THE PARASYMPATHETIC VASODILATOR FIBERS IN THE TRIGEMINAL PORTION OF THE DISTAL LINGUAL NERVE IN THE CAT TONGUE

Electrical stimulation of the peripheral and central cut ends of the chorda tympani nerve (CTN) caused an increase in ipsilateral tongue blood flow in anesthetized cats. Both blood flow increases were markedly reduced by pretreatment with the autonomic ganglionic blocker hexamethonium (1.0 mg/kg). Electrical stimulation of the central cut ends of the CTN, inferior alveolar nerve, and vagus nerve as well as of the upper buccal gingiva also caused the vasodilator responses in the sympathectomized cat tongue. These vasodilatations were notably reduced by hexamethonium pretreatment, and were almost completely abolished by the section of the distal lingual nerve (DLN) and the lingual nerve proper but not by section of the CTN. The present data suggest that the parasympathetic vasodilator fibers in the CTN are not involved in somatoautonomic reflex vasodilatation in the cat tongue and that the major part of the somatoautonomic reflex vasodilator response is mediated by parasympathetic fibers running together with the trigeminal portion of the DLN as vasodilator fibers in the cat tongue. This also implies that there are two groups of parasympathetic vasodilator fibers, that is, one originates from the CTN (the facial nerve) and other from the trigeminal portion of the DLN (probably via the glossopharyngeal nerve).