title: Conventional anticonvulsant drugs in the guinea-pig kindling model of partial seizures: effects of acute phenytoin.
abstract: This study addressed some of the controversial issues surrounding the anticonvulsant effect of phenytoin, and the predictive validity of the guinea-pig kindling model for the screening of anticonvulsant drugs. Following an intraperitoneal injection of either 50 or 75 mg/kg phenytoin, we analysed plasma concentrations of phenytoin at various time intervals. Behavioural toxicity was assessed at 0.5 h postinjection using quantitative locomotor tests, as well as scores on a sedation/muscle relaxation rating index. The anticonvulsant efficacy of phenytoin was evaluated from measurements of afterdischarge threshold (ADT), afterdischarge duration (ADD) and behavioural seizure severity at three phases of kindling: non-kindled, kindling acquisition (early and late) and kindled (50+ ADs). ADD and seizure severity were also measured in response to both threshold and suprathreshold kindling stimulation. Plasma levels of phenytoin corresponded to the human therapeutic range at the time of behavioural testing and kindling. Phenytoin did not exert significant adverse effects in guinea-pigs on both the behavioural tests and rating index. Phenytoin increased ADT in non-kindled and kindled guinea-pigs and effectively reduced ADD and seizure severity, indicating that the guinea-pig model correctly predicted phenytoin's anticonvulsant effect. Phenytoin produced reliable anticonvulsant activity in the guinea-pig at threshold stimulation but a somewhat reduced efficacy on seizure severity at suprathreshold stimulation intensities. Kindling in the guinea-pig is a valid model of human partial seizures.
authors.affiliation: Behavioural Neuroscience Research Group, Department of Psychology, University of Calgary, 2500 University Drive, NW, Calgary, Alberta, T2N 1N4, Canada.
authors.forename: T H
authors.initials: TH
authors.lastname: Gilbert
authors.forename: V
authors.initials: V
authors.lastname: Bharadia
authors.forename: G C
authors.initials: GC
authors.lastname: Teskey
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000927:Anticonvulsants / Q000097:blood / Q000378:metabolism* / Q000633:toxicity; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000187:drug effects* / Q000503:physiopathology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004558:Electric Stimulation / Q000009:adverse effects; D005260:Female; D006168:Guinea Pigs / Q000378:metabolism*; D007696:Kindling, Neurologic / Q000187:drug effects* / Q000502:physiology; D008297:Male; D010672:Phenytoin / Q000097:blood / Q000378:metabolism* / Q000633:toxicity; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D012640:Seizures / Q000188:drug therapy* / Q000503:physiopathology
chemical_list: D000927:Anticonvulsants; D010672:Phenytoin