Journal of Neuroscience, Vol 7, 807-811, Copyright © 1987 by Society for Neuroscience
Voltage-dependence of glycine-activated Cl- channels: a potentiometer for inhibition?
DS Faber and H Korn
Single- and double-electrode voltage-clamp techniques have been employed in
situ to analyze Mauthner cell inhibitory synaptic responses produced both
by activation of the recurrent collateral network and by direct
intracellular stimulation of single presynaptic interneurons. The results
demonstrate that the synaptically evoked glycinergic postsynaptic currents
exhibit a striking voltage sensitivity. Specifically, the time constant of
the decay of the synaptic conductance is increased by depolarization and
decreased by hyperpolarization. This parameter is exponentially related to
membrane potential, changing e-fold for a 45 mV potential shift, regardless
of the degree of intracellular chloride loading or the magnitude of the
underlying synaptic conductance. In addition, the amplitude of this
inhibitory conductance change is decreased by membrane hyperpolarizations
of 15 mV or more. Computer modeling demonstrates that the voltage
dependence of the kinetics of the synaptic response may serve to enhance
the magnitude and duration of inhibitory responses appreciably in the face
of increased excitation.