Changes in the density of L-glutamate- and glycine-activated currents in spinal cord neuronal membranes during early embryogenesis

The pattern of change in the density of L-glutamate- and glycine-activated ionic currents through the spinal cord neuronal membrane of 6–11 day chick embryos was traced using an enzymatic technique for isolating cells during voltage-clamp experiments. A general trend towards increased current density was found during cell differentiation, followed by a substantial reduction in the density of glycine-activated current on the 9th day of incubation. A reciprocal relationship between densities of L-glutamate- and glycine-activated currents were characteristic of individual neurons. The functional significance of the patterns identified is discussed in connection with the evolution of spinal cord motor function during embryogenesis.