FIG. 1.

Neuropathic pain behavior after unilateral C5 spinal cord injury (SCI). (A) Rats with SCI showed a decreased paw withdrawal latency of the ipsilesional and contralesional forepaws in response to a noxious thermal stimulus that plateaued at 21 days post-injury (dpi) compared with baseline values (represented as a dotted line; p<0.01 vs. baseline values). (B) Similar decrease in paw withdrawal latency occurred in both the ipsilesional and contralesional hindpaws after SCI. (C) At 42 dpi, the thermal stimulus was perceived because all rats that responded produced supraspinal behaviors after any of the four paws were stimulated. (D) Before injury, rats withdraw their forepaws from a tactile stimulus of 60 g, while moderate unilateral C5 SCI causes a significant reduction in both ipsilesional and contralesional paw withdrawal thresholds in a subset of rats that is established by 14 dpi and persists over time. (E) Both the ipsilesional and contralesional hindpaw exhibited a similar response to tactile stimulation. (F) At 42 dpi, rats produced supraspinal behaviors in response to tactile stimulation of each paw, regardless of the presence or absence of allodynia. After SCI, the forepaws and hindpaws showed significantly greater incidence of supraspinal behaviors regardless of the presence or absence of allodynia compared with normal (*p<0.01). Dotted line denotes normal, baseline paw withdrawal latencies to noxious thermal stimuli (A,B) and baseline paw withdrawal thresholds to tactile stimuil (D, E). SEM=standard error of the mean.