Division of Physiology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido, Japan.
Division of Pediatric Dentistry, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido, Japan.
Microvasc Res. 2021 Nov;138:104214. doi: 10.1016/j.mvr.2021.104214. Epub 2021 Jul 1.
Skeletal muscle hemodynamics, including that in jaw muscles, is an important in their functions and is modulated by aging. Marked blood flow increases mediated by parasympathetic vasodilation may be important for blood flow in the masseter muscle (MBF); however, the relationship between parasympathetic vasodilation and aging is unclear. We examined the effect of aging on parasympathetic vasodilation evoked by trigeminal afferent inputs and their mechanisms by investigating the MBF during stimulation of the lingual nerve (LN) in young and old urethane-anesthetized and vago-sympathectomized rats. Electrical stimulation of the central cut end of the LN elicited intensity- and frequency-dependent increases in MBF in young rats, while these increases were significantly reduced in old rats. Increases in the MBF evoked by LN stimulation in the young rats were greatly reduced by hexamethonium and atropine administration. Increases in MBF in young rats were produced by exogenous acetylcholine in a dose-dependent manner, whereas acetylcholine did not influence the MBF in old rats. Significant levels of muscarinic acetylcholine receptor type 1 (MR1) and type 3 (MR3) mRNA were observed in the masseter muscle in young rats, but not in old rats. Our results indicate that cholinergic parasympathetic reflex vasodilation evoked by trigeminal afferent inputs to the masseter muscle is reduced by aging and that this reduction may be mediated by suppression of the expression of MR1 and MR3 in the masseter muscle with age.
骨骼肌的血液动力学，包括咀嚼肌的血液动力学，在其功能中很重要，并受衰老的调节。由副交感神经舒张介导的明显的血流增加可能对咬肌（MBF）的血流很重要；然而，副交感神经舒张与衰老之间的关系尚不清楚。我们通过研究在年轻和老年乌拉坦麻醉和迷走神经切断的大鼠中刺激舌神经（LN）时的 MBF，研究了衰老对三叉神经传入输入引起的副交感神经舒张的影响及其机制。在年轻大鼠中，LN 中枢端的电刺激引起 MBF 呈强度和频率依赖性增加，而在老年大鼠中这些增加则明显减少。在年轻大鼠中，LN 刺激引起的 MBF 增加被六烃季铵和阿托品给药大大减少。在年轻大鼠中，外源性乙酰胆碱以剂量依赖性方式产生 MBF 增加，而乙酰胆碱对老年大鼠的 MBF 没有影响。在年轻大鼠的咬肌中观察到显著水平的毒蕈碱乙酰胆碱受体 1（MR1）和 3（MR3）mRNA，但在老年大鼠中没有。我们的结果表明，咀嚼肌三叉神经传入输入引起的胆碱能副交感神经反射性血管舒张随年龄而减少，这种减少可能是由于随着年龄的增长，MR1 和 MR3 在咬肌中的表达受到抑制所致。
