Pentylenetetrazol seizures in mice: effect on brain inosine and hypoxanthine.

Brain inosine and hypoxanthine were measured in mice at intervals following the intraperitoneal injection of pentylenetetrazol (PTZ), 100 mg/kg. These purines increased only after myoclonic jerks appeared and were maximal at the time of tonic hindlimb extension. Phenytoin and phenobarbital, which prevent tonic hindlimb extension, delayed the elevations of inosine and hypoxanthine. Although inosine has been found to have both epileptogenic and antiepileptic actions, the late increase in inosine found following PTZ probably has no physiological role.