Experimental Modeling and Discussion of Syncytial Connections in the Nervous System

This article addresses the question of the possible existence of syncytial connections in the nervous system by presenting the first data on experimental syncytial fusion of neurons. Neurons from the ganglia of the mollusk Lymnaea stagnalis without their surrounding glial cells, isolated using pronase, were brought together by centrifugation and remained in the aggregated state for two days in culture medium. The neurons retained the ability to form normal processes. At the boundaries of adjacent cells, contacting mutual invaginations (podia) appeared, separated from each other by vacuole-like enlargements of intercellular clefts. Electron microscopy showed that the outer cell membranes were disrupted at contact sites between podia. Only residual fragments of degraded membrane were seen. The cytoplasm of one adjacent cells merged continuously with the cytoplasm of the other. Thus, these experiments provide further support for the cellular theory in relation to the common main properties of all cells and extend the view of the neuron theory that the nervous system, apart from chemical synapses and electrical membrane contacts, may also include syncytial interneuron contacts.