Antagonizing effect of morphine on the mobility and phagocytic activity of invertebrate immunocytes.

In the present study we have demonstrated that lipopolysaccharide (LPS) acts as an activator in the immunocytes of molluscs Planorbarius corneus, Mytilus edulis, and the insect Leucophaea maderae. This stimulatory effect, demonstrated by cellular conformational changes, is concentration- and time-dependent, and is antagonized by morphine. The inhibitory effect of morphine can be counteracted by naloxone. Morphine inhibitory action on immunocyte activity is also demonstrated by a decrease in the phagocytic activity. These data suggest that the downregulation of morphine is not limited to vertebrates but is also present in invertebrates.