Experimental muscle pain produces central modulation of proprioceptive signals arising from jaw muscle spindles.
ABSTRACT The aim of the present study was to investigate the effects of intramuscular injection with hypertonic saline, a well-established experimental model for muscle pain, on central processing of proprioceptive input from jaw muscle spindle afferents. Fifty-seven cells were recorded from the medial edge of the subnucleus interpolaris (Vi) and the adjacent parvicellular reticular formation from 11 adult cats. These cells were characterized as central units receiving jaw muscle spindle input based on their responses to electrical stimulation of the masseter nerve, muscle palpation and jaw stretch. Forty-five cells, which were successfully tested with 5% hypertonic saline, were categorized as either dynamic-static (DS) (n=25) or static (S) (n=20) neurons based on their responses to different speeds and amplitudes of jaw movement. Seventy-six percent of the cells tested with an ipsilateral injection of hypertonic saline showed a significant modulation of mean firing rates (MFRs) during opening and/or holding phases. The most remarkable saline-induced change was a significant reduction of MFR during the hold phase in S units (100%, 18/18 modulated). Sixty-nine percent of the DS units (11/16 modulated) also showed significant changes in MFRs limited to the hold phase. However, in the DS neurons, the MFRs increased in seven units and decreased in four units. Finally, five DS neurons showed significant changes of MFRs during both opening and holding phases. Injections of isotonic saline into the ipsilateral masseter muscle had little effect, but hypertonic saline injections made into the contralateral masseter muscle produced similar results to ipsilateral injections with hypertonic saline. These results unequivocally demonstrate that intramuscular injection with an algesic substance, sufficient to produce muscle pain, produces significant changes in the proprioceptive properties of the jaw movement-related neurons. Potential mechanisms involved in saline-induced changes in the proprioceptive signals and functional implications of the changes are discussed.
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ABSTRACT: Osteoarthritis (OA) is a chronic disease, usually characterized by pain, which is associated with reduced muscle strength, disability and progressive loss of function. However, the pain influence over proprioception and motor behaviour remains unclear. Thus, the purpose of the study was to identify the levels of pain, the proprioceptive acuity and the pattern of muscle recruitment during stair ascent and descent in elderly patients with mild and moderate osteoarthritis (OA) compared to healthy subjects.BMC Musculoskeletal Disorders 09/2014; 15(1):321. · 1.90 Impact Factor
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ABSTRACT: Objectives: The aim of the study was to determine the effects of the chronic pain severity and pain duration in patients with osteoarthritis [OA] on pressure-pain threshold [PPT] and proprioception. Methods: The study groups consisted of patients with painful joints and healthy normal controls with painless joints. The chronic pain degree was evaluated with The Chronic Pain Grade Questionnaire. The PPT was measured with a dolorimeter and proprioception was evaluated passively. Results: Sixty-three patients with OA, mean aged 55 ± 10.60 years, were included in this study. Twenty-four patients had knee arthritis, eight patients had hip arthritis, and 31 patients had shoulder arthritis. The patients with OA had experienced pain for a duration of 41.09 ± 53.35 [12 to 72] months. The PPT was decreased and joint position sense and kinesthesia were altered in the painful joint when compared with the painless joint [P < 0.05]. No correlation was found between age, body mass index, pain duration, pain intensity score and PPT, joint position sense, or kinesthesia [P > 0.05]. However, the chronic pain grade was correlated with PPT [r = −0.418], joint position sense [r = 0.445], and kinesthesia [r = 0.535]. Similarly, correlations were found between disability points and PPT [r = −0.369], joint position sense [r = 0.473], and kinesthesia [r = 0.505]. Conclusions: Chronic pain grade correlates inversely with PPT, but it correlates directly with joint position sense, and kinesthesia senses in patients with OA. However, pain duration and pain intensity do not correlate with PPT, joint position sense, or kinesthesia.Journal of Musculoskeletal Pain 01/2010; 14(2). · 0.32 Impact Factor
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ABSTRACT: Shoulder injuries may be associated with proprioceptive deficits, however, it is unknown whether these changes are due to the experience of pain, tissue damage, or a combination of these. The aim of this study was to investigate the effect of experimentally-induced sub-acromial pain on proprioceptive variables. Sub-acromial pain was induced via hypertonic saline injection in 20 healthy participants. Passive joint replication (PJR) and threshold to detection of movement direction (TTDMD) were assessed with a Biodex System 3 Pro isokinetic dynamometer for baseline control, experimental pain and recovery control conditions with a starting position of 60° shoulder abduction. The target angle for PJR was 60° external rotation, starting from 40°. TTDMD was tested from a position of 20° external rotation. Repeated measures ANOVAs were used to determine differences between PJR absolute and variable errors and TTDMD for the control and experimental conditions. Pain was elicited with a median 7 on the Numeric Pain Rating Scale. TTDMD was significantly decreased for the experimental pain condition compared to baseline and recovery conditions (≈30%, P = 0.003). No significant differences were found for absolute (P = 0.152) and variable (P = 0.514) error for PJR. Movement sense was enhanced for the experimental sub-acromial pain condition, which may reflect protective effects of the central nervous system in response to the pain. Where decreased passive proprioception is observed in shoulders with injuries, these may be due to a combination of peripheral tissue injury and neural adaptations that differ from those due to acute pain.Manual Therapy 09/2014; 20(1). · 1.76 Impact Factor