Effect of digoxin, sodium valproate, their combination and celecoxib on neuroactive amino acids content and cerebral Na+, K+-ATPase activity in pentylenetetrazole-kindled mice

Our previous studies have shown moderate anticonvulsant efficiency of celecoxib as well as high efficiency of the combination of digoxin at subcardiotonic dose with widespread antiepileptic drugs at a sub- effective doses in various models of primary-generalized chemoinduced seizures. The aim of the study was to determine the efficiency of these medicines in the model of chronic epileptogenesis and the possible neurochemical mechanism of anticonvulsant action of digoxin and celecoxib per se as well as the combination of digoxin with sodium valproate. For this purpose, the effect on the course of pentylenetetrazole (PTZ) kindling, on the content of neurotransmitter amino acids (GABA, glycine, glutamate, aspartate) and the activity of Na+, K+-ATPase in the mice brain has been determined. PTZ kindling was chosen to its maximal pathogenetic similarity to human epilepsy. A total of 56 adult random-bred female albino mice weighing 20–24 g have been chosen. PTZ-induced kindling was simulated by the use of PTZ at a dose of 30 mg/kg intraperitoneally for 16 days. The classic antiepileptic drug sodium valproate has been used at a subeffective dose (1/2 ED50) of 150 mg/kg intra- gastrically. Digoxin was administered subcutaneously at a previously determined effective anticonvulsant dose of 0.8 mg/kg which is equal to 1/10 LD50. Animals of the combination group of digoxin and sodium valproate received drugs in the above-mentioned doses. Celecoxib as an anti-inflammatory agent capable of exhibiting anticonvulsant properties was administered at a dose of 4 mg/kg intragastrically. Sodium valproate and celecoxib were administered 30 minutes and digoxin – 15 min before PTZ administration. The content of GABA, aspartate, glutamate in the brain homogenate was determined by high-voltage electro- phoresis. Glycine content was determined by thin layer chromatography. Тhe activity of Na+, K+-ATPase was determined in the synaptosomal membranes. For 16 days, celecoxib did not affect the clinical course of kindling, when sodium valproate and digoxin per se showed moderate efficacy, and the combination of valproate + digoxin had a complete protective effect against spontaneous seizures. It has been found a statistically significant decrease in the content of GABA, glycine and increase in the content of glutamate, aspartate, as well as almost twofold decrease in Na+, K+-ATPase in the brains of untreated animals. All studied medicines (to a lesser extent – celecoxib, most pronounced – valproate + digoxin) contributed to the normalization of the balance of neurotrans- mitter amino acids. All drugs, except digoxin per se, significantly increased the activity of Na+, K+-ATPase (valproate + digoxin maximally). Therefore, the combination of sodium valproate with digoxin in terms of the effectiveness of seizure control and the influence on neurochemical mechanisms of neuronal excitability control significantly exceeded the effect of these drugs per se and celecoxib. The pronounced potentiation of the anticonvulsant activity of sodium valproate with digoxin determines the feasibility of further in-depth study of the mechanisms of action of this combination as a promising approach to the epilepsy treatment.