Some properties of the transmitter release mechanism at the rat ganglionic synapse during potassium stimulation.
In the present investigation a study has been made using intracellular recordings in the rat superior cervical ganglion of the mode of transmitter release induced by raised external potassium ion concentration (40 mM), after acetylcholine synthesis has been blocked by hemicholinium-3. It is shown that the progressive decline in the rate of acetylcholine output from the ganglion is related to a decrease in the number of quanta being released. Furthermore, under these conditions there is no evidence for a reduction in the size of the transmitter quantum. The statistical foundations of the quantal release process at the rat ganglionic synapse have been investigated by comparing the distribution of the number of miniature EPSPs during successive constant time intervals in the tracings with the corresponding Poisson and binomial predictions. Analyses have shown that the probability for a quantum to be released is so small as to produce a binomial distribution of responses indistinquishable fro- the corresponding Poisson distribution, both at the beginning of the potassium-induced quantum discharge and when transmitter release level is low after exhaustion of acetylcholine tissue content.
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D005071:Evoked Potentials; D005725:Ganglia, Autonomic / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008959:Models, Neurological; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D013569:Synapses / Q000378:metabolism*; D013570:Synaptic Membranes / Q000378:metabolism; D013997:Time Factors
D000109:Acetylcholine; D011188:Potassium