Variations in electrophysiological properties of hippocampal neurons in different subfields.

Intracellular recordings were made from hippocampal pyramidal cells (HPCs) in subregions CA1a, b, c, CA2 and CA3a, b of the guinea pig hippocampal slice. There were significant differences in the mode of spike discharge at various sites. Most neurons in CA1b and CA3b fired single spikes spontaneously, or during intracellular depolarizing current pulses. HPCs in the CA1a and c, as well as CA2 and CA3a subregions usually had a burst mode of discharge under the same conditions. Basic differences in neuronal properties presumably underlie these varieties of behavior between or within various regions. Specification of the site or subregion of recording is important especially in those experiments where the mode of spike discharge or membrane events in HPCs are important variables.