Fig. 1. A model of signal transduction of acetylcholine-induced Ca²⁺sensitization in smooth muscle. Rho = monomeric G protein; ROK = rho-associated kinase; CaM = calmodulin; MLCK = myosin light-chain kinase; rMLC = regulatory myosin light chain; SMPP = smooth muscle protein phosphatase. Dashed lines indicate pathways that are of uncertain physiologic significance. Also shown is the putative site of halothane action and the actions of compounds used to perform MLCK and SMPP assays (wortmannin and microcystin-LR).