title: Evidence for the activation of the endogenous opiate system in hamsters infected with human blood flukes, Schistosoma mansoni.
abstract: Nociceptive thresholds were investigated in golden hamsters infected with the human blood fluke, Schistosoma mansoni. Increases in thermal thresholds suggestive of analgesia were evident by 20-25 days of infection. These increased further during a 40-42 day period. The altered responses were suppressed by the opioid antagonist naloxone. Non-invasive inhibition of the activity of the pineal gland by exposure to light also reduced nocturnal analgesia in schistosome infected animals. Naloxone antagonism and pineal inhibition of morphine- induced analgesia was obtained similarly in control, uninfected animals. Taken together, these findings suggest strongly that infection with S. mansoni results in a chronic activation of the endogenous opiate system.
mesh_terms: D000698:Analgesia; D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D006224:Cricetinae; D007700:Kinetics; D008297:Male; D008550:Melatonin / Q000378:metabolism; D008647:Mesocricetus; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D010870:Pineal Gland / Q000502:physiology / Q000503:physiopathology; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*; D012550:Schistosoma mansoni; D012552:Schistosomiasis / Q000378:metabolism*; D013997:Time Factors
chemical_list: D011957:Receptors, Opioid; D009270:Naloxone; D009020:Morphine; D008550:Melatonin