Quantitative Study of the Effects of Morphine on the Mouse Spleen and Inguinal Lymph Node

Background: Morphine, as a narcotic analgesic drug, can suppress the immune system including the spleen and lymph node during long-term administration. Quantitative studies can be an appropriate indicator for the assessment of organ dis- turbances. As such, this study aimed to determine the effect of chronic morphine treatment on the histological parameters of the spleen and lymph node, with the use of stereological methods. Methods: Nineteen male mice were divided into two groups, experimental and control. Addiction was induced by adminis- tration of 0.5% morphine solution in the experimental group. On day 71, after a physical dependency test, the animals were deeply anesthetized, dissected and their spleens and inguinal lymph nodes were removed. After histological preparation, the sections with a constant distance were selected and stained with hematoxilin-eosin. The total volume, red pulp, white pulp, and trabecular volume of the spleen as well as the total volume, cortex, nodule, medulla, medullary cord, and medul- lary sinus of the inguinal lymph node were calculated by Cavalieri’s and point-counting methods. Data were analyzed with the Mann-Whitney U test. Results: The mean total volume 34.87±6.74 mm³, mean white 9.57±2.66 mm³ and red pulp volume 24.10±4.65 mm³ of the spleen in the experimental group decreased significantly [~44% (P 0.001), ~43% (P 0.003), and ~39.5% (P 0.001), respectively]. The mean cortex 4.37±1.39 mm³ and nodule volume 1.67±0.70 mm³ of the inguinal lymph node in the ex- perimental group decreased significantly (P 0.04; ~31% and ~29.5%, respectively). In addition, the white blood cell count decreased in the experimental group 7.12±2.7 (~21%). Conclusions: Long-term use of morphine can suppress the immune system by reducing both the spleen and inguinal lymph node volume, and white blood cells.