Inhibitory alpha-adrenergic action of phenylephrine in guinea pig taenia caecum

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Abstract
Phenylephrine, a selective .alpha.-adrenergic stimulant, caused a maximal relaxation of the tenia from guinea pig cecum in a concentration of 10-6 g/ml. Phenylephrine did not influence intracellular cyclic[c]AMP and cGMP levels. Phenylephrine abolished the spontaneous spike discharge but no change was detected in 45Ca-uptake and 45Ca-efflux on the tissue level after phenylephrine. Ca-uptake and Ca-release on the subcellular level were not influenced by phenylephrine. Phenylephrine in Ca free-solution inhibited the response to CaCl2. Phenylephrine increased 42K-efflux in the normally polarized tenia and in the K-depolarized tenia.