Response properties of the pharyngeal branch of the glossopharyngeal nerve for umami taste in mice and rats.
Many studies have reported the mechanism underlying umami taste. However, there are no investigations of responses to umami stimuli taste originating from chemoreceptors in the pharyngeal region. The pharyngeal branch of the glossopharyngeal nerve (GPN-ph) innervating the pharynx has unique responses to taste stimulation that differs from responses of the chorda tympani nerve and lingual branch of the glossopharyngeal nerve. Water evokes robust response, but NaCl solutions at physiological concentrations do not elicit responses. The present study was designed to examine umami taste (chemosensory) responses in the GPN-ph. Response characteristics to umami taste were compared between mice and rats. In mice, stimulation with compounds eliciting umami taste (0.1M monosodium L-glutamate (MSG), 0.01M inosine monophosphate (IMP) and the mixture of 0.1M MSG+0.01M IMP) evoked higher responses than application of distilled water (DW). However, synergistic response of a mixture of 0.1M MSG+0.01M IMP was not observed. In rats, there is no significant difference between the responses to umami taste (0.1M MSG, 0.01M IMP and the mixture of 0.1M MSG+0.01M IMP) and DW. Monopotassium glutamate (MPG) was used in rats to examine the contribution of the sodium component of MSG on the response. Stimulation with 0.1M MPG evoked a higher response when compared with responses to DW. The present results suggest that umami taste compounds are effective stimuli of the chemoreceptors in the pharynx of both mice and rats.
Kitagawa
Junichi
J
Department of Physiology, Nippon Dental University, School of Life Dentistry at Tokyo, 1-9-20 Fujimi-cho, Chiyoda-ku, Tokyo 102-8159, Japan. kitagawa-j@tokyo.ndu.ac.jp
Takahashi
Yoshihiro
Y
Matsumoto
Shigeji
S
Shingai
Tomio
T
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D004347:Drug Interactions / Q000502:physiology; D005930:Glossopharyngeal Nerve / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D007291:Inosine Monophosphate / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology; D010614:Pharynx / Q000187:drug effects / Q000294:innervation* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012970:Sodium Glutamate / Q000378:metabolism / Q000494:pharmacology; D013045:Species Specificity; D013649:Taste / Q000187:drug effects / Q000502:physiology*; D013650:Taste Buds / Q000187:drug effects / Q000502:physiology*; D017833:Visceral Afferents / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology
D007291:Inosine Monophosphate; D012970:Sodium Glutamate