Spontaneous burrowing behaviour in the rat is reduced by peripheral nerve injury or inflammation associated pain.

Pain influences many aspects of daily living and effective analgesics should reinstate normal spontaneous daily behaviours. Experiments are described herein which show that the innate, spontaneous behaviour of burrowing by rats, which can be simply and objectively assessed by measuring the amount of gravel left in a hollow tube 1 h after presentation to the rat, is reduced by peripheral nerve injury (tibial nerve transection (TNT), L5 spinal nerve transection (SNT) and partial sciatic nerve ligation (PSNL)) and also following inflammation induced by intra-plantar injection of Complete Freund's Adjuvant (CFA). Gabapentin (100 mg/kg sc) but not at 30 mg/kg sc significantly reduced burrowing activity in naive rats. All peripheral nerve injuries and CFA reduced burrowing compared with shams and rats naive to surgery. The level of mechanical hypersensitivity in rats with peripheral nerve injury did not correlate with the deficit in burrowing indicating that different parameters of the holistic pain experience are measured in these paradigms. Gabapentin at 30 mg/kg sc, but not 100 mg/kg sc, reversed the deficit in burrowing induced by TNT and ibuprofen (30 mg/kg sc) reversed the effect of CFA on burrowing. These experiments show that measurement of burrowing is a simple, objective assay of innate rodent behaviour affected by pain that is ethologically relevant to the rat, does not rely wholly on evoking a reflex and can dissociate a selective analgesic dose of gabapentin from one inducing motor impairment in the same animal.

[The pharmacology of cannabinoid derivatives: are there applications to treatment of pain?]. / Pharmacologie des dérivés cannabinoïdes: applications au traitement de la douleur?

OBJECTIVE: To present the cannabinoid system together with recent findings on the pharmacology of these compounds in the treatment of pain. DATA SOURCES: Search through Medline database of articles published in French and English since 1966. Also use of other publications such as books on cannabis. STUDY SELECTION: All the relevant documents within the theme of this review were used. DATA EXTRACTION: All the data linked to the present topic were searched. DATA SYNTHESIS: Recent advances have dramatically increased our understanding of cannabinoid pharmacology. The psychoactive constituents of Cannabis sativa have been isolated, synthetic cannabinoids described and an endocannabinoid system identified, together with its component receptors and ligands. Strong laboratory evidence now underwrites anecdotal claims of cannabinoid analgesia in inflammatory and neuropathic pain. Sites of analgesic action have been identified in brain, spinal cord and the periphery, with the latter two presenting attractive targets for divorcing the analgesic and psychotrophic effects of cannabinoids. Clinical trials are now required, but are hindered by a paucity of cannabinoids of suitable bioavailability and therapeutic ratio. CONCLUSION: The cannabinoid system is a major target in the treatment of pain and its therapeutic potential should be assessed in the near future by the performance of new clinical trials.

Cannabinoids and pain.

Recent advances have dramatically increased our understanding of cannabinoid pharmacology: the psychoactive constituents of Cannabis sativa have been isolated, synthetic cannabinoids described and an endocannabinoid system identified, together with its component receptors, ligands and their biochemistry. Strong laboratory evidence now underwrites anecdotal claims of cannabinoid analgesia in inflammatory and neuropathic pain. Sites of analgesic action have been identified in brain, spinal cord and the periphery, with the latter two presenting attractive targets for divorcing the analgesic and psychotrophic effects of cannabinoids. Clinical trials are now required, but are hindered by a paucity of cannabinoids of suitable bioavailability and therapeutic ratio.