A Comparative Study of Whole-Mouth Taste Thresholds between North Korean Refugees and South Koreans / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES@#Since Korea has been divided into two countries over 60 years ago and differences has gradually developed between the two, an influx of North Korean refugees to South Korea have soared over the past 20 years. Their complaints regarding taste intensity, particularly about strong sweetness of foods, are common after entry into South Korea. Because a long-term over-exposure or restriction to some taste stimuli causes profound alterations in corresponding taste sensitivity in humans, we hypothesized that sugar restriction, which remains common in North Korea, has influenced sweet sensitivity of North Koreans.SUBJECTS AND METHOD: To test this hypothesis, we assessed the taste stimuli recognition and detection thresholds of both young adults North refugees and South Koreans using a 1-mL whole-mouth gustatory test applied to a series of sweet, bitter, sour, and salty solutions.@*RESULTS@#As expected, the cumulative curve of the recognition threshold for sucrose shifted to the left and the mean recognition threshold for sucrose was significantly lower (0.5357% vs. 0.7393%, p=0.044) for North refugees than for South participants. On the other hand, the recognition threshold for salt was significantly higher (0.2174% vs. 0.1212%, p=0.027) in North refugees. No differences on the recognition taste sensitivity for quinine hydrochloride and citric acid were observed.@*CONCLUSION@#The findings documented in the present study indicate that a prolonged food deficit seems to have changed the taste sensitivity of healthy North Korean refugees. The altered taste sensitivity was most pronounced for sweet and salty tastes, and lasted up to 3.5 years after the refugees left North Korea.

Comparison of sucrose and ethanol-induced c-Fos-like immunoreactivity in the parabrachial nuclei and accumbens nucleus / 동물의과학연구지

Sucrose and alcohol are rewarding and appetitive. They are occasionally over-consumed and cause addiction. The parabrachial nuclei (PbN) are the second taste relay in the central taste pathway. The nucleus accumbens (NAcc) is an important neural substrate in the reward system. Intake of sucrose or alcohol induces dopamine release in the NAcc. Although alcohol is not classified as a taste stimulus, a substantial number of sucrose-responsive neurons in the PbN respond to stimulation by alcohol on the tongue. In the present study, we investigated whether or not application of 0.5 M sucrose, 10% ethanol (EtOH), mixture of sucrose and EtOH, and double-distilled water (DDW) to the tongue induces c-Fos-like immunoreactivity (cFLI) in the PbN and NAcc. We also examined whether or not the number of cFLI following sucrose/EtOH is comparable to the number of cFLIs following sucrose and EtOH, respectively. Male Sprague-Dwaley rat was anesthetized with a mixture of Zoletil and Rompun while stimulation solution was applied to the anterior tongue. The rat was sacrificed by perfusion, and the fixed brain was sectioned and immunostained. Data from a total of 18 animals were analyzed. The number of cFLI following stimulation with sucrose and/or EtOH was greater than that of DDW in the PbN. Numbers of cFLI following sucrose, EtOH, and sucrose/EtOH were not significantly different from each other in the PbN. The number of cFLI in response to stimulation solution was not different from that of DDW in the NAcc. The result of the present study suggests that not only sucrose but also EtOH activates some neurons in the PbN, and that some pontine neurons possibly respond to both sucrose and EtOH.

c-Fos-like Immunoreactivity in the nucleus of the solitary tract following taste stimulation of the contralateral side of the tongue / 동물의과학연구지

Taste receptors of the anterior tongue are innervated by the chorda tympani (CT) branch of the facial (VIIth) nerve. The CT nerve transmits information on taste to the ipsilateral nucleus of the solitary tract (NST), which is the first taste central nucleus in the medulla. Taste information is known to be transferred ipsilaterally along the taste pathway in the central nervous system. Some patients with unilateral CT damage often retain their ability to sense taste. This phenomenon is not explained by the unilateral taste pathway. We examined whether neurons in the NST receive information on taste from the contralateral side of the tongue by measuring c-Fos-like Immunoreactivity (cFLI) following taste stimulation of the contralateral side of the tongue in the anesthetized rats. We used four basic taste stimuli, 1.0 M sucrose, 0.3 M NaCl, 0.01 M citric acid, 0.03 M QHCl, and distilled water. Stimulation of one side of the tongue with taste stimuli induced cFLI in the NST bilaterally. The mean number of cFLI ranged from 23.28 +/- 2.46 by contralateral QHCl to 30.28 +/- 2.26 by ipsilateral NaCl stimulation. The difference between the number of cFLI in the ipsilaterl and contralateral NST was not significant. The result of the current study suggests that neurons in the NST receive information on taste not only from the ipsilateral but also the contralateral side of the tongue.