Site-specific autonomic vasomotor responses and their interactions in rat gingiva

Blood flow in the gingiva, comprising the interdental papilla as well as attached and marginal gingiva, is important for maintaining of gingival function and is modulated by risk factors such as stress that may lead to periodontal disease. Marked blood flow changes mediated by the autonomic (parasympathetic and sympathetic) nervous system may be essential for gingival hemodynamics. However, differences in autonomic vasomotor responses and their functional significance in different parts of the gingiva are unclear. We examined the differences in autonomic vasomotor responses and their interactions in the gingiva of anesthetized rats. Parasympathetic vasodilation evoked by the trigeminal (lingual nerve)-mediated reflex elicited frequency-dependent blood flow increases in gingivae, with the increases being greatest in the interdental papilla. Parasympathetic blood flow increases were significantly reduced by intravenous administration of the atropine and VIP antagonist. The blood flow increase evoked by acetylcholine administration was higher in the interdental papilla than in the attached gingiva, whereas that evoked by VIP agonist administration was greater in the attached gingiva than in the interdental papilla. Activation of the cervical sympathetic nerves decreased gingival blood flow and inhibited parasympathetically induced blood flow increases. Our results suggest that trigeminal-parasympathetic reflex vasodilation 1) is more involved in the regulation of blood flow in the interdental papilla than in the other parts of the gingiva, 2) is mediated by cholinergic (interdental papilla) and VIPergic systems (attached gingiva), and 3) is inhibited by excess sympathetic activity. These results suggest a role in the etiology of periodontal diseases during mental stress.