“After 60 min … the drugs, dextropropoxyphene , inhibited the cAP between 0.… and 0.5 mM, cocaine between 0.01 and 5 mM, codeine between 0.1 and 10 mM and morphine between 0.… and 70 mM. The inhibition caused by 5 mM morphine could not be reversed by naloxone.”