Synapse turnover: the formation and termination of transient synapses.

Abstract

Neurons dissociated from chick embryo retina formed synapses with cultured rat striated muscle cells in 35-90 min when neurite extension was uncoupled from later steps in synapse formation. Apparently a reaction is required for synapse formation after neurons adhere to muscle cells. All synapses between retina neurons and muscle cells were terminated in 3-10 days depending on the developmental age of the neurons. The half-lives of synapses between muscle cells and retina neurons from 8, 12 or 13 day embryos were 36, 26 and 5 h and mean synapse life-times were 53, 37 and 7.1 h, respectively. The results showed that synapses turn over and that the rate of turnover increased during development. Apparently synapse formation and termination rates are regulated, and the specificity of synaptic connections may be increased by selective termination of synapses.