The taste of ethanol in a primate model. II. Glossopharyngeal nerve response in Macaca mulatta

The glossopharyngeal nerve (NG) mediates taste from the posterior part of t he tongue. Here, we studied the effects of ethanol on the tongue in recordi ngs from both the whole NG and individual taste fibers of the rhesus monkey , Macaca mulatta. The results show that the nerve activity increased at 0.7 M ethanol, reaching half maximum at around 4 M alcohol. Previously, we ide ntified three types of taste fibers in the rhesus monkey NG: S fibers predo minantly responding to sweeteners, Q fibers responding to bitter, such as q uinine hydrochloride (QHCl), and M fibers responding best to monosodium glu tamate, NaCl and acids [Hellekant, G., Danilova, V., & Ninomiya, Y. (1997). Primate sense of taste: behavioral and single chorda tympani and glossopha ryngeal nerve fiber recordings in the rhesus monkey, Macaca mulatta. J Neur ophysiol 77, 978-993]. Here, this fiber classification was used to elucidat e the oral effects of ethanol and ethanol mixtures with NaCl, sucrose, citr ic acid and QHCl. One and three molar concentrations of ethanol stimulated all fiber types. Mixtures of ethanol with QHCl elicited a smaller response in Q fibers than did QHCl alone. In S fibers, mixtures of ethanol with sucr ose gave a larger response than did sucrose alone. The variability of M fib ers was too large to allow a conclusion about the effect of ethanol. These results suggest that ethanol suppresses the taste of QHCl. Similarly, the t aste of sucrose might be enhanced by adding ethanol to sucrose. These effec ts and conclusions corroborate an earlier ethanol study of the chorda tympa ni (CT) nerve [Hellekant, G., Danilova, V., Roberts, T., & Ninomiya, Y. (19 97). The taste of ethanol in a primate model: I. Chorda tympani nerve respo nse in Macaca mulatta. Alcohol 14, 473-484]. (C) 2000 Elsevier Science Inc. All rights reserved.