Effect of morphine pretreatment on pentylenetetrazol-induced seizures in the rat.
In several species, larger doses of systemically-administered morphine induce seizures while smaller doses potentiate chemically-induced convulsions. However, it is generally considered that morphine acts as an anticonvulsant in the rat. In the present study, the effects of pretreatment with morphine on both electrical and motor manifestations of pentylenetetrazol (PTZ)-induced seizures in the rat were examined. Morphine (60 and 120 mg/kg) significantly delayed the onset of motor seizures induced by pentylenetetrazol but also induced a significantly greater number of motor seizures, a greater percentage of deaths and a lowering of the chemoconvulsive threshold for pentylenetetrazol. Recordings from animals with chronically-implanted supracortical electrodes showed that pretreatment with morphine (60 mg/kg) both altered the onset pattern of CNS excitation induced by pentylenetetrazol and delayed the onset of electrical seizure activity. These recorded electrocortical effects were similar to the behavioral effects observed in the non-implanted animals. Larger doses of morphine (175 and 250 mg/kg) by themselves produced both motor and electrocortical seizures in rats with chronically-implanted electrodes.
D000818:Animals; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004569:Electroencephalography; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D010433:Pentylenetetrazole / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012640:Seizures / Q000139:chemically induced* / Q000503:physiopathology
D009020:Morphine; D010433:Pentylenetetrazole