[Effect of pH on properties of the cholinoreceptive membrane of snail neurons].

The influence of pH on acetylcholine (ACh)-induced responses in completely isolated neurons of Lymnaea stagnalis was studied under voltage clapm conditions. The pH drop lead to a decrease in sensitivity of cholinoreceptive membrane; at pH 5.8-6.0 ACh-responses were eliminated completely. When raising the external pH (up to 10.6) there were no changes in the ACh effect. A group responsible for sensitivity changes of the cholinoreceptive membrane appears to have pK about 6.7. It is shown that the pH drop does not influence the ionic channel functional groups. The results can be explained in the assumption that some functionally important groups in the cholinoreceptor active site are protonated at low pH.