New apparatus stimulating the region of tongue innervated by glossopharyngeal nerve and its application to monosodium glutamate (MSG) solution.

Some apparatuses stimulating the region of tongue innervated by chorda tympani nerve were well known and they were used popularly, but the apparatuses for glossopharyngeal nerve were not produced yet. In the study, the apparatus for the stimulations of glossopharyngeal nerve was trially produced. It was known that the substance of "Umami" was responded well in the tongue region innervated by glossopharyngeal nerve. The evoked potential for the stimulations of monosodium glutamate (MSG) solution which was known as substance of Umami was measured with the use of the trial stimulating apparatus. The evoked potential was detected by monopolar lead for the positions between Cz and A1 (left lobe) with the ground at Fpz. The evoked potential of MSG consisted of a positive peak wave with the latency at approximately 250 ms. The amplitudes increased and the latency decreased as the concentration of MSG increased. The evoked potential stimulating the tongue innervated by this glossopharyngeal nerve could be detected for the first time by the use of the trial apparatus.