naloxone and Schistosomiasis

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.

Topics: Analgesia; Animals; Body Temperature; Cricetinae; Kinetics; Male; Melatonin; Mesocricetus; Morphine; Naloxone; Pineal Gland; Receptors, Opioid; Schistosoma mansoni; Schistosomiasis; Time Factors