PHASIC AND TONIC COMPONENTS IN 5-HT2 RECEPTOR-MEDIATED RAT AORTA CONTRACTION - PARTICIPATION OF CA++ CHANNELS AND PHOSPHOLIPASE C-1

  • 1 January 1985
    • journal article
    • research article
    • Vol. 234  (2) , 442-446
Abstract
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 2 distinct components (phasic and tonic) by the use of appropriate inhibitors; nifedipine, an inhibitor of voltage-dependent Ca2+ 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. Apparently 5-HT2 receptors differentially regulate a voltage-dependent Ca2+ channel and phospholipase C activity; the voltage-dependent Ca2+ channel is involved in the phasic component of contraction the phosphoinositide hydrolysis that results in the activation of protein kinase C and Ca mobilization by inositol triphosphate plays a physiologically important role in the tonic component of the aortic contraction.

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