Effect of types and anatomical arrangement of painful stimuli on conditioned pain modulation.

The journal of pain : official journal of the American Pain Society

PubMedID: 25464158

Klyne DM, Schmid AB, Moseley LG, Sterling M, Hodges PW. Effect of types and anatomical arrangement of painful stimuli on conditioned pain modulation. J Pain. 2014;.
Reduced pain perception during painful stimulation to another body region (conditioned pain modulation [CPM]) is considered important for pain modulation and development of pain disorders. The various methods used to study CPM limit comparison of findings. We investigated the influence of key methodological variations on CPM, and the properties of CPM when the back is used for the test (TS) or conditioning (CS) stimulus. Two different TS (pressure pain threshold [PPT] and pain response to suprathreshold heat [Pain-45]) were assessed before and during application of a noxious or non-noxious (sham) CS. Eight blocks of trials varied the anatomical location (back and forearms) and arrangement (body side) of the stimuli. PPT (as the TS) increased during application of noxious, but not non-noxious CS when stimuli were applied to opposite body sides or heterotopic sites on one body side. Inconsistent with pain-induced CPM, Pain-45 decreased during both noxious and non-noxious CS. These findings indicate; (i) PPT can be more confidently interpreted with respect to CPM evoked by a painful stimulus than Pain-45, (ii) the back and forearm are equally effective as sites for stimuli; and (iii) stimuli arrangement does not influence CPM, except for identical anatomical regions on the same body side.PERSPECTIVE
This study indicates PPT as the TS provides a more valid measure of pain-induced CPM than pain response to a suprathreshold heat stimulus. Induction and magnitude of CPM is independent of stimuli arrangement, as long as ipsilateral homotopic sites are avoided. Findings clarify methods to study CPM.