The effects of compound 48/80, morphine, and mast cell depletion on electroshock seizure in mice

The effects of compound 48/80 (C48/80), morphine, and mast cell depletion on maximal electroshock seizure (MES) were studied in Swiss albino mice.

An electrical current (60Hz, 0.2 msec) inducing convulsions in 50% of the animals (CC50) was assessed as 46 mA. Compound 48/80 (5 mg/kg) and morphine (100mg/kg) were administered subcutaneously. CC50 was applied separately to electroshock-unexposed animal groups at 15, 30, 60, 120, and 240 min after the onset of the experiment. In untreated controls, the percent of seizure induced by CC50 and percent of death among mice having convulsions were 50 and 20, respectively.

After C48/80, a significant increase in rates of seizure at 60th and 120th min and death beyond 60th min (p < .0001) indicates a pro-convulsive action of the drug, probably caused by a reduction in MES threshold. In contrast, rate of seizure tended to decrease following mast-cell depletion, which was readily reversed by C48/80 at the 60th min (p < .0001). Mast-cell depletion, alone or plus morphine, significantly increased the death percentage of convulsions. Morphine alone reduced the percentage of seizure induced by the application of CC50 in the mast-cell depleted animals (anticonvulsive action) but increased the percent of dying animals by as much as 100% at the 30th and 60th min (p < .0001). Combined morphine + C48/80 not only augmented the anticonvulsive effect of morphine at the 30th min but also nullified the rate of death among mice having convulsions.

We concluded that compound 48/80 (1) penetrates into the central nervous system to produce a central effect; (2) acts as pro-convulsive, and (3) paradoxically augments the anticonvulsive action of morphine, likely caused by the ability of the compound to increase the permeability of blood-brain barrier for morphine or by the release of histamine from mast cells in the brain, acting as anticonvulsant through the stimulation of H1 receptors or both. The precise mechanism of the increased death rate by C48/80 or morphine in intact and in mast-cell-depleted mice appears to involve pro-convulsive effects, cardiovascular impairment, and respiratory depression. The nullification of morphine-induced lethal toxicity by C48/80 could be due to the antagonistic interaction of the drug with opiate receptors in the brain.