An in vivo microanalytical technique for measuring the local biochemical milieu of human skeletal muscle

Abstract

Myofascial pain associated with myofascial trigger points (MTrPs) is a common cause of nonarticular musculoskeletal pain. Although the presence of MTrPs can be determined by soft tissue palpation, little is known about the mechanisms and biochemical milieu associated with persistent muscle pain. A microanalytical system was developed to measure the in vivo biochemical milieu of muscle in near real time at the subnanogram level of concentration. The system includes a microdialysis needle capable of continuously collecting extremely small samples (approximately 0.5 microl) of physiological saline after exposure to the internal tissue milieu across a 105-microm-thick semi-permeable membrane. This membrane is positioned 200 microm from the tip of the needle and permits solutes of <75 kDa to diffuse across it. Three subjects were selected from each of three groups (total 9 subjects): normal (no neck pain, no MTrP); latent (no neck pain, MTrP present); active (neck pain, MTrP present). The microdialysis needle was inserted in a standardized location in the upper trapezius muscle. Due to the extremely small sample size collected by the microdialysis system, an established microanalytical laboratory, employing immunoaffinity capillary electrophoresis and capillary electrochromatography, performed analysis of selected analytes. Concentrations of protons, bradykinin, calcitonin gene-related peptide, substance P, tumor necrosis factor-alpha, interleukin-1beta, serotonin, and norepinephrine were found to be significantly higher in the active group than either of the other two groups (P < 0.01). pH was significantly lower in the active group than the other two groups (P < 0.03). In conclusion, the described microanalytical technique enables continuous sampling of extremely small quantities of substances directly from soft tissue, with minimal system perturbation and without harmful effects on subjects. The measured levels of analytes can be used to distinguish clinically distinct groups.

Impact of nervous system hyperalgesia on pain, disability, and quality of life in patients with knee osteoarthritis: A controlled analysis

“…Another possible explanation of our findings is that lower PPT values over a spontaneously painful human skeletal muscle presents significantly elevated levels of substance P, calcitonin gene-related peptide, bradykinin, tumor necrosis factor ␣, interleukin-1␤, serotonin, and norepinephrine versus nonpainful, healthy subjects (31). The concentration of selected inflammatory mediators, neuropeptides, cytokines and catecholamines also differ quantitatively from a remote, uninvolved site (32).…”

Adverse events following trigger point dry needling: a prospective survey of chartered physiotherapists

“…[6][7][8] Eliciting LTRs can reduce concentrations of nociceptive chemicals, such as substance P and calcitonin gene-related peptide, found in the immediate vicinity of active TrPs. 9,10 Trigger point dry needling is commonly used in clinical practice by physiotherapists in conjunction with other physical therapy modalities. 1 In many countries, including Ireland, the United Kingdom, Canada, and Spain, TrP-DN has been recognized to fall within the scope of physiotherapy practice.…”

Muscle Pain and Muscle Spindles

“…Ischaemia, energy crisis and contraction metabolites increase the local concentration of inflammatory and pain metabolites leading to the development of painful trigger points. Shah et al [38] found significantly increased concentrations of [H + ], bradykinin, calcitonin gene-related peptide, substance P, tumour necrosis factor-α, interleukin-1β, serotonin and norepinephrine in active TrPs only. SEA in TrPs was stated to be different from spontaneous activity of normal neuromuscular junctions: the electrical discharges occur with frequencies that are 10-1000 times that of normal miniature end plate potentials [39].…”

“…The situation may be different in experimental studies, where the function of acetylcholinesterase was blocked [41]. The findings of microdialysis of trigger points [38] can be explained by intrafusal microdialysis: a twitch elicited by insertion of the capillary needle may show a myotatic reflex by the activation of intrafusal 1a-afferents of the given muscle spindle. Taut bands may be the final result of sustained reflex activation of beta motor units by intrafusal II-, III-and IV-afferents [25,27,28].…”