Effects of Naloxone Opiate Blockade on the Immunomodulation Induced by Exercise in Rats

Abstract The purpose of this study was to examine the possible involvement of the endogenous opiate system in the changes in immune competence induced by isolated exercise. Male untrained rats were subjected to a 2.5 hours swimming exercise bout. Animals were killed 15 min after the end of the exercise. The concentration of leukocytes, lymphocytes, monocytes and granulocytes and T4 (T-helper), T8 (T-suppressor/cytotoxic), interleukin-2 receptor (IL-2R) and transferrin receptor (TrfR) positive lymphocytes were determined both in peripheral blood and spleen by flow cytometric analysis. Exercise resulted in a significant decrease in 1) blood lymphocyte and splenic granulocyte number (p