ABSTRACT
Objective To develop experimental animal model of the brain stem myoclonus,which more closely replicate clinic features of mechanism, behavior, neuroelectrophysiology and pharmacodynamics.Methods L-5-HTP (the precursor of L-5-HT)was microinjected into the dorsal pons of young guinea pig to induce myoclonus (electromyogram burst of myoclonus≤400 ms by synchronous recording).Some animals were pretreated with anticonvulsant VPA,CZP or CBZ at effective dose 50 (EC_(50)).Myoclonus was induced when the drug level was within their effective anticonvulsion concentration.The neuroelectrophysiological characteristics of myoclonus including latency,time of reaching its peak,duration of seizure peak,the maximum seizure frequency and total duration were detected.EMG and ictal electroencephalogram(EEG)were recorded synchronously.The origin of myoclonus and its correlation with epileptic discharges were further confirmed by jerk-locked back averaging(JLA).Results (1)L-5-HTP induced pure myoclonus from the dorsal pons of guinea pig permanently(8/every site,the rate of producing myoclonus is 100%).(2)The myoclonus presented bilaterally or as general myoclonus,which was sensitive to tactile and sound sensation.(3)The EMG duration of the myoclonus wag longer((208.75 ± 81.42)ms),and ictal EEG showed scattered and irregular spikes and sharp waves without time-locked correlation with EMG activities.(4)The synchronous ictal EEG of the myoclonus showed spike and sharp waves,but there was no time-locked EEG activity in JLA.(5)In the animals treated with anticonvulsant at EC_(50) concentrations:VPA and CZP decreased the maximum seizure frequency(there are 28.13±3.79 per minutes in VPA group and 37.17±4.67 perminutes in CZP group)and shortened the duration of peak time ((55.00±14.14)minutes in VPA group and(50.00±11.73)minutes in CZP group respectively)and total time(VPA group was(124.17±40.04)minutes and CZP group was(156.88±30.71)minutes)of myoclonus(F value were between 23.41 and 35.44,P＜0.01 or P＜0.05).CBZ increased duration of peak time((98.75±13.86)minutes)and total time((257.50±14.79)minutes)of myoclonus(P＜0.05 and 0.01).Conclusions The new model generates pure myoclonus originating from brain stem and also has a shorter duration of muscle construction(≤400 ms)and more sensitivity to tactile and sound sensation.Therefore,the model presents characteristics closer to the brain stem myoclonus in the clinic phenotype in respect of seizure behavior,pharmacodynamics and neuroelectrophysiology.