Possible mechanism for the enhanced lethality of morphine in aggregated mice.

Morphine was shown to be more lethal to aggregated mice than to isolated mice at an ambient temperature of 29 degrees C but not at 19 degrees C. After morphine administration at 29 degrees C, convulsions were found to be associated with death, and a higher incidence of convulsions was observed in aggregated mice than in isolated mice. After morphine administration at 19 degrees C, there was no clear association between convulsions and death, and there was no significant difference between the incidence of convulsions in isolated and aggregated mice. When tactile stress was induced upon morphine-treated isolated mice at 29 degrees C, all of the mice convulsed and died. These results suggest that the greater lethality of morphine in aggregated mice is due to a greater incidence of convulsions which results from stress induced on one animal by the other.