Synaptic processes in pericruciate cortical neurons evoked by pyramidal tract stimulation in cats.
In cats anesthetized with chloralose and pentobarbital and immobilized with D-tubocurarine activity of 423 pericruciate cortical neurons was recorded (342 extra- and 81 intracellularly); 78 neurons had spontaneous activity. Stimulation of the pyramidal tract evoked antidromic action potentials in the pyramidal neurons with a latent period of 0.5-16.0 msec. Recurrent and lateral PSPs also developed both in pyramidal and in unidentified neurons in all layers of the cortex; IPSPs were recorded in 46.7% of neurons, EPSPs in 21.0%, mixed responses in 26.0%, and no visible changes were found in 6.3%. The latent period of the IPSPs was 1.5-14.0 msec, ther amplitude 1.3-17.0 mV, their rise time from 4 to 18 msec, and their duration 18-120 msec (sometimes up to 250-500 msec). In 30% of cases in which IPSPs appeared, their course was divided into two phases: fast (duration 10-20 msec) and slow. EPSPs developed after a latent period of 2.6-29.0 msec; their amplitude was 1.0-7.8 mV and their duration from 10.0 to 50.0 msec. In 51.2% of spontaneously active neurons the antidromic volley inhibited their activity in the course of 200-400 msec, in 19.5% it stimulated their activity, in 7.4% it had a mixed effect, and in 21.9% no visible change took place in their activity. The role and participation of axon collaterals of pyramidal neurons and of the interneuronal system in the formation of these processes are discussed.
D000818:Animals; D002415:Cats; D005071:Evoked Potentials; D007395:Interneurons / Q000502:physiology; D009044:Motor Cortex / Q000166:cytology / Q000502:physiology*; D011712:Pyramidal Tracts / Q000166:cytology / Q000502:physiology*; D011930:Reaction Time; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission