Modulatory effects of oligodendrocytes on the conduction velocity of velocity of action potentials along axons in the alveus of rat CA1 hippocampal region

Like neurons and astrocytes, oligodendrocytes have a variety of neurotransinitter receptors and ion channels. However, except fir facilitating the rapid conduction of action potentials by forming myclin and buffering cx1racellular K', little is known about the direct involvement of oligodendrocytes in neuronal activities. To investigate their physiological roles, we focused on oligodendrocyres in the alveus of the rat hippocampal CAi region. These cells were found to respond to exogenously applied glutamate bydepolarization through N-niethyl-D-aspartate (NMDA) receptors and non-NMDA receptors. Electrical stimulation of the border between the alveus and stratton oriens evoked inward currents through several routes involving gluta ilia tc receptors and inward rectifier K' channels. Moreover, electrical stimulation resembling in vivo activity evoked long-losting depolarization. To examine the modulatory cffccts of oligodendrocytes on neuronal activities, we petfornted dual, whole-cell recording on CAi pyramidal neurons and oligodendrocytes. Direct depolarization of oligodendi-ocytes shortened the latencies of action potentials evoked byantidroinicstimulation. These results indicate that oligodendrocytes increase the conduction velocity ofactionpotentials by a mechanisin additional to saltatory conduction, and that they have active roles in information processing in the brain.