The effect of the palmitoylethanolamide analogue, palmitoylallylamide (L‐29) on pain behaviour in rodent models of neuropathy

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Abstract
Background and Purpose: Cannabinoids are associated with analgesia in acute and chronic pain states. A spectrum of central cannabinoid (CB1) receptor‐mediated motor and psychotropic side effects limit their therapeutic potential. Here, we investigate the analgesic effect of the palmitoylethanolamide (PEA) analogue, palmitoylallylamide (L‐29), which via inhibition of fatty acid amide hydrolase (FAAH) may potentiate endocannabinoids thereby avoiding psychotropic side effects.Experimental Approach: Thein vivoanalysis of the effect of L‐29 on measures of pain behaviour in three rat models of neuropathic pain.Key Results: Systemically administered L‐29 (10 mg kg−1) reduced hypersensitivity to mechanical and thermal stimuli in the partial sciatic nerve injury (PSNI) model of neuropathic pain; and mechanical hypersensitivity in a model of antiretroviral (ddC)‐associated hypersensitivity and a model of varicella zoster virus (VZV)‐associated hypersensitivity. The effects of L‐29 were comparable to those of gabapentin (50 mg kg−1). The CB1receptor antagonist SR141716a (1 mg kg−1) and the CB2receptor antagonist SR144528 (1 mg kg−1) reduced the effect of L‐29 on hypersensitivity in the PSNI and ddC models, but not in the VZV model. The peroxisome proliferator‐activated receptor‐α antagonist, MK‐886 (1 mg kg−1), partially attenuated the effect of L‐29 on hypersensitivity in the PSNI model. L‐29 (10 mg kg−1) significantly attenuated thigmotactic behaviour in the open field arena without effect on locomotor activity.Conclusions and Implications: L‐29 produces analgesia in a range of neuropathic pain models. This presents L‐29 as a novel analgesic compound that may target the endogenous cannabinoid system while avoiding undesirable side effects associated with direct cannabinoid receptor activation.British Journal of Pharmacology(2007)151, 1117–1128; doi:10.1038/sj.bjp.0707326