The effect of opiates and opiate antagonists on heat latency response in the parasitic nematode Ascaris suum.
The effects of the opiates morphine and morphine-6-glucuronide (M6G), the mu opioid receptor specific antagonist D-Phe-Cys-Tyr-D-Trp-Om-Thr-Pen-Thr-NH(2) (CTOP), and the general opiate antagonist naloxone on the latency of response to thermal stimulation were determined in the parasitic nematode Ascaris suum. Thermal detection and avoidance behaviors of the worms were evaluated with a tail flick analgesia meter using a modification of a technique employed for nociception experiments in rodents. Morphine and M6G were shown to have a dose dependent analgesic effect on A. suum's latency of response to heat with morphine being the most potent. The analgesic effect of morphine was reversed by naloxone but not CTOP. Neither naloxone nor CTOP was able to block the analgesia of M6G. CTOP but not naloxone had significant analgesic effects on its own. These findings are generally consistent with previous results on the effects of opiates and nitric oxide release from A. suum tissue. Apparently these nematodes possess opioid receptors that effect nociception.
Pryor
Stephen C
SC
Neuroscience Research Institute, State University of New York at Old Westbury, Old Westbury, NY 11568, USA. pryors@oldwestbury.edu
Nieto
Fernando
F
Henry
Sherwyn
S
Sarfo
Jennifer
J
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D017165:Ascaris suum / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D015801:Helminth Proteins / Q000819:agonists*; D006358:Hot Temperature; D009292:Narcotic Antagonists / Q000494:pharmacology*; D010147:Pain Measurement; D017450:Receptors, Opioid, mu / Q000819:agonists*; D012377:Rodentia
D000701:Analgesics, Opioid; D015801:Helminth Proteins; D009292:Narcotic Antagonists; D017450:Receptors, Opioid, mu