Spontaneous synaptic potentials and quantal release of transmitter in the stellate ganglion of the squid

Abstract

Several kinds of synapses have been studied in the stellate ganglion of the squid. A small electric coupling was found between giant fibers in different stellar nerves. Post-synaptic potentials recorded from the cells of small axons are composite, indicating that there are converging inputs from several preganglionic fibers. Spontaneous miniature synaptic potentials were recorded from all types of synapses. Miniature potentials in the cells of small axons had a slower time course than those in the giant fiber system. Tetrodotoxin abolished nerve impulses in the ganglion but did not prevent the spontaneous quantal release of transmitter from the terminals, or its action on the post-synaptic membrane; nor did it prevent the increase in rate of release produced by depolarization of the presynaptic fibre. Glutamate depolarized the giant fiber when applied iontophoretically to the synaptic region. Similar doses applied intracellularly were without effect.