[The cholinomimetic activity of alkyltrimethylammonium compounds in experiments on the isolated mollusk neuron and on frog and chicken skeletal muscle].

As revealed by contractile reaction of frog and chick muscles and by changes in the membrane current of isolated molluscan neurone, cholinomimetic activity of alkyltrimethylammonium compounds (ATMC) in the highest in drugs with 4 and 5 methylene groups in a molecule. The decrease in the activity with the decrease in the number of methylene groups was more evident in chick muscle; the decrease in the activity due to the increase in the number of these groups was most significant in experiments on molluscan neurone. Analysis of membrane current fluctuations showed that elementary current does not depend, whereas channel open time only slightly depends on the number of methylene groups in ATMC. However, with the increase of the number of methylene groups above 4, gradual decrease was observed in the ability of ATMC to increase at low (threshold) concentrations the membrane current (response) in the neurone. This decrease in the potency of ATMC correlated with the increase in Q10 value for neuronal response and calculated Q10 value for the reaction rate of ATMC with cholinoreceptor. The decrease in the activity of these ATMC is presumably due to a longer duration of complex formation with cholinoreceptor because of the higher energy barrier. ATMC with 8 and 9 methylene groups at high (saturating) concentrations elicited significantly smaller neuronal response with higher Q10 value. It is suggested that this phenomenon is due to a longer duration of complex formation with cholinoreceptor because of a higher energy cost.