Quantal components of the inhibitory synaptic potential in spinal mononeurones of the cat

1. Monosynaptic i.p.s.p.s were produced in spinal motoneurones of the cat by stimulation of a pool of interneurones following chronic degeneration of descending tracts and primary afferent fibres in the lumbosacral cord.2. Monosynaptic i.p.s.p.s so evoked by supramaximal stimuli often showed a fluct...

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Bibliographic Details
Published in:The Journal of physiology 1972-07, Vol.224 (2), p.287
Main Authors: Kuno, M, Weakly, J N
Format: Article
Language:English
Subjects:
Animals
Cats
Electric Stimulation
Electrophysiology
Evoked Potentials - drug effects
Factor Analysis, Statistical
Interneurons - physiology
Lumbosacral Region
Motor Neurons - drug effects
Motor Neurons - physiology
Nerve Degeneration
Neural Inhibition
Spinal Cord - physiology
Strychnine - pharmacology
Synapses - physiology
Synaptic Transmission
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Summary:1. Monosynaptic i.p.s.p.s were produced in spinal motoneurones of the cat by stimulation of a pool of interneurones following chronic degeneration of descending tracts and primary afferent fibres in the lumbosacral cord.2. Monosynaptic i.p.s.p.s so evoked by supramaximal stimuli often showed a fluctuation in amplitude with occasional failures of response.3. When two successive stimuli were applied at a short interval, the mean amplitude of the second i.p.s.p.s was greater than that of the first. This facilitation was associated with a decrease in the number of failures, a decrease in the coefficient of variation of the amplitude distribution and an increase in the probability of occurrences of large i.p.s.p.s.4. A statistical analysis of the i.p.s.p. amplitude fluctuation showed that the monosynaptic i.p.s.p. is composed of discrete unit potentials evoked with a certain probability in a manner described by a binomial law.5. The application of strychnine decreased the mean amplitude of i.p.s.p.s with little change in the coefficient of variation of the i.p.s.p. amplitude distribution.6. It is concluded that the release of inhibitory transmitter occurs in quantal steps and that strychnine blocks primarily the post-synaptic receptors for the inhibitory transmitter.
ISSN:0022-3751