Within 2 hours, morphine injected into the third ventricle (ICV) in rats results in a decrease in blood but not spleen lymphocyte proliferation (Hernandez et al, 1993). To examine whether an immunosuppressive serum factor may be elaborated following morphine administration, serum (0.5 ml) from morphine-treated animals (20ug/5ul, ICV) or saline (5ul, ICV) was administered intravenously to naive animals. Serum from morphine-treated animals significantly suppressed blood responses. Serum from saline controls had no effect. To isolate a putative serum factor, morphine-treated donor serum was fractionated by molecular weight and added to blood or spleen cultures. Morphine serum filtrate with a molecular weight of ilOK suppressed blood responses, however, serum filtrate of si OK was without effect. The immunosuppressive effect of the serum was eliminated by boiling. These data suggest that morphine administration results in an immunosuppressive serum factor which may be protein in nature.
|Published - 1996