Effects of McN‐A‐343 and DMPP on the uptake and release of 3H‐noradrenaline by guinea‐pig atria

Abstract

1 McN-A-343 4-(m-chlorophenylcarbamoyloxy)-2-butynyltrimethylammoniuin chloride and DMPP (N,N-dimethyl-N'-phenylpiperazinium iodide) inhibit the uptake of (±)-³H-noradrenaline by guinea-pig atria, being approximately as potent as cocaine in this respect. 2 The inhibition of uptake produced by McN-A-343 or DMPP was not affected by atropine or hexamethonium in concentrations which antagonized actions on muscarinic and nicotinic receptors respectively. 3 McN-A-343 in the presence of atropine had a positive inotropic action on atria, but this was not accompanied by efflux of radioactivity from atria previously incubated with (—)-³H-noradrenaline. 4 In the presence of McN-A-343, responses of atria to noradrenaline were increased and those to tyramine were decreased. 5 DMPP had positive inotropic and chronotropic actions on atria, and these effects were accompanied by an increase in efflux of radioactivity from atria previously incubated with (—)-³H-noradrenaline.