Mechanical Allodynia Assessment in a Murine Neuropathic Pain Model

Experimental animal models are unique tools (i) to study pain transmission and pathophysiology of neuropathic pain, (ii) to identify novel molecular targets and (iii) to test the potential analgesic effect of specific molecules. The chronic constriction injury (CCI) model of neuropathic pain is the first model of post-traumatic painful peripheral neuropathy, originally developed by Bennett and Xie in the late 1980s. The chronic constriction is performed in the sciatic nerve and induces a partial denervation involving myelinated afferent axons and unmyelinated axons. Damage to unmyelinated axons is much more severe than myelinated afferents. As the model induces a partial denervation, it is very useful for the analysis of pain behaviours. Stimulation of the hind paw, a target of the sciatic nerve, induces pain which can be quantitated. Thus, mechanical allodynia is usually assessed 7, 14 and 21 days after CCI of the sciatic nerve by measuring the hind paw withdrawal response to von Frey filament stimulation. Here, we describe in detail the protocol allowing a reliable and reproducible CCI model in mice. Overall, researchers most commonly use this surgical model to discover more efficacious drugs for the pharmacological control of chronic pain states.