TY - JOUR T1 - Phasic and tonic components in 5-HT2 receptor-mediated rat aorta contraction: participation of Ca++ channels and phospholipase C. JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 442 LP - 446 VL - 234 IS - 2 AU - T Nakaki AU - B L Roth AU - D M Chuang AU - E Costa Y1 - 1985/08/01 UR - http://jpet.aspetjournals.org/content/234/2/442.abstract N2 - The mechanisms of 5-hydroxytryptamine (5-HT)-induced contraction of rat aorta were investigated in vitro. The 5-HT-induced contraction could be analyzed into two distinct components (phasic and tonic) by the use of appropriate inhibitors; nifedipine, an inhibitor of voltage-dependent Ca++ channels, inhibited only the phasic component of 5-HT-induced contraction while totally blocking the KCl-induced contraction. 2-Nitro-4-carboxyphenyl-N,N-diphenylcarbamate, an inhibitor of phospholipase C, inhibited the tonic components of 5-HT-induced contraction as well as the 5-HT-induced stimulation of phosphoinositide hydrolysis in rat aorta. This component of contraction was mimicked by a protein kinase C activator 12-O-tetradecanoylphorbol-13-acetate. These results suggest that 5-HT2 receptors differentially regulate a voltage-dependent Ca++ channel and phospholipase C activity; the voltage-dependent Ca++ channel is involved in the phasic component of contraction whereas the phosphoinositide hydrolysis that results in the activation of protein kinase C and calcium mobilization by inositol triphosphate plays a physiologically important role in the tonic component of the aortic contraction. ER -