thioinosine and Epilepsy

Nitrobenzylthioinosine (NBTI), a specific inhibitor of type 1 equilibrative nucleoside transporter, could regulate the extracellular adenosine concentration and have protective roles in seizures. However, the protection mechanism of NBTI in seizures remains poorly understood. Here, the expression pattern and subcellular distribution of adenosine A1 receptor were detected by Western blot analysis and double-labeling immunofluorescence staining in Lithium Chloride-Pilocarpine induced epileptic rat model. At 24 h after pilocarpine induced rat seizures, hippocampal slices were prepared and the evoked excitatory postsynaptic currents (eEPSCs) amplitude of pyramidal neurons in hippocampus CA1 region was recorded using whole-cell patch clamp. In vivo, compared to control group, Western blotting analysis showed that the expression of adenosine A1 receptor protein was increased at 24 h and 72 h after seizure, didn't change at 0 min and 1 w, and decreased at 2 w. Double-label immunofluorescence revealed that adenosine A1 receptor was mainly expressed in the membrane and cytoplasm of neurons. In Vitro, adenosine decreased the eEPSCs amplitude of pyramidal neurons in hippocampus CA1 region, NBTI also had the same effect. Meantime, NBTI could further inhibit eEPSCs amplitude on the basis of lower concentration adenosine (50µM), and adenosine A1 receptor inhibitor DPCPX partially reversed this effect. Taken together, we confirmed that the expression of adenosine A1 receptor protein was increased in the early seizures and decreased in the late seizures. At the same time, NBTI mimics adenosine to attenuate the epileptiform discharge through adenosine A1 receptor, which might provide a novel therapeutic approach toward the control of epilepsy.

Topics: Adenosine; Adenosine A1 Receptor Antagonists; Animals; Disease Models, Animal; Epilepsy; Gene Expression; Hippocampus; Male; Patch-Clamp Techniques; Protein Transport; Pyramidal Cells; Rats; Receptor, Adenosine A1; Thioinosine

The effects induced by adenosine and some related compounds upon Mg2+-free epileptogenesis were studied in slices of human epileptogenic neocortex maintained in vitro. Extracellular recordings revealed stimulus-induced and spontaneous epileptiform activity within 1-2 h of perfusion with Mg2+-free medium. A 30-90% decrease of the frequency of occurrence of spontaneous epileptiform discharges was induced by 40-50 microM adenosine while the analog 2-Cl-adenosine exerted a depressant effect (greater than 75% reduction in frequency of occurrence) at 0.3-3 microM. 2-Cl-adenosine also depressed stimulus-induced epileptiform responses and often blocked spontaneous epileptiform activity. Similar effects were seen during bath application of the adenosine uptake inhibitor nitrobenzylthioinosine (10-50 microM) indicating that endogenous adenosine can by itself influence epileptogenicity. Our data demonstrate that in the human epileptogenic neocortex a purinergic mechanism can control Mg2+-free epileptiform activity.

Topics: Adenosine; Cerebral Cortex; Epilepsy; Humans; In Vitro Techniques; Thioinosine