Anticonvulsant effect of morphine and morphine-like analgesics in Mongolian gerbils.

The effect of morphine, fentanyl, pethidine and pentazocine was studied in gerbils against air blast-induced seizures. Major, generalized seizures were suppressed by morphine (ED50 = 4.0 mg/kg s.c.), fentanyl (ED50 = 64 micrograms/kg s.c.), and pethidine (ED50 = 2.4 mg/kg s.c.), but not by pentazocine. The anticonvulsant effect of the drugs was lost with higher doses which partly induced spontaneous convulsions. The comparatively high potency of pethidine in this model may point to a role of other receptors (or processes) besides the mu-receptor for this drug.