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V Perri

Publications and source records attributed to V Perri.

At least 55 records · Page 3Linked to original sources
PubMed1976

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.

Acetylcholine↗
PubMed1973

Quantal mechanism of transmitter release during progressive depletion of the presynaptic stores at a ganglionic synapse. The action of hemicholinium-3 and thiamine deprivation.

In the present experiments we interfered with the mechanism of acetylcholine (ACh) synthesis in the rat superior cervical ganglion by impairing the supply of either the choline group (hemicholinium no. 3 [HC-3]treatment) or the acetyl group (thiamine deprivation). Under both conditions stimulation causes in the ganglion a progressive decline in ACh output associated with a depletion of transmitter tissue content. ACh release from the terminals of a single preganglionic fiber was estimated from the quantum content value of the evoked excitatory postsynaptic potentials (EPSP's) recorded intracellularly in the ganglion neuron under test. The present observations indicate that Poisson statistics describe transmitter release at either low or high release levels. Furthermore, the progressive decline in the rate of ACh output occurring during repetitive stimulation is shown to correspond to a progressive decrease in the number of transmitter quanta released per impulse and not to any modification in the size of individual quanta. Some 8,000 transmitter quanta proved to represent the presynaptic transmitter store initially present in those terminals on a neuron that are activated by stimulation of a single preganglionic fiber. Speculations are considered about synaptic efficacy and nerve connections in rat autonomic ganglia. It is suggested that six preganglionic fibers represent the mean input to a ganglion neuron.

Acetylcholine↗