Modifications of NMDA-induced convulsive reactions in diazepam-tolerant rats

In acute experiments on rats, the mean ED₅₀ values of intraventricularly injected NMDA for evoking clonic seizures and tonic extension of the forelimbs were 0.69 and 11.36 μg per animal, respectively. When these indices were measured under conditions of the development of tolerance to diazepam (2 weeks from the abolition of a 3-week-long diazepam treatment, 0.5 mg/kg, i.p.), the dropped to 0.30 and 2.66 μg per animal, respectively. The results show that in diazepam-tolerant rats the sensitivity to the epileptogenic influence of NMDA increases, and such an increase is more significant with respect to tonic seizure manifestations. Neirofiziologiya/Neurophysiology, Vol. 32, No. 2, pp. 95–97, March–April, 2000.