Time-dependent effects of papaverine on electrically induced seizures in rats.

We tested the effects of papaverine, an adenosine uptake blocker, on hippocampal-elicited afterdischarges in rats. Rats were injected with 35 mg/kg papaverine and tested for seizure responses at 5, 20, and 60 min postinjection. Papaverine produced a potent inhibition of afterdischarge generation, greatly reduced afterdischarge duration, and blocked hippocampal-kindled seizures. This anticonvulsant effect was greatest 5 min postinjection and had largely dissipated by 60 min. Because papaverine also produced a Parkinson-like syndrome involving muscle rigidity, these results are discussed in terms of effects on dopamine and adenosine systems.