STUDIES ON THE TRANSPORT OF MORPHINE INTO THE CEREBROSPINAL FLUID OF RABBITS

¹ Department of Pharmacology, University of Minnesota, Health Sciences Center Medical School, Minneapolis, Minnesota

The transport of morphine from the systemic circulation into the perfused cerebrospinal fluid was studied while the free morphine plasma concentration was kept constant with continuous infusion in rabbits whose renal vessels had been ligated. The transport of morphine into the cerebrospinal fluid from blood appeared to be a carrier-mediated process since morphine was transported against a concentration gradient and the transport was inhibited by compounds structurally related to morphine such as codeine, ethylmorphine, nalorphine and naloxone. Morphine transport was also inhibited by systemically administered organic basic compounds such as N-methylnicotinamide and SKF 525A and by dinitrophenol.