[The reactions of the cortical neurons to the microiontophoretic delivery of acetylcholine to their dendrites].

In slices of parietal cortex of a guinea pig spike reactions were studied induced in neurons by iontophoretical applications of acetylcholine to their somata and dendrites. The results were obtained from 128 units. When applied to different sites of the neuronal membrane acetylcholine produced an increase in firing activity nearly in the same percent of cases (50-75%). The reactions to acetylcholine were most typical for spontaneously active neurons. The slow onset (to 8 sec) and long duration (to 25 sec) of responses evoked by acetylcholine point to an involvement of muscarinic receptors. Spike responses evoked by acetylcholine application to soma and dendrites were of the same latencies and magnitude. The most distant dendritic site where the acetylcholine excitation was able to evoke response of the soma was separated from it by 300-400 mcm. It is suggested that acetylcholine excitation propagates from dendritic points to the soma with intracellular biochemical processes.