continuous cold water swim ( ccws , 3.5 min , 2 degrees c ) induces a non-opiate type of analgesia since 14 mg/kg of naltrexone or 20 mg/kg of naloxone only partially antagonize this stress-induced analgesia ( sia ) and since there is no cross-tolerance between ccws and morphine-analgesia .
C0027360
naltrexone
C0027358
naloxone