title: Exogenous synapsin I promotes functional maturation of developing neuromuscular synapses.
abstract: We have investigated the possible role of synapsin I, a nerve terminal-specific protein, in the maturation of neuromuscular synapses in Xenopus cell cultures. Purified synapsin I was loaded into embryonic spinal neurons by injection of the protein into one of the early blastomeres of a Xenopus embryo. At synapses made by synapsin I-loaded neurons, spontaneous synaptic currents occurred with higher frequency and amplitude, and the amplitude exhibited an earlier appearance of a bell-shaped distribution. These characteristics are indicative of more mature quantal secretion. Impulse-evoked synaptic currents also showed a significant increase in amplitude. Using cell manipulation techniques, enhanced transmitter release from synapsin I-loaded neurons was shown to occur at the onset of synaptogenesis, suggesting a presynaptic developmental action of synapsin I prior to synaptic contact. Taken together, these results suggest that endogenous synapsin I may participate in the functional maturation of synapses.
authors.affiliation: Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, New York 10021.
authors.forename: B
authors.initials: B
authors.lastname: Lu
authors.forename: P
authors.initials: P
authors.lastname: Greengard
authors.forename: M M
authors.initials: MM
authors.lastname: Poo
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D004553:Electric Conductivity; D066298:In Vitro Techniques; D009469:Neuromuscular Junction / Q000254:growth & development*; D013569:Synapses / Q000502:physiology*; D016704:Synapsins / Q000378:metabolism*; D009435:Synaptic Transmission; D013997:Time Factors; D014982:Xenopus laevis / Q000196:embryology
chemical_list: D016704:Synapsins; D000109:Acetylcholine