The Journal of physiology
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The Journal of physiology · Jun 1976
Comparative StudyA comparison of the presynaptic and post-synaptic actions of pentobarbitone and phenobarbitone in the neuromuscular junction of the frog.
1. Pentobarbitone or phenobarbitone, in increasing concentrations up to 0-5 mM, progressively reduced the amplitude of miniature end-plate potentials (min.e.p.p.s). Pentobarbitone was the more potent of the two barbiturates in this regard. 2. ⋯ Therefore, over the range of concentrations examined the enhancement of transmitter release was quantitatively less than the reduction in responsiveness of the post-synaptic membrane. 4. Because of the greater ratio of post-synaptic to presynaptic actions, pentobarbitone was more potent than phenobarbitone in reducing synaptic efficacy (e.p.p. amplitude). 5. It is concluded that the presynaptic actions of pentobarbitone and phenobarbitone contribute significantly to barbiturate-induced changes in synaptic efficacy at low levels of transmitter release in the frog neuromuscular junction.