Behavioural evidence for a bidirectional effect of systemic naloxone in a model of experimental neuropathy in the rat.

摘要: Abstract In animal models of inflammatory pain, we have demonstrated that the opioid antagonist naloxone induces a paradoxical analgesic effect at very low systemic doses, and hyperalgesic high doses. We therefore proposed, systems are modified in these animals with persistent pain. The aim present study was to investigate activity through another model pain rat due peripheral neuropathy sciatic nerve. created by 4 ligatures around analyzed effects i.v. (3 10 μg/kg, 1 mg/kg) on vocalization thresholds paw pressure 8 days after ligation. Three μg/kg produced significant antinociceptive responses from affected (with mean increase about 50 30% preinjection values, respectively) also non-affected paw, although less potent. By contrast, mg/kg elicited hyperalgesia paw. microdoses, but not those dose, were clearly related measured for each just before injection. This shows bidirectional neuropathic which contradicts current statement is opioid-resistant. results suggest processes, may be modifications