Effects of @entity2661 on the neuromuscular junction in the XXXX diaphragm.

@entity35 @entity1425 @entity5521 @entity3044 @entity2661 @entity1063 @entity43671 @entity934
1. The effects of @entity1063 , @entity1425 and @entity3044 on neuromuscular transmission in the @entity35 diaphragm and the influence of adrenergic blocking agents on these actions were investigated.2. The resting membrane potential of the muscle fibre was increased by @entity1425 (5 x 10(-6)-10(-5) g/ml.) and @entity3044 (5 x 10(-6) g/ml.) up to 3-4 mV, but @entity1063 (5 x 10(-6)-10(-5) g/ml.) had little effect.3. The amplitude and the half-decay time of the end-plate potential (e.p.p.) were increased by @entity1063 (1 x 10(-6) g/ml.), @entity1425 (1 x 10(-7)-10(-5) g/ml.) and @entity3044 (1-5 x 10(-6) g/ml.). The potentiation of the amplitude of the e.p.p. was greater with @entity1063 than with @entity1425 and @entity3044 .4. @entity1063 (5 x 10(-6) g/ml.) increased the frequency of miniature end-plate potentials (m.e.p.p.), but not their amplitude. However, @entity3044 (5 x 10(-6) g/ml.) increased the amplitude of m.e.p.p.s without change in frequency. @entity1425 (5 x 10(-6) g/ml.) increased both frequency and amplitude of m.e.p.p.s.5. @entity1425 (5 x 10(-6) g/ml.) and @entity3044 (5 x 10(-6) g/ml.) increased the input resistance of the muscle membrane. The effect was blocked by the beta-blocker, @entity43671 (2 x 10(-6) g/ml.), but not by the alpha-blocker, @entity5521 (2 x 10(-6) g/ml.). @entity1063 did not change the input resistance of the muscle fibre.6. @entity1063 (5 x 10(-6) g/ml.) and @entity1425 (5 x 10(-6) g/ml.) augmented the extracellularly recorded end-plate current (e.p.c.), but they had no effect on the half duration, nor on the action current (a.c.) of the nerve terminal, nor on the synaptic delay. @entity3044 (5 x 10(-6) g/ml.) had no effect on any of these parameters. The actions of @entity1063 and @entity1425 on e.p.c. were abolished by @entity5521 (2 x 10(-6) g/ml.), but not by @entity43671 (2 x 10(-6) g/ml.).7. @entity1425 (5 x 10(-6) g/ml.) and @entity3044 (5 x 10(-6) g/ml.) enhanced the amplitude of the @entity934 potential elicited by iontophoretic application of @entity934 . No such effect was produced by @entity1063 (5 x 10(-6) g/ml.).8. It was concluded that @entity1063 acts on the nerve ending increasing the release of transmitter, and that @entity3044 acts on the post-synaptic membrane enhancing the input resistance, while @entity1425 has both presynaptic and post-synaptic actions. The effect on the nerve ending is concerned with the alpha-action, whereas that on post-synaptic membrane with beta-action of the @entity2661 .
