Involvement of protein kinase C in muscarinic agonist-induced contractions of guinea pig ileal longitudinal muscle.

1. Carbachol (10(-5) M) caused an initial transient contraction (phasic contraction) and a subsequent late contraction (tonic contraction) in the guinea pig ileum. The phasic contraction was markedly suppressed by calmodulin antagonist W-7, but not by protein kinase C inhibitor H-7. 2. The tonic contraction was suppressed by H-7, but not by W-7. 3. The carbachol-induced phasic contraction in the absence of extracellular Ca2+ was suppressed by both W-7 and H-7. 4. Carbachol (10(-5) M) stimulated the formation of inositol phosphates (IPs) in the guinea pig ileum. The carbachol-induced IPs formation was dependent on the extracellular Ca2+ concentration.