Some antagonists of dantrolene sodium on the isolated diaphragm muscle of the rat.
The effects of a number of potential antagonists of dantrolene sodium have been studied on twitches of the isolated hemidiaphragm preparation of the rat stimulated directly at a frequency of 0-1 Hz, after complete neuromuscular block produced by tubocurarine or erabutoxin a. The substances selected as possible dantrolene antagonists were uranyl ions, thiocyanate ions, adrenaline, caffeine, quazodine, quinine, 4-aminopyridine and the calcium ionophore a23187, all of which facilitate excitation-contraction coupling in one way or another. Contracture was the main feature of the response to A23187, the increase in the tension of the dantrolene-depressed twitches being very slight. All the remaining compounds increased the amplitude of the twitches, but only 4-aminopyridine, quinine, quazodine and caffeine were capable of restoring to the control amplitude twitches that had been maximally depressed by dantrolene. OF these, 4-aminopyridine and quinine were the most potent on a molar basis.
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D003620:Dantrolene / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D003964:Diaphragm / Q000187:drug effects; D004558:Electric Stimulation; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D006827:Hydantoins / Q000037:antagonists & inhibitors*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D011725:Pyridines / Q000494:pharmacology; D011803:Quinine / Q000494:pharmacology; D051381:Rats; D013861:Thiocyanates / Q000494:pharmacology; D014501:Uranium / Q000494:pharmacology
D006827:Hydantoins; D011725:Pyridines; D013861:Thiocyanates; D000001:Calcimycin; D002110:Caffeine; D014501:Uranium; D011803:Quinine; D003620:Dantrolene; D004837:Epinephrine