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α₁ Adrenergic Receptor Activation has a Dynamic Effect on Masticatory Muscle Afferent Fibers Benbow, Tarique; Ranjbar-Ekbatan, Maryam; Cairns, Brian E.
Abstract
Temporomandibular Disorder (TMD) patients report amplification of pain in the masticatory muscles after psychological trauma or stressful conditions. The mechanisms underlying this phenomenon are yet to be elucidated. This study combined immunohistochemistry with single cell in vivo electrophysiology recordings of masticatory muscle afferent fibers to investigate the role of α₁-adrenergic receptors in muscle nociception. It was found that a subset of trigeminal afferent fibers which innervate the masseter and temporal muscles expressed α₁α, α₁b and α₁d receptors, including a smaller number of putative nociceptors which co-expressed TrpV₁ receptors. Local injection of the selective α₁ adrenergic receptor agonist phenylephrine into masticatory muscle decreased and increased the mechanical activation threshold of slow and fast conducting afferent fibers, respectively. This effect was reversed by co-administration of the α1 selective antagonist terazosin. To rule out the possibility that local ischemia was responsible for the observed effect of phenylephrine on masticatory muscle afferent fibers, additional experiments were conducted where blood flow to the masticatory muscle was reduced by common carotid artery occlusion. This investigation found that muscle blood flow occlusion increased the mechanical activation threshold of the majority of masticatory muscle afferent fibers unrelated to conduction velocity. These findings suggest that under conditions of increased sympathetic tone, such as those related to stress, noradrenaline may sensitize masticatory muscle nociceptors to increase pain and desensitize muscle proprioceptors to alter muscle tone, through activation of α1 receptors.
Item Metadata
Title |
α₁ Adrenergic Receptor Activation has a Dynamic Effect on Masticatory Muscle Afferent Fibers
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Creator | |
Publisher |
Elsevier
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Date Issued |
2020-06-20
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Description |
Temporomandibular Disorder (TMD) patients report amplification of pain in the masticatory
muscles after psychological trauma or stressful conditions. The mechanisms underlying this
phenomenon are yet to be elucidated. This study combined immunohistochemistry with single cell
in vivo electrophysiology recordings of masticatory muscle afferent fibers to investigate the role
of α₁-adrenergic receptors in muscle nociception. It was found that a subset of trigeminal afferent
fibers which innervate the masseter and temporal muscles expressed α₁α, α₁b and α₁d receptors,
including a smaller number of putative nociceptors which co-expressed TrpV₁ receptors. Local
injection of the selective α₁ adrenergic receptor agonist phenylephrine into masticatory muscle
decreased and increased the mechanical activation threshold of slow and fast conducting afferent
fibers, respectively. This effect was reversed by co-administration of the α1 selective antagonist
terazosin. To rule out the possibility that local ischemia was responsible for the observed effect of
phenylephrine on masticatory muscle afferent fibers, additional experiments were conducted
where blood flow to the masticatory muscle was reduced by common carotid artery occlusion.
This investigation found that muscle blood flow occlusion increased the mechanical activation
threshold of the majority of masticatory muscle afferent fibers unrelated to conduction velocity.
These findings suggest that under conditions of increased sympathetic tone, such as those related
to stress, noradrenaline may sensitize masticatory muscle nociceptors to increase pain and
desensitize muscle proprioceptors to alter muscle tone, through activation of α1 receptors.
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Subject | |
Genre | |
Type | |
Language |
eng
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Date Available |
2022-08-08
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Provider |
Vancouver : University of British Columbia Library
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Rights |
Attribution-NonCommercial-NoDerivatives 4.0 International
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DOI |
10.14288/1.0416615
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URI | |
Affiliation | |
Citation |
Benbow T, Ranjbar Ekbatan M, Cairns BE. α1 adrenergic receptor activation has a dynamic effect on masticatory muscle afferent fibers. Neuropharmacology 2020;175:108197
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Publisher DOI |
10.1016/j.neuropharm.2020.108197
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Peer Review Status |
Reviewed
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Scholarly Level |
Faculty; Graduate
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Rights URI | |
Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
Attribution-NonCommercial-NoDerivatives 4.0 International