Behavioral interactions between opiate and antiepileptic drugs in the mouse.

Morphine and related opioid compounds are known to possess proconvulsant activity based upon both electroencephalographic and behavioral criteria. The present authors previously suggested that opiate-related seizures were behaviorally inhibitory, and this was further investigated in the present study. The effects of pretreatment with three pharmacologically distinct compounds (sodium valproic acid, trimethadione, taurine) upon normal behavioral activation to systemic morphine were examined in the mouse. Morphine consistently increased activity levels in comparison with vehicle. Each of the three experimental compounds itself was behaviorally inhibitory; nonetheless both sodium valproate and trimethadione facilitated behavioral responses to morphine. The effects of the same drugs upon activation produced by central administration of a long-lasting enkephalin analog (o-ala’-leu-enkephalinamide) were investigated, with similar results. These findings confirm a behavioral interaction between opiate and anticonvulsant drugs, although it may be selective for certain classes of anticonvulsant compounds.