Serotonin and serotoninergic agents affect proliferation of normal and transformed lymphoid cells.

Blastogenic transformation of murine spleen cells elicited with concanavalin A was suppressed by serotonin 10(-12) to 10(-6) M, and marginally stimulated by its antagonists ketanserin and propranolol in low concentrations (10(-15) to 10(-11) M). Ketanserin (5-HT2 receptor ligand) and propranolol (5-HT1A and beta-adrenergic ligand) did not block the suppressive effect of serotonin if used along with it in equimolar concentrations (10(-9) M). Ergot-alkaloid dihydroergosine suppressed, whereas dihydroergotoxin stimulated the blastogenic transformation. Opposite effects of the agents were obtained in experiments with mouse myeloma X63/Ag 8.653 and hybridoma SHV 125 cell lines, which unlike normal lymphoid cells, are homologous cell populations and proliferate spontaneously. The data indicate that serotonin and its antagonists interfere directly with mitosis and/or autocrine stimulation of target cells.