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Functional changes in muscle afferent neurones in an osteoarthritis model: implications for impaired proprioceptive performance.

Wu Q, Henry JL - PLoS ONE (2012)

Bottom Line: Depolarizing intracellular current injection elicited more APs in models than in naïve muscle afferent neurones (P = 0.01) indicating greater excitability.The present study demonstrates changes in hind limb stance accompanied by changes in the functional properties of muscle afferent neurones in this derangement model of OA.This may provide a possible avenue to explore mechanisms underlying the impaired proprioceptive performance and perhaps other sensory disorders in people with OA.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada.

ABSTRACT

Background: Impaired proprioceptive performance is a significant clinical issue for many who suffer osteoarthritis (OA) and is a risk factor for falls and other liabilities. This study was designed to evaluate weight-bearing distribution in a rat model of OA and to determine whether changes also occur in muscle afferent neurones.

Methodology/principal findings: Intracellular recordings were made in functionally identified dorsal root ganglion neurones in acute electrophysiological experiments on the anaesthetized animal following measurements of hind limb weight bearing in the incapacitance test. OA rats but not naïve control rats stood with less weight on the ipsilateral hind leg (P = 0.02). In the acute electrophysiological experiments that followed weight bearing measurements, action potentials (AP) elicited by electrical stimulation of the dorsal roots differed in OA rats, including longer AP duration (P = 0.006), slower rise time (P = 0.001) and slower maximum rising rate (P = 0.03). Depolarizing intracellular current injection elicited more APs in models than in naïve muscle afferent neurones (P = 0.01) indicating greater excitability. Axonal conduction velocity in model animals was slower (P = 0.04).

Conclusions/significance: The present study demonstrates changes in hind limb stance accompanied by changes in the functional properties of muscle afferent neurones in this derangement model of OA. This may provide a possible avenue to explore mechanisms underlying the impaired proprioceptive performance and perhaps other sensory disorders in people with OA.

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Activation threshold of dorsal root in control and OA animals.A 0.04 ms rectangular pulse stimulus was delivered to dorsal roots at 4 weeks after surgery in control and in OA animals. (A) Shows the comparison of minimal electrical current sufficient to evoke an AP between OA (N = 25) and control muscle afferent neurones (N = 21). The Mann-Whitney U-test was used. (B) Shows the number of neurones evoked at various current strengths to the dorsal root in both control and OA muscle afferent neurones.
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pone-0036854-g004: Activation threshold of dorsal root in control and OA animals.A 0.04 ms rectangular pulse stimulus was delivered to dorsal roots at 4 weeks after surgery in control and in OA animals. (A) Shows the comparison of minimal electrical current sufficient to evoke an AP between OA (N = 25) and control muscle afferent neurones (N = 21). The Mann-Whitney U-test was used. (B) Shows the number of neurones evoked at various current strengths to the dorsal root in both control and OA muscle afferent neurones.

Mentions: To determine the activation threshold of the dorsal root rectangular pulse stimuli were delivered at a current strength just sufficient to evoke an AP. This minimum activating current delivered from the dorsal root in control animals was 0.35±0.12 mA (N = 21), and was not different from that in OA animals, in which this value was 0.17±0.11 mA (N = 35; Mann-Whitney U-test, P = 0.1; Figure 4A). In control neurones, the percentage of neurones activated at various current strengths was shown as follows: 0.1 mA (23.8%), 0.2 mA (47.6%), 0.3 mA (14.3%), 0.5 mA (4.8%) and >0.5 mA (9.5%) There was also no difference in the composition of the number of neurones activated at different current strengths between control and OA animals (Chi-square test, P = 0.29; Figure 4B); in OA animals, the composition was: 0.1 mA (40%), 0.2 mA (52%), 0.3 mA (8%), and none for the 0.5 mA and >0.5 mA current strengths.


Functional changes in muscle afferent neurones in an osteoarthritis model: implications for impaired proprioceptive performance.

Wu Q, Henry JL - PLoS ONE (2012)

Activation threshold of dorsal root in control and OA animals.A 0.04 ms rectangular pulse stimulus was delivered to dorsal roots at 4 weeks after surgery in control and in OA animals. (A) Shows the comparison of minimal electrical current sufficient to evoke an AP between OA (N = 25) and control muscle afferent neurones (N = 21). The Mann-Whitney U-test was used. (B) Shows the number of neurones evoked at various current strengths to the dorsal root in both control and OA muscle afferent neurones.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3351471&req=5

pone-0036854-g004: Activation threshold of dorsal root in control and OA animals.A 0.04 ms rectangular pulse stimulus was delivered to dorsal roots at 4 weeks after surgery in control and in OA animals. (A) Shows the comparison of minimal electrical current sufficient to evoke an AP between OA (N = 25) and control muscle afferent neurones (N = 21). The Mann-Whitney U-test was used. (B) Shows the number of neurones evoked at various current strengths to the dorsal root in both control and OA muscle afferent neurones.
Mentions: To determine the activation threshold of the dorsal root rectangular pulse stimuli were delivered at a current strength just sufficient to evoke an AP. This minimum activating current delivered from the dorsal root in control animals was 0.35±0.12 mA (N = 21), and was not different from that in OA animals, in which this value was 0.17±0.11 mA (N = 35; Mann-Whitney U-test, P = 0.1; Figure 4A). In control neurones, the percentage of neurones activated at various current strengths was shown as follows: 0.1 mA (23.8%), 0.2 mA (47.6%), 0.3 mA (14.3%), 0.5 mA (4.8%) and >0.5 mA (9.5%) There was also no difference in the composition of the number of neurones activated at different current strengths between control and OA animals (Chi-square test, P = 0.29; Figure 4B); in OA animals, the composition was: 0.1 mA (40%), 0.2 mA (52%), 0.3 mA (8%), and none for the 0.5 mA and >0.5 mA current strengths.

Bottom Line: Depolarizing intracellular current injection elicited more APs in models than in naïve muscle afferent neurones (P = 0.01) indicating greater excitability.The present study demonstrates changes in hind limb stance accompanied by changes in the functional properties of muscle afferent neurones in this derangement model of OA.This may provide a possible avenue to explore mechanisms underlying the impaired proprioceptive performance and perhaps other sensory disorders in people with OA.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada.

ABSTRACT

Background: Impaired proprioceptive performance is a significant clinical issue for many who suffer osteoarthritis (OA) and is a risk factor for falls and other liabilities. This study was designed to evaluate weight-bearing distribution in a rat model of OA and to determine whether changes also occur in muscle afferent neurones.

Methodology/principal findings: Intracellular recordings were made in functionally identified dorsal root ganglion neurones in acute electrophysiological experiments on the anaesthetized animal following measurements of hind limb weight bearing in the incapacitance test. OA rats but not naïve control rats stood with less weight on the ipsilateral hind leg (P = 0.02). In the acute electrophysiological experiments that followed weight bearing measurements, action potentials (AP) elicited by electrical stimulation of the dorsal roots differed in OA rats, including longer AP duration (P = 0.006), slower rise time (P = 0.001) and slower maximum rising rate (P = 0.03). Depolarizing intracellular current injection elicited more APs in models than in naïve muscle afferent neurones (P = 0.01) indicating greater excitability. Axonal conduction velocity in model animals was slower (P = 0.04).

Conclusions/significance: The present study demonstrates changes in hind limb stance accompanied by changes in the functional properties of muscle afferent neurones in this derangement model of OA. This may provide a possible avenue to explore mechanisms underlying the impaired proprioceptive performance and perhaps other sensory disorders in people with OA.

Show MeSH
Related in: MedlinePlus