Nociceptive Assessment

Von Frey filaments (North Coast Medical, Morgan Hill, CA) were used for testing by applying pressure on hind paw ipsilateral to the surgical cuff and recording the response.24 Filaments were applied in ascending order through a mesh floor to the plantar surface. Responses included flinching, licking or biting of the paw, and hind paw withdrawal. The filament was applied 5 times, each application for ~3 s, with a 5 s interval separating each trial. The endpoint was three responses out of five trials. If less than 3 responses, the next higher filament value was used. If the filament on its own lifted the paw the next lower value was used. Allodynia was measured as a threshold response to withdrawal from stimulation applied to the hind paw on the same side as the implanted cuff. A threshold response that was lower than the responses on the un-operated side or in control animals demonstrated allodynia.