Plasticity in the central nervous system: do synapses divide?

Abstract

Changes in the proportion of synapses containing postsynaptic densities with perforations during periods of increased synapse formation have led to a hypothesis describing a possible division of preexisting synapses. Relevant features of this model are that various types of stimulation result in the following sequence of events: the synaptic junction increases in area; a perforation forms in the enlarging synaptic junction; a synaptic spinule appears apposed to the perforation in the postsynaptic density; the perforation in the synaptic junction increases in size until the synaptic junction splits into 2 separate synaptic junctions within the same synaptic terminal; and the dendritic spine divides into 2, each containing a synaptic junction. Physiological responses in which synapse division may possibly play a role include hormone-induced neuronal changes, reinnervation of dendrites after lesions and learning and memory.