[Proconvulsant effect of morphine on seizures induced by pentylenetetrazol in the mice]

The present study was designed to investigate the proconvulsant effect of morphine (10, 30, 50 mg/kg, sc) in mice on pentylenetetrazol (PTZ)-, picrotoxin-, and bicuculline (BCC)-induced convulsions which are thought to be produced by interactions with GABAergic systems. Morphine increased the severity of seizures induced by the ip (50 mg/kg) and sc (90 mg/kg) routes of administration of PTZ. An administration of morphine caused an increased incidence of multiple seizures following both ip and sc administration of PTZ and prolonged the latency to onset of seizures induced by ip injection of PTZ. Repeated morphine administration (30, 50 mg/kg, ip x 4d) also caused an increased incidence of multiple seizures and the latency to onset of seizures by ip injection of PTZ. All these effects of morphine are naloxone-sensitive. Single morphine administration potentiated seizures induced by picrotoxin (2 mg/kg, iv) and BCC (20 mg/kg, iv). These results demonstrate that morphine has a proconvulsant effect on PTZ-induced seizures in the mouse.