Suppression of Cerebellar Evoked Potentials by a peripheral action of diphenylhydantoin

Cerebellar evoked potentials were produced by muscle stretch, increased muscle tension and direct stimulation of axons originating in muscle nerves. Diphenylhydantoin, 10 mg/kg, suppressed only the cerebellar potentials evoked by muscle stretch indicating a suppression of muscle spindle function leading to a reduced cerebellar input. With larger DPH doses (total 60 mg/kg) cerebellar evoked responses produced by any of the above forms of stimulation were depressed indicating an impairment in the CNS. The data indicate that peripheral suppression of muscle spindles contributes to the cerebellar deficits observed in intoxication with diphenylhydantoin.