PSYCHOTROPIC DKUGS 115 tency of pituitary glands; neither normal rabbit serum nor sheep heart antiserum had any effect. A pattern of vaginal cycling was observed after antihormone treatment which was not apparent in cycles of colntrols. No impolrtant differences were found in thymus weight or in adrenal or thyroid histology.

Hunter and Jasper(5) found that stimulation of intralaminar nuclei in the thalamus of the cat produced behavioral arrest, accompanied by a 3 per second spike and slow wave pattern in the EEG. Both behavioral and electrographic effects resembled those seen in petit ma1 epilepsy in man.Trimethadione is clinically effective in petit ma1 epilepsy ( 13). If this type of seizure originates in the intralaminar nuclei, trimethadione should depress this part of the brain. We have tested the effects of trimethadione on the intralaminar central lateral nucleus of the cat, as well as on the adjacent medial dorsal nucleus, cortex and hippocampus. The effects of trimethadione were compared with those of diphenylhydan toin and chlordiazepoxide (Libriuma) .Methods. Forty-one cats were prepared under ether anesthesia. The trachea was cannulated for artificial respiration and the left femoral vein for drug injection. Bipolar concentric electrodes were inserted with the aid of a stereotaxic instrument in central lateral or medial dorsal nuclei of thalamus, on frontal and parietal cortex (ectosylvian gyrus) , and in anterior and posterior hippocampus. All wound edges were infiltrated with procaine. The ether was withdrawn and the cat immobilized with decamethonium (C,,,) .Stimulation was with a Grass S-4 Stimulator. Parameters for medial dorsal nucleus, cortex and hippocampus were pulse duration 2 msec, frequency 40 per sec, duration of stimulation 5 sec, interval between stimulations 5 min. Initial intensity was 1 volt; this was increased by increments of 1 or 2 volts until an after-discharge appeared in the EEG, recorded on a Grass 111-C electroencephalograph. Current was monitored with a Tektronix 502 oscilloscope. Current a t threshold voltage was recorded as "threshold curat Harvard Libraries on June 29, 2015 ebm.sagepub.com Downloaded from

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