Effect of opiate receptor blockade on pain sensitivity in the rat.
Blockade of opiate receptors by naloxone (2 mg/kg) was found to produce a significant increase in pain sensitivity as measured by the tail-flick test. This finding supports the view that endogenous opiate systems may play a role in the modulation of pain sensitivity. Naloxone, however, was found to have no effect on pain responsiveness as measured by tail-pinch. These findings, together with additional reports, suggest that endogenous opiate systems may exert differential actions on different sensory modalities.
D000818:Animals; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D010146:Pain; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*; D013623:Tail
D011957:Receptors, Opioid; D009270:Naloxone