Exp Neurobiol 2007; 16(2): 79-87
Published online December 31, 2007
© The Korean Society for Brain and Neural Sciences
Young Kyung Cho*
Department of Physiology and Neuroscience, Kangnung National University College of Dentistry, Gangneung 210-702, Gangwon, Korea; Department of Anatomy, Southern Illinois University School of Medicine, Carbondale, IL 62901, USA
Correspondence to: *To whom correspondence should be addressed.
TEL: 1-618-303-6895, FAX: 1-618-453-1527
Alcohol usually refers to ethanol which is one of widely consumed beverages and is sometimes being abused. One of the factors that induce alcohol intake is taste. Previous investigations reported that alcohol activated gustatory nerves and neurons in the nucleus of the solitary tract (NST). Alcohol preference is closely related to liking for sweet taste. Taste neurons often respond to thermal or mechanical stimulation. The parabrachial nuclei (PbN) in the pons are the second taste relay in the rodent. Gustatory responses of taste neurons in the NST and PbN are modulated by several physiological factors related to ingestive behavior. The purpose of the present study was to investigate the relationship of ethanol (EtOH) response to sucrose response and temperature of the solution in the hamster PbN. In the first set of experiment, 55 gustatory PbN neurons recorded extracellularly in the urethane-anesthetized hamster, in response to four basic taste stimuli, 25% EtOH, 40oC and 4oC distilled water. The 32, 28, and 36 neurons responded to 25% EtOH, 40oC and 4oC distilled water, respectively. The response to 25% EtOH was positively related to sucrose response (r=0.82, p＜0.001). In the second set of experiment, 30 sucrose-sensitive neurons in the PbN were recorded, in response to a series of EtOH concentrations (3∼40%) alone and mixtures with 32 mM sucrose at room temperature (RT), 40oC and 4oC. Neuronal responses to EtOH at RT and 40oC increased as the concentration was raised. The response to a mixture of EtOH and sucrose was greater than EtOH or sucrose response alone. The responses of EtOH alone or EtOH/sucrose were enhanced by applying solution at 40oC but were flatten at 4oC. These data demonstrate that EtOH activates the sucrose-responsive taste neurons in the PbN and that this interaction is affected by temperature.
Keywords: ethanol, sucrose, thermal stimulation, gustatory neuron, parabrachial nuclei, in vivo electrophysiology