Pharmacological activation of spinal mGlu4 receptors does not modify mechanical sensitivity of naive rats but reduces mechanical hypersensitivity induced by inflammation or neuropathy. Time course of mean ± SEM of vocalization threshold to paw pressure (in grams) and area under the curve (AUC, g.min) of inflamed rats treated with vehicle, LSP4–2022 (as indicated in micrograms per rat, i.t.) or morphine (10 μg/rat, i.t.) administered on naive rats (A), on inflamed rats 240 min after carrageenan injection (B), and on mononeuropathic rats 2 weeks after ligature of the sciatic nerve (C) (n = 6–8 animals per group). *p < 0.05, vehicle versus treated conditions. **p < 0.01, vehicle versus treated conditions. ***p < 0.001, vehicle versus treated conditions.