Three-generation investigation on serotonin content in rat immune cells long after β-endorphin exposure in late pregnancy

Female rats were treated with P-endorphin on the 19th day of pregnancy. Serotonin content of immune cells (peritoneal lymphocytes, monocyte-macrophage-granulocyte group (mo-gran), mast cells, blood lymphocytes, granulocytes and monocytes, thymus lymphocytes) were studied in the mothers (P-generation four weeks after delivery), in the male offspring (171) generation (at seven weeks), in the female offspring (four weeks after their own delivery) and in their offspring (F-2 generation, at seven weeks). P-mother cells' serotonin content was not influenced by endorphin treatment, while F-1 generation's mo-gran and blood lymphocyte serotonin content was reduced (in contrast, histamine content of mo-gran increased). Four weeks after delivery, an increase in serotonin content was observed in the F-1 genera-tion in the peritoneal lymphocytes and mast cells as well as in blood lymphocytes. In contrast, serotonin content was reduced in blood granulocytes and monocytes. In the F-2 (grandson) generation, a reduction in mast cell serotonin content and sensitization of blood and thymic lymphocytes to repeated endorphin treatment was provoked. The significant changes were more expressed in the F-2 generation compared to F-1, also appearing earlier. The results unequivocally suggest that the increase in endorphin levels during late pregnancy can cause permanent changes in the F-1 and F-2 generations, which means that the imprinting effect can be transgenerationally transmitted.