Effects of substance P on neurones and glial cells in cultured rat spinal cord.

Substance P caused a depolarization of cultured spinal neurones which was often accompanied by a decrease in membrane conductance. The peptide usually had no effect on the membrane potential and resistance of glial cells. In contrast to the depolarization by glutamate, which is associated with an influx of Na+ and an efflux of K+, the action of substance P may be due to a decrease of the K+-conductance.