Splenocyte subsets in normal and protein malnourished mice after long-term exposure to cocaine or morphine

An experimental model which resembles human drug addiction was developed to study the effect of chronic drug (cocaine or morphine) administration on the immune system. As malnutrition has been associated with drug use, a low protein diet has been evaluated for its contribution to the impairment of the immune system during cocaine/morphine addiction. Female C57BL/6 mice that received a 20% or 4% casein diet were studied. Both drugs were administered intraperitoneally daily for 11 weeks and drugs were administered in increasing daily doses, beginning after 3 weeks of diet consumption. Doses of cocaine began with 5 mg/kg body weight and reached the maximum dose of 40 mg/kg/day at the fourth week. Doses of morphine gradually increased from 10 mg/kg to 75 mg/kg body weight with the maximum dose reached after 5 weeks of treatment. Cocaine administration reduced body weight, particularly in the low protein diet group, and spleen weight in protein malnourished mice. Cocaine as well as saline injected mice showed a decrease in the percentage of CD4⁺ CD8⁺ and Mac-1⁺ cells and an increase in B cells in the spleens of well nourished mice. Morphine-treated mice showed similar results to those observed in cocaine or saline treated mice. These results suggest that cocaine, morphine or saline injection can alter the percentage of cells that express a defined phenotype independently of the nutritional status of the subject. Moreover, the effect appears dependent on a stress mediated process.