The Brennan model of post-operative pain consist on the incision of the hindpaw. Spontaneous pain can be monitored by measuring how the animal distributes the weight on each hindpaws, with a disbalance onto the contralateral paw. IP injection of the mGluR1 antagonist A-841720 compound produced an analgesic effect as the animal distributes equally his weight on each paw. Mechanical allodynia and thermal hyperalgesia are also proposed as read-out.