Effects of catecholamines on electrical and mechanical activities of the pregnant mouse myometrium.

1. The effect of catecholamines (adrenaline, noradrenaline, and isoprenaline) in combination with ƒ¿and ƒÀ-blocking agents (phentolamine and propranolol) on pregnant mouse myometrium was investigated. The catecholamines had an inhibitory action in this tissue, the minimal dose required to produce inhibition being 3•~10-9 (g/ml) for isoprenaline, <10-7 for adrenaline, and <10-6 for noradrenaline. While ƒÀ-adrenergic blocking agent antagonized the inhibitory action of the catecholamines, ƒ¿ -blocking agent did not. 2. Catecholamines produced a hyperpolarization of the membrane and hence spontaneous activity was inhibited. External current stimulation