EFFECT OF 4-AMINOPYRIDINE AND 3,4-DIAMINOPYRIDINE ON GUINEA-PIG ISOLATED ILEUM

1 4-Aminopyridine and 3,4-diaminopyridine produced concentration-depen dent contraction on guinea-pig isolated ileum incubated in Tyrode solu tion. The EC50 values were 1.14 x 10(-4) and 1.39 x 10(-4) M, respecti vely. 2 Calcium channel blockers such as verapamil, diltiazem, nifedip ine, flunarizine, and lanthanum chloride antagonized the contracting e ffect induced by 4-aminopyridine and 3,4-diaminopyridine in guinea-pig isolated ileum. 3 Diazoxide and atropine sulphate behaved similarly a s antagonists of the contracting effect induced by 4-aminopyridine and 3,4-diaminopyridine in guinea-pig isolated ileum. 4 It is concluded t hat the aminopyridines exert their effects through the release of acet ylcholine from parasympathetic nerve terminals.