Kinetic characteristics of inhibitory postsynaptic currents in cultured chick embryo spinal cord neurons

Abstract

Decay of inhibitory postsynaptic currents (IPSC) was analyzed in dissociated culture of chick embryo spinal cord. Differences in the kinetic characteristics of low-amplitude and giant IPSC were revealed. Decay of currents in the first group was single-exponential, while decay in the second group was double-exponential. The time constant of single-exponential current decay increased during membrane depolarization and decreased during rise in temperature of the solution. Decay of the double-exponential currents depended little on potential, while temperature changes acted only on its slow component. Strychnine in submaximum concentrations produced not only a decrease in amplitude of giant IPSC, but also a deceleration of decay due to the slow component. The regularity of these phenomena suggests that decay of giant IPSC, as distinguished from that of low-amplitude currents, is determined by removal of transmitter from the synaptic cleft.