Repeated low doses of morphine do not induce tolerance but increase the opioid antinociceptive effect in rats with a peripheral neuropathy.
In rats with a mononeuropathy, repeated low doses of morphine slightly enhanced its own effect in a paw pressure test of the lesioned limb. While the very effectiveness of morphine in neuropathic rats suggests that at least some nociceptive components of neuropathic pain might be sensitive to opioid receptor mechanisms, the absence of a rapid tolerance in this model indicates that tachyphylactic phenomena do not contribute to the reputed clinical ineffectiveness of opioids in neuropathic pain.
Neil
A
A
Unité de Recherche de Physiopharmacologie du Système Nerveux, U161, INSERM, Paris, France.
Kayser
V
V
Chen
Y L
YL
Guilbaud
G
G
D000700:Analgesics; D000818:Animals; D004361:Drug Tolerance; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009294:Narcotics / Q000494:pharmacology*; D009422:Nervous System Diseases / Q000503:physiopathology*; D010146:Pain / Q000503:physiopathology; D010525:Peripheral Nerves / Q000503:physiopathology*; D010812:Physical Stimulation; D051381:Rats; D011919:Rats, Inbred Strains; D012684:Sensory Thresholds / Q000187:drug effects
D000700:Analgesics; D009294:Narcotics; D009020:Morphine