Effect of pentobarbital on thalamo- and hippocampocortical processes in rats

Experiments were carried out on 28 rats immobilized with d-tubocurarine. The effect of three successive doses of pentobarbital (PB--5, 15 and 40 mg.kg-1) on electrocorticographic manifestations (evoked responses, the rhythmic afterdischarge and barbiturate spindles, the self-sustained afterdischarge--SSAD) elicited by electrical stimulation of two thalamic nuclei with a different type of control projection and the hippocampus (CA3) was compared. We found no difference between the effect of PB on cortical electrographic manifestations elicited by stimulation of the dorsomedial part of the ventral nucleus (VDM) and the anterior lateral nucleus (LA) of the thalamus. Cortical responses elicited by stimulation of the hippocampus were heterogeneous and the effect of PB on them was smaller than on thalamocortical responses. Reduction of the hippocampocortical SSAD was likewise not significant until the deepest stage of barbiturate anaesthesia.