[Myoneural contacts in the frog bladder wall]

Ultrastructural interrelations of myocytes with efferent axons have been studied in the wall of the frog urinary bladder. Structural peculiarities of axons making contacts and of those not making contacts with smooth myocytes have been revealed. Two forms of the myoaxonal contacts have been discovered: without axon plunging into cytoplasm of the myocyte and with plunging into it. Both forms are organized either by a fasciculus of axons, or by single axons, and they innervate either single myocytes, or their group. Not more than 10% of myocytes get efferent innervation, others are not innervated. In composition of the myoneural contact certain active zones are found, however, they do not possess any specific signs of the synapse. A morphological type of axons has been determined; they are supposed to be processes of local (vesical) neurons and innervate myocytes of a peculiar processive form.