Acetylcholine Sensitivity of Hippocampal Formation Neurons

Microiontophoretic application of acetylcholine to neurons in the CA1 pyramidal and dentate granule layers of the rabbit hippocampus revealed differences both in the number of cells excited and the nature of the excitation in the two populations of neurons. A smaller percentage (35.7%) of CA1 pyramidal neurons were found to be excited by acetylcholine, compared with the percentage (92.3%) of dentate granule cells excited. Excitation of CA1 pyramidal cells was slow in onset and antagonized by atropine. Excitation of dentate granule cells was rapid in onset and atropine did not specifically antagonize the action of acetylcholine on these cells.