Effect of Morphine on Leishmania Major Infection in BALB/C and C57BL/6 Mouse Strains

Morphine effect on reaction to some microbial infections by modulation of immune response. To evaluate the effect of acute morphine injection on Leishmania major infection in sensitive (BALB/c) and resistant (C57BL/6) mouse strains. In this experimental study, a low dose (2mg/kg) and a high dose (10mg/kg) of morphine in two doses were injected to two groups of each mouse, the first concordant with parasite inoculation and the second 15 days later (N=5 for each group). As controls, groups of mice received naloxone before injections of morphine and also a group of mice received saline. Local reaction at the site of parasite inoculation was measured once a week. Local reaction at the site of parasite inoculation increased till fifth week, then decreased and back to the normal size, In contrast, local reaction increased continuously and became multiple in control groups and mice which received low dose morphine. Local reaction did not increase substantially in mice which injected with 10mg/kg morphine so that there was a significantly difference between them and control group (P<0.05). The results of this study showed that acute morphine injection didn’t have a significant effect on the reaction to infection with Leishmania major of C57BL/6 mice, but had a biphasic dose-dependent effect on BALB/c mice reaction to infection with this parasite.