Background information: Chronic neuropathic pain induced in rats by ligation of the L5 and L6 spinal nerves has become one of the standard models for mechanistic studies of peripheral neuropathy and for the screening of novel analgesic compounds. Neuropathy is manifested by long-lasting referred pain (hypersensitivity to acute application of noxious (hyperalgesia) and non-noxious (allodynia) stimuli to the hind paw).

Animals: SD rats.

Efficacy test: The efficacy of systemic administered drugs can be evaluated after acute administration during the period of stable allodynia (approximately between days 9 and 28 after spinal nerves damage) (acute analgesic effect), or after repeated treatment in a preventive or curative protocol (disease-modifying effect, analgesia potentiation or tolerance). Efficacy evaluation of drug combinations is also possible, including isobolographic analysis of the interaction.

Assessments: Mechanical allodynia is evaluated by measuring hind paw withdrawal threshold (g) in response to mechanical (von Frey test) stimulation. Additional readouts could be evaluated (i.e., mechanical hyperalgesia) (not validated).

Positive control: Pregabalin (acute analgesic efficacy)

Criteria for significance: ANOVA followed by Tukey’s test is applied for comparison between the vehicle and treatment groups. Significant activity is considered at the P<0.05 level.

Turnaround time: xx Days.