Suppression and augmentation of trigeminal depressor response

脑血流量减少是牙科实践中最常见的并发症之一。三叉神经刺激起着重要作用，压力感受器反射似乎参与了这种并发症。因此，我们检测了刺激三叉神经和诱发动脉压力感受性反射时的血流动力学反应和自主神经活动(肾交感神经活动：RSNA，迷走神经活动：VNA)。此外，我们还观察了一些药物(异丙酚、芬太尼、异氟醚和酚妥拉明)对刺激三叉神经时血流动力学反应和自主神经活动的影响。刺激主动脉降压神经(ADN)诱发动脉压力感受性反射。低频刺激(5 Hz)眶下神经(ION)可显著降低平均动脉压(MAP)、心率(HR)和RSNA。高频离子刺激(25 Hz)引起双相改变，MAP提前下降，随后MAP上升。同时刺激ION(5 Hz)和ADN，观察动脉压力感受器反射的影响。同时刺激引起的降压反应大于单独离子刺激引起的降压反应。另一方面，在离子(25赫兹)和ADN刺激时，单独刺激离子时所观察到的升压反应被显著抑制。异丙酚抑制离子刺激时的降压反应，芬太尼呈剂量依赖性抑制降压反应。异丙酚和芬太尼联合应用可抑制降压和加压反应，但动脉压力感受器反射仍然存在。异氟醚抑制离子刺激时MAP和RSNA的变化，但离子刺激前MAP显著降低，动脉压力感受器反射受到抑制。酚妥拉明抑制降压反应，但RSNA的变化与给药前相似。

Decrease in cerebral blood flow is one of the most common complications in dental practice. Trigeminal stimulation plays an important role and baroreflex seems to participate in this complication. Therefore we examined hemodynamic responses and autonomic nerve activities (renal sympathetic nerve activity : RSNA, vagal nerve activity : VNA) when we stimulated trigeminal nerve and evoked arterial baroreflex. In addition, we examined effects of some agents (propofol, fentanyl, isoflurane and phentolamine) on hemodynamic response and autonomic nerve activity during stimuli of trigeminal nerve.This study was performed on rabbits. Arterial baroreflex was evoked with stimuli of aortic depressor nerve (ADN). Low frequency stimulation (5 Hz) of infraorbital nerve (ION) reduced mean arterial blood pressure (MAP), heart rate (HR) and RSNA significantly. High frequency stimulation (25 Hz) of ION caused a biphasic change, an early fall of MAP and a subsequent rise of MAP. Change of RSNA was also biphasic.To examine the effect of arterial baroreflex, simultaneous stimuli of ION (5 Hz) and ADN were performed. Depressor response evoked with simultaneous stimuli was greater than that evoked with ION alone. On the other hand, during stimuli of ION (25 Hz) and ADN, presser response which was observed during stimulation of ION alone was suppressed significantly. Change of RSNA was similar to the change of MAP.Propofol suppressed presser response during stimuli of ION and fentanyl suppressed depressor response in dosage dependence. Combination of propofol and fentanyl suppressed depressor and presser responses but arterial baroreflex still remained. Isoflurane suppressed changes of MAP and RSNA during stimuli of ION, but decrease in MAP before stimuli of ION was remarkable and arterial baroreflex was suppressed. Phentolamine suppressed presser and depressor response, but the change of RSNA was observed similarly before administration.