Heterotopic pruritic conditioning and itch--analogous to DNIC in pain?
Pain can be endogenously modulated by heterotopic noxious conditioning stimulation (HNCS) through a mechanism which is known as diffuse noxious inhibitory control (DNIC). Since DNIC can be impaired in patients suffering from chronic pain, a comparable impaired itch inhibition may exist in patients suffering from chronic itch. The aim of the present study was to investigate whether heterotopic pruritic conditioning stimulation (HPCS) would display an impaired modulation of itch in patients suffering from chronic itch compared with healthy subjects. To this end, electrical stimuli were applied before and after histamine application (HPCS) to female patients with psoriasis and healthy female control subjects. Subjects reported the intensity of electrically evoked itch before and after HPCS. In order to replicate earlier findings for DNIC, electrically evoked pain was additionally investigated before and after cold stimulation (HNCS). As expected, the intensity of itch evoked by the electrical stimulus was significantly less after than before HPCS in healthy subjects, and the same was found for the intensity of electrically evoked pain after compared to before HNCS. Contrarily, in the patients levels of electrically evoked itch were significantly higher after than before HPCS, and no significant difference in pain intensity before and after HNCS was observed. In line with pain modulation, results suggest that there is a DNIC analogous mechanism for itch, i.e., diffuse pruritic inhibitory control (DPIC), which is impaired in patients with chronic itch, possibly due to a dysregulation of descending itch modulatory systems.
Department of Medical Psychology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands Pain and Nociception Neuroscience Research Group, Department of Anaesthesiology, Pain and Palliative Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands Department of Dermatology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Antoinette I M
AIM
van Laarhoven
Floris W
FW
Kraaimaat
Oliver H
OH
Wilder-Smith
Peter C M
PCM
van de Kerkhof
Andrea W M
AWM
Evers
D000328:Adult; D000368:Aged; D002490:Central Nervous System / Q000503:physiopathology; D002908:Chronic Disease; D003213:Conditioning, Psychological / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation / Q000009:adverse effects; D005260:Female; D006632:Histamine / Q000494:pharmacology; D017442:Histamine Agonists / Q000494:pharmacology; D006801:Humans; D008875:Middle Aged; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009434:Neural Pathways / Q000503:physiopathology; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D010146:Pain / Q000503:physiopathology; D011537:Pruritus / Q000139:chemically induced / Q000503:physiopathology*; D011565:Psoriasis / Q000503:physiopathology; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000502:physiology*; D012867:Skin / Q000294:innervation / Q000503:physiopathology*; D055815:Young Adult
D017442:Histamine Agonists; D006632:Histamine