Role of a-SNAP in Promoting Efficient Neurotransmission at the Crayfish Neuromuscular Junction

He, Ping, R. Chase Southard, Dong Chen, S. W. Whiteheart, and R. L. Cooper. Role of a-SNAP in promoting efficient neurotransmission at the crayfish neuromuscular junction. J. Neurophysiol. 82: 3406–3416, 1999. In this manuscript, we address the role of the soluble N-ethylmaleimide sensitive factor attachment protein (aSNAP) in synaptic transmission at the neuromuscular junction of the crayfish opener muscle. Immunochemcial methods confirm the presence of a-SNAP in these preparations and show that it is concentrated in the synaptic areas. Microinjection and electrophysiological studies show that a-SNAP causes an increase in neurotransmitter release yet does not significantly affect the kinetics. More specific quantal analysis, using focal, macropatch, synaptic current recordings, shows that a-SNAP increases transmitter release by increasing the probability of exocytosis but not the number of potential release sites. These data demonstrate that the role of a-SNAP is to increase the efficiency of neurotransmission by increasing the probability that a stimulus will result in neurotransmitter release. What this suggests is that a-SNAP is critical for the formation and maintenance of a “ready release” pool of synaptic vesicles.