Differential effects of phenobarbital, pentobarbital, and diphenylhydantoin on motor cortical and reticular thresholds in the rhesus monkey. Psychopharmacologia 2

In 1931, K~LL ~ and FCLTON described the action of various drugs on the motor cortex of monkeys. These authors concluded that pento-barbital sodium, in doses which produced light anesthesia, had little effect upon the motor cortex, whereas phenobarbital sodium, administered in equipotent anesthe~c doses, abolished motor cortical responses. Sub-sequently, M]m~I~T and PUT~A ~ (1938) found that phenobarbital markedly increased the convulsive threshold for electroshock in cats in non-anesthetic doses, while pentobarbital had little effect except in doses which produced profound drowsiness. Diphenylhydantoin was shown to possess greater anticonvulsant but less soporific effects than phenobarbital. The differential effecs of the two barbiturates upon cortical excitability and wakefulness, has been quoted as the basis for the usefulness of phenobarbital in the treatment of grand real epilepsy (GooI)~A ~ and GILMA ~ 1955). The present investigation was undertaken tore-evaluate he previous work of KELL ~ and FULTO ~ more quantitatively using techniques invohdng the response of monkeys with~chronically implanted electrodes to electrical stimulation of motor cortical and mesencephalic reticular si~es. ~lethods Five Maeaca mulatta monkeys, o ~ either sex, and weighing ~rom 2 to 4 kg had chronically indwelling stainless teel bipolar electrodes implanted in the mesencephalie r ticular formation and, subdurally, on the leg area of motor cortex. Four of these animals also had electrodes placed in the hippocampus. During surgery the animals were anesthetiz-ed with pentobarbital. Stereotaxie coordinates for implantation site