐 소장에서 배양된 Interstitial cells of cajal의 전기적 활동도에 대한 Carbachol의 조절

Abstract

Interstitial cells of cajal (ICC) are pacemaker cells that activate the periodic spontaneous inward currents (pacemaker currents) responsible for the production of slow waves in gastrointestinal smooth muscles. The effects of carbachol on the pacemaker currents in cultured ICC from murine small intestine were investigated by using whole-cell patch-clamp techniques at a holding potential of -70 mV (equilibrium potential of Cl^(-)) and at 30 ℃. Tetrodotoxin, nifedipine, tetraethylammonium, 4-aminopyridine, or glibenclamide did not change the frequency and amplitude of pacemaker currents. CsCl or LiCl instead of NaCl also produced pacemaker currents. However, divalent cations (Ni^(2+), Cd^(2+), Mn^(2+), and Co^(2+)) except Ba^(2+), nonselective cation channel blockers (gadolinium and flufenamic acid), external Ca^(2+)-free solution, and a reduction of external Na^(+) from normal to 1 mM inhibited pacemaker currents indicating that nonselective cation channels are involved in their generation. Carbachol depolarized the membrane potential in current clamp mode and produced tonic inward pacemaker currents. Muscarinic M_(2) and M_(3) receptor antagonist (methoctramine and 4-DAMP), intracellular GDPβs blocked these carbachol-induced responses. However, GTPγS produced tonic inward currents mimicked those of carbachol. Carbachol continued to produce tonic inward currents in external Ca^(2+)-free solution or in the presence of chelerythrine, a protein kinase C inhibitor. However, carbachol-induced tonic inward currents were blocked by cyclopiazonic acid, a Ca^(2+)-ATPase inhibitor in the endoplasmic reticulum or by an external 1 mM Na^(+) solution, or by flufenamic acid. These results demonstrate that carbachol may modulate intestinal motility by acting on ICC by activating nonselective cation channels via the release of intracellular Ca^(2+) induced by muscarinic M_(3) and M_(2) receptor stimulation.