Experimental muscle pain impairs descending inhibition

Abstract

In chronic musculoskeletal pain conditions, the balance between supraspinal facilitation and inhibition of pain shifts towards an overall decrease in inhibition. Application of a tonic painful stimulus results in activation of diffuse noxious inhibitory controls (DNIC). The aims of the present experimental human study were (1) to compare DNIC, evoked separately, by hypertonic saline (6%)-induced muscle pain (tibialis anterior) or cold pressor pain; (2) to investigate DNIC evoked by concomitant experimental muscle pain and cold pressor pain, and (3) to analyze for gender differences. Ten males and 10 age matched females participated in two sessions. In the first session unilateral muscle pain or unilateral cold pressor pain were induced separately; in the second session unilateral muscle pain and unilateral cold pressor pain were induced concomitantly. Pressure pain thresholds (PPT) were measured around the knee joint before, during, and after DNIC induction. Cold pressor pain increased PPT in both males and females with greater increases in males. Hypertonic saline-evoked muscle pain significantly increased PPT in males but not in females. When cold pressor and muscle pain were applied concomitantly the PPT increases were smaller when compared to the individual sessions. This study showed for the first time that two concurrent conditioning tonic pain stimuli (muscle pain and cold pressor pain) cause less DNIC compared with either of the conditioning stimuli given alone; and males showed greater DNIC than females. This may explain why patients with chronic musculoskeletal pain have impaired DNIC.

Effects of an ethanol extract and the diterpene, xylopic acid, of Xylopia aethiopica fruits in murine models of musculoskeletal pain

“…The pain in the contralateral paws/limbs is therefore due to spinal and supraspinal neural changes with little or no primary afferent drive or input from the site of injury (ipsilateral limbs) once chronic pain has been developed (Coderre & Melzack 1985;Sluka et al 2001). XAE and XA may also have activated the descending inhibitory pain control system in the rostral ventral medulla (a group of nuclei with bilateral spinal projections and wide receptive fields covering the contralateral limbs) since the descending inhibitory control of pain is impaired in people with chronic musculoskeletal pain (Radhakrishnan et al 2003;Arendt-Nielsen et al 2008). The observation that XAE and XA also exert their analgesic effects partly by enhancing central mechanisms for mitigating pain also give credence to this suggestion (Woode et al 2013).…”

Prevalence of Myofascial Trigger Points in Fibromyalgia: The Overlap of Two Common Problems

“…As described previously, regional musculoskeletal pain often precedes the multiple regional pains in FM. It is evident that local muscle pain can induce dysfunction of descending pain inhibition [33]. Decreased descending pain inhibition also has been reported in patients with tension-type headache and migraine [34,35]; moreover, impaired descending pain inhibition can be normalized following surgical removal of peripheral noxious input in patients with painful hip osteoarthritis [36].…”

A Paradigm-Shift in Pain Medicine

“…Its ON-and OFF cells project downwards to the spinal dorsal horn, and facilitate or inhibit nociceptive input, respectively 30,31,141,148,149 . The PAG-RVM system is subject to a variety of supraspinal and cortical modulating inputs 148 , and has been demonstrated to control pain sensitivity in a variety of animal models for chronic pain states including arthritis, visceral and neuropathic pain 94,142,148,150 .…”