ANTICONVULSANT ACTION OF ACUTE MORPHINE ADMINISTRATION IN RATS

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  • 1 January 1976
    • journal article
    • research article
    • Vol. 198  (3) , 655-660
Abstract
The effect of acute administration of morphine on cerebral excitability was investigated in rats with 2 convulsant drugs: flurothyl (hexafluorodiethyl ether) and pentylenetetrazol (PTZ). In the flurothyl study, adult male Sprague-Dawley (S-D) rats were injected s.c. with morphine sulfate in doses ranging from 0.5-256 mg/kg. At 15, 30, 60 and 120 min after morphine injection, flurothyl was administered by inhalation and the seizure thresholds were determined. In the PTZ study, 64 mg/kg of morphine sulfate were injected s.c. into both S-D and CFN (Wistar-derived) rats. Thresholds to PTZ seizures were measured after administering the convulsant either by the i.p. or i.v. route. An anticonvulsant action of morphine was shown on both flurothyl and PTZ. Peak time for this effect on flurothyl seizures was 30 min after s.c. administration of the opiate, with the maximal anticonvulsant activity appearing at the 64 mg/kg dose. The increase in seizure threshold in S-D rats at this dose was 36% with flurothyl, 94% with i.v. PTZ and 352% with i.p. PTZ. Morphine had a less dramatic influence on raising the latter seizure threshold in the CFN than in the S-D strain. The graded dose-related anticonvulsant action is independent of the respiratory depression associated with morphine adminstration and appears to be a reflection of an altered CNS excitability produced by the narcotic in rats.