Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, Canada.
Department of Anesthesia, Pharmacology and Therapeutics, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada.
J Oral Rehabil. 2024 Oct;51(10):1997-2007. doi: 10.1111/joor.13787. Epub 2024 Jun 18.
Activation of β adrenergic receptors reduces cutaneous mechanical pain thresholds in rats. While β adrenergic receptor activation may contribute to mechanisms that underlie temporomandibular joint pain, its effect on masticatory muscle pain sensitivity is uncertain.
The current study sought to determine the extent to which β adrenergic receptors are expressed by masticatory muscle afferent fibres, and to assess the effect of local activation of these receptors on the mechanical sensitivity of masticatory muscle afferent fibres in rats.
Trigeminal ganglion neurons that innervate the rat (n = 12) masseter muscle and lower lip were identified by tissue injection of fluorescent dyes and were then stained with antibodies against β or β adrenergic receptors. Extracellular recordings from 60 trigeminal ganglion neurons that innervate the masticatory muscle were undertaken in a second group of anaesthetised rats of both sexes (n = 37) to assess afferent mechanical activation thresholds. Thresholds were assessed before and after injection of the β adrenergic receptor agonists into masticatory muscle.
β and β adrenergic receptor expression was greater in labial skin than in masticatory muscle ganglion neurons (p < .05, one-way ANOVA, Holm-Sidak test). There was a higher expression of β adrenergic receptors in masticatory muscle ganglion neurons in males than in females. The mixed β agonist isoproterenol increased afferent mechanical activation threshold in male but not female rats (p < .05, Mann-Whitney test). In male rats, salbutamol, a β selective agonist, also increased afferent mechanical activation threshold but hydralazine, a vasodilator, did not (p < .05, Mann-Whitney test).
Activation of β adrenergic receptors decreases the mechanical sensitivity of masticatory muscle afferent fibres in a sex-related manner.
β肾上腺素能受体的激活会降低大鼠皮肤的机械痛觉阈值。虽然β肾上腺素能受体的激活可能有助于解释颞下颌关节疼痛的机制，但它对咀嚼肌疼痛敏感性的影响尚不确定。
本研究旨在确定咀嚼肌传入纤维中β肾上腺素能受体的表达程度，并评估局部激活这些受体对大鼠咀嚼肌传入纤维机械敏感性的影响。
通过向组织内注射荧光染料，鉴定出支配大鼠（n=12）咬肌和下唇的三叉神经节神经元，然后用β或β肾上腺素能受体抗体对其进行染色。在另一组麻醉的雌雄两性大鼠（n=37）中，从 60 个支配咀嚼肌的三叉神经节神经元中进行了细胞外记录，以评估传入机械激活阈值。在向咀嚼肌注射β肾上腺素能受体激动剂之前和之后评估阈值。
唇部皮肤中β和β肾上腺素能受体的表达高于咀嚼肌神经节神经元（p<0.05，单因素方差分析， Holm-Sidak 检验）。咀嚼肌神经节神经元中β肾上腺素能受体的表达在雄性大鼠中高于雌性大鼠。混合β激动剂异丙肾上腺素增加了雄性大鼠但不增加雌性大鼠的传入机械激活阈值（p<0.05，Mann-Whitney 检验）。在雄性大鼠中，β选择性激动剂沙丁胺醇也增加了传入机械激活阈值，但血管扩张剂肼屈嗪没有（p<0.05，Mann-Whitney 检验）。
β肾上腺素能受体的激活以性别相关的方式降低了咀嚼肌传入纤维的机械敏感性。
