The effect of tricyclic antidepressants on cholinergic responses of single cortical neurones.

1 The technique of microelectrophoresis was used in order to study the effects of tricyclic antidepressants on responses of single cortical neurones to acetylcholine. 2 Both potentiation and antagonism of excitatory responses to acetylcholine could be observed after a brief application of imipramine or desipramine. A higher dose of the antidepressant was required to evoke antagonism than to evoke potentiation. 3 Responses to carbachol were affected by desipramine similarly, suggesting the inhibition of cholinesterase is not responsible for the potentiation of cholinergic responses. 4 A brief application of atropine also had a dual effect on responses to acetylcholine. 5 It is suggested that the potentiation of excitatory cholinergic responses by atropine and the antidepressants may be due to the blockade of masked inhibitory receptors.