Biophysical Effects of Adrenaline on the Smooth Muscle of the Rabbit Common Carotid Artery

Effects of adrenaline on the smooth muscle of the rabbit common carotid artery were studied by the partitional chamber method. The experiments on excitation-contraction coupling were carried out in isotonic Krebs solution; the other experiments were carried out in hypertonic Krebs solution. Adrenaline (10^-7 g/ml) caused rhythmical electrical and mechanical activity of arterial strips in isotonic Krebs solution. By addition of adrenaline (10^-5 g/ml), the membrane was depolarized by about 10 mv and the amplitude of the electrotonic potential was decreased by 40–50% of the control in hypertonic Krebs solution. Present experimental results suggest that the depolarization of the membrane and the decrease of the amplitude of the electrotonic potential in the artery are due to the increase of Na and Cl conductance. Contraction appeared in all preparations exposed to 10^-8 g/ml adrenaline; at that concentration membrane potential and membrane resistance showed little or no change.