Ouabain-sensitive and insensitive acetylcholine receptors on the membrane of the same neuron in Helix pomatia.
Using internally dialyzed neurons of Helix pomatia as a model, the effect of structural analogs of acetylcholine (ACh) were investigated for their cholinomimetic properties on A- and B-types of ACh-responses. Specifically we analyzed choline esters of N-para- and ortho-alkoxybenzoyl-beta-alanines, (CH(3)O-, C(2)H(5)O-, C(3)H(7)O-, iso-C(3)H(7)O-, C(4)H(9)O-, iso-C(4)H(9)O-, C(5)H(11)O-, iso-C(5)H(11)O-), (in all, 16 combinations). The compounds evoked differing sensitivities of response to factors de-activating the Na-K-pump (ouabain and K-free solution). Most compounds resembled ACh: ionic currents caused by these compounds were inhibited by Na-K pump blockers in the case of A-type responses - B-type responses were insensitive to these factors. Ionic currents induced by choline esters of p-, o-propoxy- and iso-propoxybenzoyl-beta-alanines were insensitive to ouabain and K-free solution in the case of A- and B-type responses. Ionic currents induced by the choline ester of p-butoxybenzoyl-beta-alanine were inhibited by ouabain and K-free solution on both types of neuron. The results allow us to classify choline esters of p-, o-propoxy- and iso-propoxybenzoyl-beta-alanines as N-cholinomimetics, while the choline ester of p-butoxybenzoyl-beta-alanine can be considered as M-cholinomimetic. We conclude that both M- and N-type ACh receptors exist on the membrane of the same neurons.
Grigorian
K P
KP
Institute of Fine Organic Chemistry, National Academy of Sciences, Yerevan, Armenia.
Azatyan
K V
KV
Kazaryan
S H
SH
Ayrapetyan
S N
SN
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D006372:Helix, Snails; D017136:Ion Transport; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology*; D011950:Receptors, Cholinergic / Q000187:drug effects* / Q000378:metabolism
D011950:Receptors, Cholinergic; D010042:Ouabain