Elsevier

Neuroscience Letters

Volume 221, Issues 2–3, 17 January 1997, Pages 157-160
Neuroscience Letters

The analgesic effects of R(+)-WIN 55,212–2 mesylate, a high affinity cannabinoid agonist, in a rat model of neuropathic pain

https://doi.org/10.1016/S0304-3940(96)13308-5Get rights and content

Abstract

The effects of a high affinity cannabinoid receptor agonist were evaluated in rats subjected to chronic constriction injury of the sciatic nerve (CCI) or a sham operation. Intraperitoneal (i.p.) injections of the active, but not the inactive enantiomer, alleviated the pain behavior exhibited by CCI animals in a dose dependent manner. Moreover, at doses ranging from 0.43 to 4.3 mg/kg effects on sensitivity to a heat stimulus were observed neither in the paw contralateral to the sciatic ligation, nor in animals subjected to sham surgery. Animals subjected to CCI and treated with 4.3 mg/kg exhibited hypoalgesia in the paw ipsilateral to the ligated sciatic, i.e. heat hypoalgesia was completely reversed. The hyporalgesia is presumed to be the results of unmasking of a sensory deficit reflecting the known loss of C and A delta with CCI. Although side effects were present in some CCI animals subjected to the high dose (4.3 mg/kg), a moderate dose (2.14 mg/kg) completely alleviated the thermal and mechanical hyperalgesia, and mechanical allodynia without side effects. In addition to identifying a potential drug treatment for painful neuropathy, this study suggests that changes in cannabinoid receptors occurs in nerve injured animals.

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