Abstract

The actions of two cyclohexamine derivatives (1-(phenylcyclohexyl) piperidine monohydrochloride, Sernyl, Cl-395; and n-ethyl-1-phenyl cyclohexylamine monohydrochloride, Cl-400, cyclohexamine) have been tested in cats, using chronic preparations with implanted electrodes, and in acute experiments with local analgesia after surgical preparations under ether. Attention has been directed to effects of these drugs on a previously learned performance, and to their effects on correlated EEG records from the hippocampal system during the learned performance.

Intraperitoneal administration of either drug in doses of 1-3 mg/kg was found to suppress or seriously interfere with a learned approach in a T-maze situation for 8 to 24 hours.

Control EEG records from hippocampal structures in chronic animals exhibited a characteristic 6 cycles/second discharge during the approach performance, in agreement with our previous studies. This rhythmic discharge was abolished $$Word$$ the drugs within a few minutes of drug administration, and was accompanied by a failure in the animal's goal-directed behavior. The rhythmic discharge reappeared concurrently with return of the approach behavior during recovery from the drug. Our findings here lend weight to previous observations that this activity is a sensitive measure of the cat's capacity to perform goal-directed motor activity.

For 8 to 16 hours after drug dosage, a great deal of seizure spiking was observed in the records from the hippocampal system, and was frequently maximal in the entorhinal (pyriform) cortex. Seizure discharges in amygdaloid records were infrequent by comparison with those in hippocampal records.

In acute experiments, evidence was found of $$Word$$ with normal relations between the hippocampus and subcortical centers at both diencephalic and rostral midbrain levels. After drug dosage, stimulation of thalamic nucleus ventralis anterior consistently failed to elicit a hippocampal theta rhythm, and drug-induced changes in reticulo-cortical systems were seen.

The significance of temporal lobe structures, and the hippocampal system in particular, is discussed in relation to the laying down of normal memory traces of current performance.