[Comparison of 2 groups of neurons sensitive to the excitatory effect of acetylcholine in the cerebral cortex of the rat].

Two groups of neurons which are excited by the iontophoretic application of acetylcholine were described in the primary somatosensory cortex of the Rat. The first one is located in the middle part (group A) and the second one in the deepest part of the cortex (group B). Group A neurons had a higher average spontaneous activity than group B neurons. The latency of group A neurons responses to the iontophoretic application of acetylcholine was longer. The amount of iontophoretic current required to increase the discharge rate of the neuron by 200% was higher in group A than in group B. In contrast the average slope of the regression lines calculated from dose-response curves was not different between the two groups.