Interhippocampal Impulses: II. Apical Dendritic Activation of CAI Neurons

Abstract

A ndersen, P. Interhippocampal impulses. II. Apical dendritic activation of CAI neurons. C hakravarty, N. The occurrence of a lipid‐soluble smooth‐muscle stimulating principle (‘SRS’) in anaphylactic reaction. This work is an analysis of the commissural response of the field CAI of the hippocampus, a surface positive wave with a spike, followed by a negative wave. The major, later part of the surface positive wave was recorded negative in the layer of apical dendritic shafts. This deep negative wave is interpreted as a summated excitatory postsynaptic potential. It seems to have a causal relationship to the production of the spike. The spike most often showed its shortest latency in the apical dendritic shaft layer, increasing in both directions along the dendritic tree. The speed of propagation along the dendritic shaft was about 0.35 m/sec. The surface negative wave is confined to the basal layers and is probably partly due to the spread of the depolarizing wave along the dendrites and partly to the activity of alveus‐near located neurons. In the CAI apical dendritic membrane two mechanisms were found ‐ one was responsible for the production of the deep negative wave‐the other was responsible for the initiation and propagation of the spike along the dendrites.