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 Vol. 25; no. 6; pp. 603 - 611
• Main Authors: Li, Cheng-Shu, Chung, Ki-Myung, Kim, Kyung-Nyun, Cho, Young-Kyung
• Format: Journal Article
• Language: English
• Published: The Korean Physiological Society and The Korean Society of Pharmacology 01.11.2021; 대한약리학회
• Subjects: Original; 약리학
• ISSN: 1226-4512; 2093-3827
• DOI: 10.4196/kjpp.2021.25.6.603

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°C and 4°C distilled water (dH 2 O). 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°C dH 2 O- and between 25% EtOH- and 40°C dH 2 O-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°C–23°C), 40°C, and 4°C. Neuronal responses to EtOH at RT and 40°C 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°C but diminished at 4°C. 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.