Naloxane enhanced inhibitory effect of verapamil on seizure induced by pentylenetetrazol in male rats

The role of opioid receptor and voltage dependent calcium channels on the kindling induced by the convulsant pentylenetetrazole (PTZ) were investigated in the rats. Experiment involved 24 rats which were divided into four groups. Kindling was established with PTZ in subconvulsive dose (37.5 mg/kg i.p.) every 48 h and effects were observed within 20 min using five-point scoring system. All animals were kindled to three consecutive-stage five seizures and their stability was tested. Saline, verapamil (calcium channel blocker), naloxone (opioid antagonist) or both of them were then administrated 20 min before PTZ application. Convulsant parameters were significantly (P<0.05) reduced by verapamil. Naloxone had no significant effect on the seizure expression of fully kindled animals, whereas simultaneous application of naloxone and verapamil had profound inhibitory effect on all seizure parameters. The results of the present study suggest that naloxane increased the inhibitory effect of verapamil on the seizure induced by PTZ kindling.