Conductance changes during inhibitory postsynaptic potentials in normal and strychninized cortical neurons.

Abstract

Increases in ion conductance of up to 2-fold that of the neuron at the resting membrane level occurred during the early part of antidromi-cally induced inhibitory postsynaptic potentials (IPSP) in neurons of the motor cortex of barbiturate anesthetized cats. The conductance increase gradually declined during the subsiding phase of the IPSP, indicating a prolonged but gradually declining transmitter release or action. Conductance increases in some cells remained high after strychnine had depressed the voltage change associated with the IPSP; it seems possible that strychnine affects postsynaptic sites by altering an IPSP equilibrium level. Action potentials may occur as part of an anodal break response at the end of sufficiently strong rectangular polarizing currents. No evidence was obtained that this phenomenon occurs to a significant degree following the IPSP''s of motor cortex cells.