Jx. Hao et al., Effects of intrathecal morphine, clonidine and baclofen on allodynia afterpartial sciatic nerve injury in the rat, ACT ANAE SC, 43(10), 1999, pp. 1027-1034
Citations number
53
Categorie Soggetti
Aneshtesia & Intensive Care","Medical Research Diagnosis & Treatment
Background: Increased response to mechanical or cold stimulation of hind pa
ws was observed in rats with partial sciatic nerve injury as a result of ph
otochemically induced ischemia. The present study examined the effects of i
ntrathecal morphine, clonidine and baclofen on the allodynia-like responses
.
Methods: The left sciatic nerves of rats were irradiated for 2 min with an
argon ion laser under chloral hydrate anesthesia. The threshold of paw with
drawal to mechanical stimulation was determined with a series of monofilame
nts (von Frey hairs). The response to cold stimulation was tested by sprayi
ng ethyl chloride on the plantar surface of the paw. When rats were exhibit
ing stable mechanical and cold allodynia-like behaviors after nerve injury,
the effects of i.t. morphine (1, 2, 7 mu g), clonidine (1, 2, 7 mu g) and
baclofen (0.1, 0.2, 0.7, 9 mu g) in a cumulative dose regime were investiga
ted.
Results: Intrathecal morphine dose-dependently alleviated the mechanical an
d cold allodynia without inducing motor impairment or sedation. Intrathecal
clonidine did not alter the response of kind paws to mechanical stimulatio
n, but reduced the cold allodynia. Intrathecal baclofen reduced the respons
es of rats to mechanical stimulation only at doses that also induced profou
nd motor deficits.
Conclusions: The present data suggest that intrathecal morphine, and to som
e extent clonidine, but not baclofen, alleviated the abnormal pain-related
behaviors in this new rat model of partial peripheral nerve injury. Differe
nces in the pharmacological profile between the present model and other mod
els of peripheral nerve injury are discussed.