Influence of adenosine, dipyridamole, adenosine antagonists and antiepileptic drugs on EEG after discharge following cortical stimulation.

The effects of adenosine (100 nM, icv), dipyridamole (DPM, 5 mg/kg, i.p.), adenosine A1 receptor antagonist 8-cyclopentyl-theophylline (8-CPT, 10 mg/kg, i.p.), and aminophylline (AMP) and caffeine (CAF) (at equivalent doses of 35 mg/kg, i.p.), were examined in rats. Anti-epileptic drugs (AEDs) were also administered i.p., viz, carbamazepine (CBZ, 10 mg/kg); phenobarbitone (PB, 10 mg/kg); phenytoin (PHT, 20 mg/kg); valproic acid (VPA, 300 mg/kg); and diazepam (DZP, 10 mg/kg), to study their effects on EEG after discharge (AD) and postictal depression (PID) induced by cortical stimulation. The AD parameters: (1) duration of EEG-AD (sec) and (2) number of spikes was noted both during pre and post drug treatment sessions. Adenosine and DPM had no special effects on AD parameters but showed significant prolongation of PID. All the adenosine antagonists, 8-CPT, AMP and CAF produced significant prolongation of AD duration, increase in number of spikes and reduced the duration of PID to a significant extent. Interestingly, some of the AEDs, viz. CBZ, VPA and DZP showed abolition of all the EEG-AD parameters whereas PB and PHT failed to show any significant effect. The results confirm previous findings on involvement of adenosine in postictal events.