[Ultrastructural features of gap junction type synapses in the motor nuclei of the frog spinal cord].

Ultrastructure of synapses in motor nuclei of the frog spinal cord has been studied electron microscopically. In the area examined, synapses with chemical and electrotonic means of transmission have been revealed. Synapses of a gap junction type formed by an intimate contact between plasmic membrane of neuronal processes or axonal terminals and dendrite (pericaryon) of motorneuron can serve as a morphological substrate for electrotonic transmission. Several types of electrotonic synapses have been determined: dendro-dendritic, dendro-somatic, axodendritic, axosomatic and axoaxonic.