Contractions Of Smooth Muscle Strips Research Articles

Effects of a new cholecystokinin antagonist (GE 410) on the smooth muscle of the guinea pig ileum

Suc-Tyr-(SE)-Met-Gly-Trp-Met-Asp-beta-phenethylamide (GE 410) competitively antagonized the contractions of smooth muscle strips from guinea pig ileum (pA2 = 7.6, n = 0.95) induced by cholecystokinin-octapeptide (CCK8). GE 410 inhibited the electrically-induced cholinergically mediated contractile responses and the [3H]ACh release in the ileum, as well as the CCK-stimulated electrical contractile responses and the [3H]ACh release in the cholinergic nerve terminals. The results suggest the existence of CCK-receptors not only in the smooth muscles but also on the neurons.

Receptor-coupled, Permeabilized Smooth Muscle: Role of the phosphatidylinositol cascade, G-proteins, and modulation of the contractile response to Ca2+

Abstract alpha-Adrenergic (phenylephrine) and muscarinic (carbachol) agonists and inositol 1,4,5-trisphosphate caused calcium release and contractions in smooth muscle strips permeabilized with Staphylococcus aureus alpha-toxin. The responses to phenylephrine and carbachol required or were potentiated by added GTP and could be inhibited by GDP beta S. GTP and phenylephrine also increased the contractile response of permeabilized portal vein smooth muscle to cytoplasmic Ca2+. We conclude that while the G-protein-coupled phosphatidylinositol cascade, through inositol 1,4,5-trisphosphate-induced calcium release, is a major mechanism of pharmacomechanical coupling, a second G-protein-mediated pathway that modulates the calcium sensitivity of the regulatory contractile proteins also exists.