von Frey test.

To evaluate mechanical allodynia in mice, von Frey filaments with 5 different target forces (no. 1, 0.04 g; no. 2, 0.16 g; no. 3, 0.4 g; no. 4, 1 g; and no. 5, 2 g; Touch Test Sensory Evaluators; North Coast Medical) were used for mechanical stimulation to the plantar surface of the hind paw, as previously described (12, 13). Numbers of paw withdrawals from 5 stimulations per filament per mouse were counted. Mice were tested in randomized order at each time point.