Brief, prolonged and repeated stimuli applied to hyperalgesic skin areas: A psychophysical study

In this experimental study brief/prolonged and single/repeated, nociceptive stimuli (laser, thermode and electrical) were used to investigate sensory changes in capsaicin-induced primary and secondary hyperalgesia. The pain threshold to prolonged thermode stimulation was reduced in the primary area and remained constant in the secondary area. The pain thresholds to brief laser and electrical stimuli remained constant in the primary but reduced in the secondary area. The summation pain threshold to repeated (five stimuli delivered at 0.5, 1, 2 and 3 Hz) laser and electrical stimuli was reduced in the secondary area. The stimulus response functions to single laser and electrical stimuli were increased in the secondary area.