Dependence of intrinsic plasticity on distal apical dendrites in rat dorsal hippocampal CA3 pyramidal neurons

Abstract

Intrinsic plasticity in the hippocampus plays a key role in the regulation of the hippocampal network. Previous works have identified that ventral CA3 pyramidal cells undergo enhancements in intrinsic excitability depending on the input that it receives, in particular, somatic stimulation at a physiologically relevant frequency of 10 and 20 Hz. However, it has not been identified whether this change in excitability is homogeneous throughout the hippocampal longitudinal axis. The dorsal and ventral structures of the hippocampus are involved in different forms of memory and behavior, and in turn, the dorsal and ventral CA3 also exhibit distinct characteristics. Therefore, the dorsal CA3 was examined for changes in intrinsic excitability. Here, I demonstrated two different preparation methods of the dorsal hippocampus, and that dorsal CA3 pyramidal cells also showed increased intrinsic excitability after a 10 and 20 Hz action potential train. Furthermore, I found that the morphology of CA3 pyramidal cells, specifically, the apical dendrite, plays a key role in inducing this change in intrinsic excitability. These results imply that the mechanism of long-term potentiation of intrinsic excitability is conserved along the longitudinal axis of the hippocampus.