Size and duration of inhibition in the medial geniculate body in unanesthetized cats

A method which allows repeated micro-electrode recordings from subcortical structures without using any drugs is described. This method was adopted in combination with convential implantation techniques to study click-evoked potentials and inhibitory processes in the auditory system of the cat. The click-evoked potentials in MG were hardly affected by moderate doses of barbiturate and only to a minor degree in the auditory cortex. In the unanaesthetized animal the most significant contribution to the click-evoked inhibition in the auditory system was due to mechanisms in the MG. The inhibition was diminished both in size and duration as compared with the situation in anaesthetized cats. The MG cells showed a tendency to cyclic inhibition in the unanaesthetized cat, but not so regularly as following administration of sodium pentobarbital. The action of barbiturates on the auditory system is discussed.