Nonspecific convulsions are induced by morphine but not d-Ala²-methionine-enkephalinamide at cortical sites

Cortical application of morphine (25, 100 and 400 μg) induced cortical spikes in a dose-related fashion and, at 400 μg, behavioral and electrographic seizures. These electrographic seizures were not opiate specific since this activity occured undiminished in naltrexone-pretreated animals and was even potentiated in animals pretreated for 6 days with increasingly higher doses of systemic morphine. In contrast to the effects induced by morphine, the most consistent electrographic effect of cortically applied d-Ala²-methionine-enkephalin (DALA) and methadone was a depression of cortical EEG. These results support the hypothesis that the cortex and spinal cord together form the anatomical substrate of the documented nonspecific convulsive action of high systematically administered doses of morphine.