Effect of H+ on the membrane potential of silent cells in the ventral and dorsal surface layers of the rat medulla in vitro.

Abstract

The effect of changing extracellular pH (pH e ) on the membrane potential of silent cells in brain slices taken from the ventral surface layer of the rat medulla oblongata was compared to the response of silent cells in dorsal slices. In both slices, about 50% of cells showed no significant alteration in their membrane potential when they were exposed to acid solution. However, in the ventral slice, 44% of cells were slowly depolarized by H+ without accompanying significant changes in membrane resistance. In the dorsal medulla, acid solution caused a slight and slow hyperpolarization of 34% of the cells, although a few were slightly depolarized. These silent cells were incapable of initiating action potentials and were assumed to be glial cells. After depression of the release of neurotransmitter(s) in the slice by reducing the [Ca2+] e and increasing the [Mg2+] e , silent cells were not depolarized by H+. A putative transmitter acetylcholine depolarized non-specifically the silent cell membrane.