The action of noradrenaline on single smooth muscle cells freshly dispersed from the guinea‐pig pulmonary artery

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Abstract
1 Responses to ionophoretically-applied noradrenaline were investigated with micro-electrodes in whole tissue preparations and with patch pipettes in isolated cells dispersed from the guinea-pig pulmonary artery. 2 In whole tissue and dispersed cells noradrenaline evoked monophasic depolarizations which had a similar time course. 3 In dispersed cells the amplitude of electronic potentials was reduced during the noradrenaline-evoked depolarization. Under voltage clamp noradrenaline elicited an inward current, which persisted in 18 mm external potassium with the membrane potential set at the potassium equilibrium potential. 4 In voltage clamp experiments the amplitude of current steps to hyperpolarizing voltage jumps was increased during the noradrenaline-induced inward current. These data suggest that the depolarization to noradrenaline in the guinea-pig pulmonary artery is mediated by an increase in membrane conductance.