pISSN 1226-4512 eISSN 2093-3827

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Original Article

Korean J Physiol Pharmacol 2021; 25(6): 603-611

Published online November 1, 2021 https://doi.org/10.4196/kjpp.2021.25.6.603

Copyright © Korean J Physiol Pharmacol.

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

Cheng-Shu Li1, Ki-Myung Chung2, Kyung-Nyun Kim2, and Young-Kyung Cho2,*

1Department of Anatomy, School of Medicine, Southern Illinois University, Carbondale, IL 62901, USA, 2Department of Physiology and Neuroscience, College of Dentistry and Research Institute of Oral Science, Gangneung-Wonju National University, Gangneung 25457, Korea

Correspondence to:Young-Kyung Cho
E-mail: ykcho@gwnu.ac.kr

Received: August 3, 2021; Revised: September 3, 2021; Accepted: September 13, 2021

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Copyright © Korean J Physiol Pharmacol, pISSN 1226-4512, eISSN 2093-3827

Abstract

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 (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°C dH2O-and between 25% EtOH- and 40°C 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°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.

Keywords: Electrophysiology, Ethanol, In vivo, Solitary nucleus, Sucrose