MORPHINE TREATMENT IN-VITRO OR IN-VIVO DECREASES PHAGOCYTIC FUNCTIONSOF MURINE MACROPHAGES

Studies were performed to compare in vitro and in vivo effects of morp hine on the phagocytic function of murine peritoneal macrophages. Macr ophage monolayers were incubated with Candida albicans for 30 min in t he absence of autologous serum. Morphine added in vitro was found to d ecrease both the phagocytic activity (percent of phagocytic cells) and the phagocytic index (average number of ingested yeasts per cell) in a concentration-dependent manner, with maximal effects of 26% and 41%, respectively, at 10(-6) M. When morphine was administered in vivo via an implanted 75-mg pellet, there was a 22% decrease in phagocytic act ivity and a 40% decrease in the phagocytic index. Naltrexone completel y blocked the effects of morphine both in vitro and in vivo. The resul ts suggest that morphine is capable of interacting directly with opioi d receptors on macrophages, resulting in a decrease in phagocytic func tion.