[Biophysical properties of elastic artery smooth muscle]

The electrical and contractile responses of smooth muscle cells of the rabbit a. pulmonalis and pigeon a. carotis were investigated using extracellular stimulation through sucrose gap and intracellular recording of electrotonic potentials at different distances from the sucrose partitition. Neither spontaneous nor evoked electrical and contractile activities were registered in normal Krebs solution. Current-voltage relations of these muscle cells showed marked rectification. The amplitude of anelectrotonic potentials decreased exponentially with the distance from sucrose partitition, while the time to reach the half-amplitude of the electrotonic potentials was linear function of the distance. These facts indicate that cable equations can be applied to these muscles. The space constant calculated for the rabbit a. pulmonalis was equal to 1.2 mm and that for the pigeon a. carotis--to 1.0 mm. Results of these experiments strongly suggest the existence of low resistance pathways between arterial muscle cells.