The interaction of acetylcholine and d-tubocurarine on the end-plate free muscle membrane of rat diaphragm in low chloride solution.
The interaction of acetylcholine (ACh) and d-tubocurarine (dTC) on the membrane potential of end-plate free parts of rat diaphragm muscle fibres was studied using a conventional microelectrode technique. ACh only caused membrane depolarizations when the external chloride concentration was diminished. Therefore, all experiments were performed in a 40 mM Cl- containing medium. A bell-shaped log-dose response curve was obtained with ACh. Maximal depolarization occurred at 3.10(-4) M. The pD2 value for ACh was calculated to be 4.2. The log-dose response curve was shifted to the right in the presence of dTC; besides, the maximum seemed to be depressed. The pA2 values for dTC appeared to be 4.9. It was concluded from these data that the cholinergic receptors outside the end-plate region have binding properties, which differ considerably from those of end-plate or postdenervational receptors.
D000109:Acetylcholine / Q000494:pharmacology*; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002712:Chlorides / Q000502:physiology*; D003964:Diaphragm / Q000187:drug effects; D004347:Drug Interactions; D005260:Female; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D008566:Membranes / Q000187:drug effects; D009132:Muscles / Q000187:drug effects*; D009467:Neuromuscular Depolarizing Agents; D051381:Rats; D011950:Receptors, Cholinergic / Q000187:drug effects; D014403:Tubocurarine / Q000494:pharmacology*
D002712:Chlorides; D009467:Neuromuscular Depolarizing Agents; D011950:Receptors, Cholinergic; D000109:Acetylcholine; D014403:Tubocurarine