[Ultrastructure of interneuronal junctions in the superior cervical sympathetic ganglia of cats].

The structure of the synaptic contacts of the superior cervical sympathetic ganglion was studied both in intact cats and following the section of the cervical sympathetic nerve and removing the Th12, L1, L2 spinal ganglia. The analysis of degenerating synaptic terminals showed that most of them belong to the cervical sympathetic nerve axons. Some of such terminals remain intact and belong to another source. Certain part of dendro-dendritic and dendro-somatic contacts are formed by dendrites of the Th12, L1, L2 spinal ganglia neurons. It is supposed that the dendro-dendritic contacts could function as synapses. The dendro-dendritic contacts establish complexes consisting of an axon and several dendrites. Such complexes might be a substrate for ensuring the synchronization of the rhythmic neuronal activity in the cellular glomeruli of the ganglion. The discovered enlarged structures (from 6 to 20 microns in diameter) seem to represent receptor endings of afferent neurons of the spinal ganglia; these structures may establish synaptic contacts both with axon terminals and dendrites of the ganglionic neurons.