TY - JOUR
T1 - Modulation of itch by conditioning itch and pain stimulation in healthy humans
AU - Andersen, Hjalte Holm
AU - van Laarhoven, Antoinette I. M.
AU - Elberling, Jesper
AU - Arendt-Nielsen, Lars
PY - 2017
Y1 - 2017
N2 - Little is known about endogenous descending control of itch. In chronic pain, descending pain inhibition is reduced as signified by lowered conditioned pain modulation (CPM). There are indications that patients with chronic itch may also exhibit reduced endogenous descending inhibition of itch and pain. This study aimed to investigate whether and the extent to which itch can be modulated by conditioning itch and pain stimuli. Twenty-six healthy volunteers participated. The study consisted of 5 conditions designed to systematically assess endogenous modulation of itch or pain: 1) itch-induced modulation of contralateral itch, 2) pain-induced modulation of contralateral itch, 3) pain-induced modulation of ipsilateral itch, 4) pain-induced modulation of contralateral pain, and 5) itch-induced modulation of contralateral pain. Conditioning stimuli were cold pressor-induced pain and histamine-evoked itch, while the test stimuli were electrical stimulation paradigms designed to evoke itch or pain. Pain was significantly reduced (CPM-effect) by the conditioning pain stimulus (p<0.001), but not by the conditioning itch stimulus (negative control condition). Itch was significantly reduced (CIM-effect) by both contra- and ipsilateral applied conditioning pain (both p<0.001), while conditioning itch stimulation only marginally reduced itch. Endogenous descending itch inhibition through mechanisms that are independent of segmental gating can be readily evoked by heterotopic conditioning pain stimulation. However, robust descending inhibition of itch cannot be evoked with itch conditioning stimulation.
AB - Little is known about endogenous descending control of itch. In chronic pain, descending pain inhibition is reduced as signified by lowered conditioned pain modulation (CPM). There are indications that patients with chronic itch may also exhibit reduced endogenous descending inhibition of itch and pain. This study aimed to investigate whether and the extent to which itch can be modulated by conditioning itch and pain stimuli. Twenty-six healthy volunteers participated. The study consisted of 5 conditions designed to systematically assess endogenous modulation of itch or pain: 1) itch-induced modulation of contralateral itch, 2) pain-induced modulation of contralateral itch, 3) pain-induced modulation of ipsilateral itch, 4) pain-induced modulation of contralateral pain, and 5) itch-induced modulation of contralateral pain. Conditioning stimuli were cold pressor-induced pain and histamine-evoked itch, while the test stimuli were electrical stimulation paradigms designed to evoke itch or pain. Pain was significantly reduced (CPM-effect) by the conditioning pain stimulus (p<0.001), but not by the conditioning itch stimulus (negative control condition). Itch was significantly reduced (CIM-effect) by both contra- and ipsilateral applied conditioning pain (both p<0.001), while conditioning itch stimulation only marginally reduced itch. Endogenous descending itch inhibition through mechanisms that are independent of segmental gating can be readily evoked by heterotopic conditioning pain stimulation. However, robust descending inhibition of itch cannot be evoked with itch conditioning stimulation.
KW - Itch
KW - pain
KW - conditioned pain modulation
KW - conditioned itch modulation
KW - descending inhibition
U2 - 10.1016/j.jpain.2017.07.002
DO - 10.1016/j.jpain.2017.07.002
M3 - Journal article
SN - 1526-5900
VL - 18
SP - 1437
EP - 1450
JO - Journal of Pain
JF - Journal of Pain
IS - 12
ER -