Influences of ethanol and temperature on sucrose-evoked response of gustatory neurons in the hamster solitary nucleus

• Published in: The Korean journal of physiology & pharmacology 2021-11, Vol.25 (6), p.603-611
• Main Authors: Li, Cheng-Shu, Chung, Ki-Myung, Kim, Kyung-Nyun, Cho, Young-Kyung
• Format: Article
• Language: Korean
• ISSN: 1226-4512; 2093-3827

Taste-responsive neurons in the nucleus of the solitary tract (NST), the first gustatory nucleus, often respond to thermal or mechanical stimulation. Alcohol, not a typical taste modality, is a rewarding stimulus. In this study, we aimed to investigate the effects of ethanol (EtOH) and/or temperature as stimuli to the tongue on the activity of taste-responsive neurons in hamster NST. In the first set of experiments, we recorded the activity of 113 gustatory NST neurons in urethane-anesthetized hamsters and evaluated responses to four basic taste stimuli, 25% EtOH, and 40℃ and 4℃ distilled water (dH2O). Sixty cells responded to 25% EtOH, with most of them also being sucrose sensitive. The response to 25% EtOH was significantly correlated with the sucrose-evoked response. A significant correlation was also observed between sucrose- and 40℃ dH2O- and between 25% EtOH- and 40℃ dH2O-evoked firings. In a subset of the cells, we evaluated neuronal activities in response to a series of EtOH concentrations, alone and in combination with 32 mM sucrose (EtOH/Suc) at room temperature (RT, 22℃-23℃), 40℃, and 4℃. Neuronal responses to EtOH at RT and 40℃ increased as the concentrations increased. The firing rates to EtOH/Suc were greater than those to EtOH or sucrose alone. The responses were enhanced when solutions were applied at 40℃ but diminished at 4℃. In summary, EtOH activates most sucrose-responsive NST gustatory cells, and the concomitant presence of sucrose or warm temperatures enhance this response. Our findings may contribute to elucidate the neural mechanisms underlying appetitive alcohol consumption.