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Muscle stretch-induced modulation of noxiously activated dorsal horn neurons of feline spinal cord
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Sports Medicine.ORCID iD: 0000-0001-7543-4397
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Sports Medicine.
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2004 (English)In: Neuroscience research, ISSN 0168-0102, E-ISSN 1872-8111, Vol. 48, no 2, 175-184 p.Article in journal (Refereed) Published
Abstract [en]

The present work was designed to check for the possibility of interactions between mechanical innocuous and chemically induced noxious muscle afferent inputs on discharge behavior of nociceptive superficial dorsal horn neurons (SDHNs) of the spinal cord in decerebrated cats. The innocuous and noxious stimuli were applied separately and in combination, so that the effects of the innocuous stimulus on nociceptive processing could be evaluated. The innocuous stimulus consisted of ramp-and-hold stretches of the gastrocnemius muscles, whereas the noxious stimulus consisted of i.a. injections of bradykinin (BK; 0.5-1 ml, 50 microg/ml) into the arterial circulation of same muscles. Only neurons up to approximately 1mm depth and those that responded to noxious pinch of the gastrocnemius muscles were selected for further analysis. The activity of 16 dorsal horn neurons was recorded extracellularly with high-impedance glass microelectrodes, out of which seven responded to stretch, while 12 neurons responded to bradykinin injections. The bradykinin injections induced three types of responses: excitatory, inhibitory and mixed. The majority of the neurons that showed excitatory and mixed responses to bradykinin were also influenced by stretches applied directly after the bradykinin injection. In these neurons, the stretch usually counteracted the bradykinin-induced response, i.e. shortening and reducing bradykinin-induced excitation and re-exciting the cells after bradykinin-induced inhibition. The mechanism of the stretch modulation is proposed to reside in a segmental spinal control of the nociceptive transmission.

Place, publisher, year, edition, pages
2004. Vol. 48, no 2, 175-184 p.
Keyword [en]
Action Potentials/drug effects/*physiology, Animals, Bradykinin/pharmacology, Cats, Muscle Contraction/drug effects/*physiology, Muscle Spindles/drug effects/*physiology, Muscle; Skeletal/drug effects/*physiology, Physical Stimulation/methods, Posterior Horn Cells/drug effects/*physiology, Stimulation; Chemical
National Category
URN: urn:nbn:se:umu:diva-16900DOI: 10.1016/j.neures.2003.10.009PubMedID: 14741392OAI: diva2:156573
Available from: 2007-10-18 Created: 2007-10-18 Last updated: 2016-02-26Bibliographically approved
In thesis
1. Effects of repetitive work on proprioception and of stretching on sensory mechanisms: implications for work-related neuromuscular disorders
Open this publication in new window or tab >>Effects of repetitive work on proprioception and of stretching on sensory mechanisms: implications for work-related neuromuscular disorders
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aims of the thesis were (i) to investigate the impact of repetitive low-intensity work exposure on proprioception and (ii) to examine effects of muscle stretching (especially sensory effects and effects on muscle nociception) and to relate its application to the prevention, alleviation and/or treatment of work-related neuromuscular disorders.

The effects of low-intensity repetitive work on the shoulder proprioception were tested in healthy subjects. The effect of working time on the retention of subjective fatigue and their relation to changes in proprioception, and the immediate effect of stretching on shoulder proprioception were investigated. A new method to test the stretchability of the rectus femoris muscle was investigated for reliability and validity and used to assess the effects of a two-week stretching regimen on range of motion and on subjective stretch sensation. Finally, the interactions between innocuous muscle stretch and nociceptive chemical stimulation on discharge behavior of nociceptive dorsal horn neurons in the feline spinal cord were explored.

The main findings were as follows: 1) The repetitive low-intensity work to fatigue diminished the shoulder proprioception; the working time as well as the retention of subjective fatigue were partly related to the extent of changed proprioception. 2) There was no effect of acute muscle stretching on the proprioception. 3) The new method for testing muscle stretchability proved valid and reliable. A two-week stretching regimen increased the tolerance to stretch torque, but the range of motion remained unchanged. 4) Half of the nociceptive dorsal horn neurons that responded to close arterial injections of bradykinin were modulated by muscle stretching applied directly after the injections.

Altogether, the results give credence to the hypothesis of an involvement of sensory information distortion due to repetitive low-intensity work exposure in the development of work-related neuromuscular disorders. Increased tolerance to stretch torque may be an important mechanism in explaining improvements following stretch treatment. The spinal interactions between innocuous stretch and nociceptive muscle afferent inputs indicate a possible mechanism involved in stretching-induced pain alleviation.

Place, publisher, year, edition, pages
Umeå: Kirurgisk och perioperativ vetenskap, 2004. 87 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 877
Medicine, Repetitive motions, Muscle fatigue, Proprioception, Muscle stretching, Work-related musculoskeletal disorders, Nociception, Ergonomics, Medicin
National Category
Dermatology and Venereal Diseases
Research subject
urn:nbn:se:umu:diva-211 (URN)91-7305-604-9 (ISBN)
Public defence
2004-03-19, Stora föreläsningssalen, Arbetslivsinstitutet, Umeå, 10:00 (English)
Available from: 2004-03-12 Created: 2004-03-12 Last updated: 2015-01-20Bibliographically approved

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