FACTORS INFLUENCING THE INCIDENCE OF REVERSIBLE LENS OPACITIES IN SOLITARY AND AGGREGATED MICE

¹ Department of Pharmacology, St. Mary's Hospital Medical School, London, England

After the injection of analgesic drugs, a much higher incidence of opacity was found in mice housed in groups or pairs than in those caged individually. The difference in effect was independent of body temperature and occurred in several strains of male and female mice. Although the incidence of lens opacity was greater in paired mice, the eyelids were not more widely retracted than in solitary mice. The lenticular action of methadone could be reduced in paired mice by placing them in large cages. Mice housed in pairs were much more active than solitary animals, the movement of one stimulating that of the other. Movement rates of mice which developed opacities were significantly higher than those which did not. Forced exercise of solitary housed mice restored the full lenticular effect of methadone. The phenomenon is discussed, and it is suggested that the lenticular action is potentiated in grouped mice by the raised blood lactate and pCO2 which results from the greater muscular activity.