Table 1

Latency to observable movement following short-pulse (100 ms), high intensity stimulation with infrared diode laser (6.08 W/mm2)

Standing on 2 or 3 paws

Standing on 4 paws

Total

Total number of trials

8

8

16

Shortest latency to fLEM

56 ms

74 ms

56 ms

†Fastest conduction velocity

3.0 m/s

2.3 m/s

3.0 m/s

Mean latency to fLEM (± SEM)

159.5 ± 36.7 ms

250.0 ± 28.9 ms

204.8 ± 25.4

†Mean conduction velocity

1.1 m/s

0.7 m/s

0.8 m/s

Shortest latency to withdrawal of stimulated limb

74 ms

128 ms

74 ms

Mean latency to withdrawal of stimulated limb (± SEM)

213.0 ± 34.1

271.0 ± 27.7

242.0 ± 22.5

†Conduction velocities are likely a gross underestimation of the actual conduction velocities. They do not account for central delay (~80 ms in the rat) [32], motoneuron conduction velocity (33-85 m/s) [33] or the time required for muscle contraction/relaxation (34-116 ms) [33]. Nonetheless, we were able to demonstrate that it is possible to detect nocifensive behaviors that are temporally consistent with being mediated by Aδ-fibers. The posture of the animal before stimulation appears to greatly influence our ability to detect movements with short or longer latencies.

Mitchell et al. Molecular Pain 2010 6:94   doi:10.1186/1744-8069-6-94