Pentylenetetrazol seizure threshold in the rat during recovery phase from propofol and thiopentone induced anesthesia.

Pentylenetetrazol (PTZ) seizure threshold was determined in the rat during recovery from anesthesia induced by intravenous administration of propofol (20 mg/kg) or thiopentone (30 mg/kg). Seizure threshold values determined 10 min after the induction of anesthesia by either agents were significantly higher than those determined in control animals, indicating an anticonvulsant effect. With propofol, the initial rise in PTZ convulsive threshold declined rapidly during recovery from anesthesia and returned to control levels 40 min after drug administration. With thiopentone, the initial rise in convulsive threshold also declined during recovery phase but did not return to control levels at 90 min after drug administration. At no time during or after recovery from anesthesia induced by either anesthetic agents, did the PTZ conclusive threshold fall below control values. Thus, using the PTZ convulsive threshold, no proconvulsant effects were detected during the early phase of recovery from propofol or thiopentone induced anesthesia.