Role of Myogenic Propagation in Vascular Smooth Muscle Response to Vasomotor Nerve Stimulation

Innervated preparations of the spontaneously active vascular smooth muscle of the rat portal vein were used for the present study. The preparation was so arranged as to allow blockade of myogenic conduction between two adjacent portions. It was also possible to subject one of the portions selectively to adrenergic receptor blockade. It could be shown that myogenic propagation is necessary for coordination of the neurogenic contractile response, as is the case with the synchronization of the spontaneous myogenic activity. Moreover, after the direct response to noradrenaline and adrenergic nerve stimulation had been blocked in one portion of the muscle selectively, its activity was still enhanced during nerve stimulation by means of a myogenic spread of excitation from the other portion, where the innervation and adrenergic receptor function were intact. It is concluded that myogenic conduction contributes to the effectiveness of neurogenic activation by coordinating the contractions and by recruiting non‐innervated muscle cells to participate in the response. The results are discussed in relation to the sparse innervation described in vascular smooth muscle.