Quantitative study of the effects of morphine on the mouse spleen and inguinal lymph node

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 disturbances. 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.

Nineteen male mice were divided into two groups, experimental and control. Addiction was induced by administration 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 medullary sinus of the inguinal lymph node were calculated by Cavalieri's and point-counting methods. Data were analyzed with the Mann-Whitney U test.

The mean total volume 34.87+/-6.74 mm(3), mean white 9.57+/-2.66 mm(3) and red pulp volume 24.10+/-4.65 mm(3) of the spleen in the experimental group decreased significantly [approximately 44% (P<0.001), approximately 43% (P<0.003), and approximately 39.5% (P<0.001), respectively]. The mean cortex 4.37+/-1.39 mm(3) and nodule volume 1.67+/-0.70 mm(3) of the inguinal lymph node in the experimental group decreased significantly (P<0.04; approximately 31% and approximately 29.5%, respectively). In addition, the white blood cell count decreased in the experimental group 7.12+/-2.7 (approximately 21%).

Long-term use of morphine can suppress the immune system by reducing both the spleen and inguinal lymph node volume, and white blood cells.