title: Mechanisms of depression of neuromuscular transmission by ATP and adenosine.
abstract: 1. The effects of ATP in the presence of theophylline and imidazole were investigated on the twitch tension of a partially magnesium blocked rat phrenic nerve-diaphragm preparation. Both theophylline and imidazole facilitate the neuromuscular transmission and prevent the effects of ATP. 2. The effects of adenosine in solutions with low calcium concentrations in the frog-sartorius and in solutions with very low calcium concentrations in the rat-diaphragm were studied on the miniature end-plate potentials. Adenosine caused a similar reduction of the frequency of the miniature end-plate potentials in both low and very low calcium concentrations. 3. The results are discussed in relation to the cyclic AMP and calcium hypothesis.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000241:Adenosine / Q000494:pharmacology / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D001001:Anura; D002118:Calcium / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D005260:Female; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009433:Neural Inhibition; D009469:Neuromuscular Junction / Q000502:physiology*; D051381:Rats; D009435:Synaptic Transmission / Q000187:drug effects; D013806:Theophylline / Q000494:pharmacology
chemical_list: D007093:Imidazoles; D000255:Adenosine Triphosphate; D013806:Theophylline; D000242:Cyclic AMP; D000241:Adenosine; D002118:Calcium