Fenamates Potentiate the α₁-Adrenoceptor-Activated Nonselective Cation Channels in Rabbit Portal Vein Smooth Muscle

Abstract

The agonistic action of fenamates on the α₁-adrenoceptor-activated cationic current (I_cat) in rabbit portal vein smooth muscle was investigated with the whole-cell patch clamp technique. At −50 mV, the fenamates (100-500 μM) increased I_cat dose-dependently, up to several fold. This increase was not accompanied by changes in the reversal potential and strongly inhibited by 500 μM Cd²⁺ or 10 mM procaine. The enhancing effect of fenamates was also observed on the cationic current activated by intracellularly applied GTPγS. These results suggest that fenamates may be useful as a new class of activator for receptor-operated cation channels in smooth muscle.