Two‐component desensitization of nicotinic receptors induced by acetylcholine agonists in Lymnaea stagnalis neurones.

Publisher Website
Google Scholar
Abstract
The kinetics of desensitization induced by different agonists of acetylcholine (ACh) [tretramethylammonium bromide, caprylylcholine trimethylammonium, suberylcholine diiodide, sebacylcholine diiodide, ethoxysebacylcholine diiodide and succinylcholine diiodide]as well as the kinetics of recovery from desensitization, have been studied using the voltage-clamp technique in isolated, identified L. stagnalis neuron. Desensitization follows the sum of 2 exponentials: one fast and one slow. The time constant of the fast desensitization component under ACh application is in the range of seconds at room temperature (18.degree.-23.degree. C). It increases upon cooling Q10 = 2.8 .+-. 0.9, decreases with increasing ACh concentration and is independent of membrane voltage. The time constant of the slow component of desensitization is in the range of tens of seconds. It decreases with increasing drug concentration and is weakly dependent upon temperature (Q10 = 1.3 .+-. 0.4). The relative amplitude of the fast component, estimated by back extrapolation to the position of the peak current, increases with agonist concentration and decreases upon cooling. Recovery from desensitization follows the sum of 2 exponentials with time constants .**GRAPHIC**. and .**GRAPHIC**. of the order of seconds and minutes, respectively. Cooling prolongs the slow component (Q10 of .**GRAPHIC**. is .apprx. 3) and reduces its contribution during recovery. A comparison of the desensitization induced by various agonists indicates that for the small monoquaternary agonists the onset and recovery of desensitization resemble the onset and recovery observed with ACh. For more bulky agonists, like ethoxysebacylcholine, sebacylcholine and suberylcholine, the decay of the response during prolonged application of the agonist may involve an additional blocking process.

This publication has 28 references indexed in Scilit: