抄録
The present study was designed to examine 1) whether there are vasodilator fibers in the masticatory muscles, and 2) if there are, to establish the neurogenic nature of the responses in deeply urethane-anesthetized, artificially ventilated rats. Electrical stimulations of the central cut ends of either the lingual nerve (LN) or the mental nerve elicited intensity- and frequency-dependent increases in the blood flow in the masseter muscle (MBF), the digastric muscle (DBF) and lower lip (LBF). Increases in the MBF, DBF and LBF were reduced by hexamethonium (autonomic ganglion blocker) in a dose-dependent manner. Pretreatment with phentolamine, or propranolol and the section of the superior cervical sympathetic trunk had no effect on these responses. However, atropine pretreatment statistically significantly reduced the increases in the MBF and DBF, but not in LBF. When WGA-HRP was injected into the masseter muscle, labeled neurons were abundantly observed in the otic ganglion. These results indicate that there are parasympathetic cholinergic vasodilator fibers originated from cell bodies in otic ganglion in the rat masticatory muscles. The increases evoked by activation of the parasympathetic fibers occurred by the trigeminal mediated reflex, suggesting that the novel parasympathetic vasodilator response may play an important role in the regulation of the hemodynamics of masticatory muscles. [Jpn J Physiol 55 Suppl:S196 (2005)]
