Differential effect of painful heterotopic stimulation on capsaicin-induced pain and allodynia.

Painful heterotopic stimulation (HTS) may inhibit experimental and clinical pain, an effect known as diffuse noxious inhibitory control (DNIC). This study examined the effect of painful HTS on capsaicin-induced pain intensity, brush-evoked pain intensity and area of brush-evoked pain in humans. Immersion of the foot into painful cold water significantly reduced capsaicin-induced pain intensity and brush-evoked pain intensity in the contralateral forearm, but did not change area of brush-evoked pain. The observed differential effect on the magnitude of pain and hyperalgesia on the one hand and area of hyperalgesia on the other suggests that the DNIC effect on spinal activity is selective and not general. Copyright 1998 Elsevier Science B.V.