Syncytial cytoplasmic anastomoses between neurites in caudal mesenteric ganglion cells in adult cats.

The fact that most published data on syncytial cytoplasmic anastomoses are based on the autonomic nervous system in the early postnatal period of development, when many nerve fibers are poorly ensheathed by glia or have no glial sheaths at all, has led to the assumption that these anastomoses do not exist in adults because of the significant development of the glia and glial insulation of individual neurites from each other. We tested this assumption using electron microscopic studies of the caudal mesenteric ganglion in adult cats. A high level of glial ensheathing of neurites was observed. However, syncytial pores were seen between contacting neurites lacking glial sheaths in almost every specimen. This is the first report describing axodendritic synapses with perforations in the presynaptic zone outside the synaptic specializations in the autonomic nervous system. It is suggested that although syncytial cytoplasmic connections are seen in adult animals, they do not contradict the neuron theory.