Effect of strychnine on evoked potentials and postsynaptic responses of sensomotor cortex neurons in the cat

In acute experiments on cats under light nembutal anaesthesia, immobilized by myorelaxants, superficial application of strychnine was shown to suppress the slow negative potentials (arising during direct and primary cortical responses) and IPSPs of the pyramidal neurons corresponding to the slow negative potentials. Iontophoretic application of strychnine blocks predominantly the early component of IPSP during which the input resistance is significantly less than that of the late component indicating their different genesis. It is concluded that individual components of evoked potentials have a common genesis, the slow negative potential is the reflection of the IPSP of pyramidal neurons whose early component seems to be generated by axo-somatic synapses while the late one by axo-dendritic inhibitory synapses. Neurotransmitters in these inhibitory synapses may be different.