Decreased face primary motor cortex (face-M1) excitability induced by noxious stimulation of the rat molar tooth pulp is dependent on the functional integrity of medullary astrocytes

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• 作者：H. Pun ; L. Awamleh ; J.-C. Lee ; L. Avivi-Arber
• 关键词：Neuroplasticity ; Dental ; Pain ; Brainstem ; Intracortical microstimulation ; Glia
• 刊名：Experimental Brain Research
• 出版年：2016
• 出版时间：March 2016
• 年：2016
• 卷：234
• 期：3
• 页码：645-657
• 全文大小：1,077 KB
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• 作者单位：H. Pun (1)
  L. Awamleh (1)
  J.-C. Lee (1)
  L. Avivi-Arber (1) (2)
  
  1. Department of Oral Physiology, Faculty of Dentistry, University of Toronto, Toronto, ON, Canada
  2. Department of Prosthodontics, Faculty of Dentistry, University of Toronto, 124 Edward St., Toronto, ON, M5G1G6, Canada
  
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Biomedicine
  Neurosciences
  Neurology
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1432-1106

文摘

We have recently shown that application of the small-fiber excitant and inflammatory irritant mustard oil (MO) to the rat molar tooth pulp can decrease face-M1 excitability, but increase the excitability of trigeminal medullary dorsal horn (MDH) nociceptive neurons and that application of the astrocytic inhibitor methionine sulfoximine (MSO) to the face-M1 or MDH can attenuate the MO-induced changes. The present study aimed to determine whether medullary MSO application could modulate the MO-induced decreased face-M1 excitability. Under ketamine general anesthesia, electromyographic (EMG) electrodes were implanted into the right anterior digastric (RAD, jaw-opening muscle) of adult male Sprague–Dawley rats. A microelectrode was positioned at a low-threshold (≤30 μA) site in the left face-M1. Then MO (n = 16) or control-solution (n = 16) was applied to the previously exposed molar tooth pulp, and intracortical microstimulation threshold intensities for evoking RAD EMG activities were monitored for 15 min. MSO (0.1 mM, n = 8) or phosphate-buffered saline (PBS, n = 8) was then applied to the MDH and RAD thresholds monitored every 15 min for 120 min. Statistics used ANOVA followed by post hoc Bonferroni as appropriate (p < 0.05). As compared to baseline, RAD thresholds significantly increased (i.e., decreased excitability) within 1 min (26.3 ± 7.9 %, p = 0.007) and peaked at 15 min following pulpal MO application (49.9 ± 5.7 %, p < 0.001) but not following control-solution. Following MSO (but not PBS) application to the medulla, RAD thresholds significantly decreased within 15 min (26.5 ± 3.0 %, p = 0.05) and at 60 min approached 6.3 ± 2.4 %, of baseline values (p = 0.1). These novel findings suggest that clinically related motor disturbances arising from dental pain may involve decreased face-M1 excitability that is modulated by medullary astrocytes. Keywords Neuroplasticity Dental Pain Brainstem Intracortical microstimulation Glia