Synaptic junctions in the cat spinal ganglion.

The cervical dorsal root ganglia (C5-C8) of the cat were examined in vivo with an electron microscope. Cell processes of unknown origin were observed to invade the area between the satellite cell sheaths and the ganglion cells, and their terminals were found to be in synaptic contact with the soma of the ganglion cells. Like chemical synapses, these synapses are numerous, containing small and round vesicles and mitochondria in the presynaptic terminals and the asymmetrical membrane thickening. The postsynaptic membrane was thicker than the presynaptic one. These presynaptic terminals were surrounded by the satellite cell sheaths. The present study strongly suggested the presence of at least a few chemical synapses, especially axosomatic synapses, in the cat spinal ganglion.