Von Schwarzenfeld_1977_Br.J.Pharmacol_59_69

1 The pharmacological properties of N-2-hydroxyethyl-N-methyl pyrrolidinium (pyrrolcholine) and its acetate ester, recently shown to be a false transmitter at the cholinergic electromotor synapses in Torpedo marmorata, also those of the corresponding morpholinium compounds (morpholinecholine, acetylmorpholinecholine) have been studied on the guinea-pig ileum, frog heart, rectus abdominis muscle, rat blood pressure, rat gastrocnemius muscle and dorsal muscle of the leech. 2 Acetylpyrrolcholine and acetylmorpholinecholine are full cholinoceptor agonists with dose-response curves parallel to that of acetylcholine. They are, however, less potent. Acetylpyrrolcholine is relatively more potent as a muscarinic drug (molar potency about 30% of that of acetylcholine in the ileum but only 4% on the leech) whereas acetylmorpholinecholine is more strongly nicotinic. The unacetylated compounds are very weak agonists with potencies comparable to that of choline. 3 Pyrrolcholine in high concentration showed a distinct neuromuscular blocking effect in the rat gastrocnemius muscle preparation. It is likely that this is a direct effect and not due to uptake by the presynaptic nerve terminals followed by conversion to a false transmitter since it was not reduced by hemicholinium-3, which is known to block uptake of choline and choline analogues by the presynaptic high affinity choline uptake system.