Abstract
Objectives: Previous research has shown that submaximal mouth opening by mandibular extension (ME) is followed by a prolonged reduction in blood pressure. This effect was observed in young and adult normotensive and hypertensive rats and in young normotensive human subjects. Methods: We assessed the effects of a ME for 10 minutes obtained with a fixed mouth opener in both hypertensive adult humans (aged 55 years or older) and elderly (6-7 months) anaesthetized, hypertensive rats (SHR). Blood pressure and heart rate were measured every 10 minutes by non-invasive automatic recorders for 30 minutes before and 120 minutes after the procedure. Nine human hypertensive subjects (7 experimental and 2 controls) and seven spontaneously hypertensive rats (5 experimental and 2 controls) were tested. Results: A statistically significant reduction in systolic blood pressure (SBP), mean arterial blood pressure (MABP) and heart rate (HR) was observed after ME in the seven hypertensive human subjects, in whom an average decrease of 15 mmHg for SBP, 10 mmHg for MABP and 7 bpm for HR, was observed. A similar hypotensive effect was recorded in spontaneously hypertensive rats that displayed a statistically significant decrease of SBP, DBP and MABP, amounting to about 40-50 mmHg. Conclusion: This study provides the first evidence that ME has an important and prolonged hypotensive effect when applied to subjects with high blood pressure, making their arterial blood pressure decrease toward normal values for at least two hours.
Highlights
Several studies, starting from the pioneering work by Kumada and coworkers in rabbits have shown that manipulation of the facial region through electrical stimulation of the trigeminal system or maxillofacial surgery can elicit a reflex leading to a sudden onset of a number of physiological responses including bradycardia, hypotension, apnea and gastric hypermotility [1, 2]
Our research group has built upon these observations to demonstrate that a reduction of arterial blood pressure and heart rate could be obtained through a non-invasive technique consisting of a prolonged opening of the mouth, which we called mandibular extension (ME)
We have observed that ME is followed by a prolonged decline in mean blood pressure in rats in which hypertension was induced by dexamethasone administration (20 μg/kg/day, subcutaneously for 7 days) and in spontaneously hypertensive rats (SHR)
Summary
Several studies, starting from the pioneering work by Kumada and coworkers in rabbits have shown that manipulation of the facial region through electrical stimulation of the trigeminal system or maxillofacial surgery can elicit a reflex leading to a sudden onset of a number of physiological responses including bradycardia, hypotension, apnea and gastric hypermotility [1, 2]. Mandibular Extension in Hypertensive Rats and Humans mmHg in mean arterial blood pressure was observed and a less marked hypotensive effect in normotensive young human subjects [6,7,8,9,10]. We have observed that ME is followed by a prolonged decline in mean blood pressure in rats in which hypertension was induced by dexamethasone administration (20 μg/kg/day, subcutaneously for 7 days) and in spontaneously hypertensive rats (SHR). In both cases, the treatment induced a marked reduction in mean arterial blood pressure, which was much greater compared to that observed in normotensive rats [11]
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