| Budget Amount *help |
¥13,600,000 (Direct Cost: ¥13,600,000)
Fiscal Year 2004: ¥3,900,000 (Direct Cost: ¥3,900,000)
Fiscal Year 2003: ¥4,400,000 (Direct Cost: ¥4,400,000)
Fiscal Year 2002: ¥5,300,000 (Direct Cost: ¥5,300,000)
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| Research Abstract |
In Drosophila, gustatory receptor neurons (GRNs) occur within hair-like structures called sensilla located on prothoracic legs and labellum. Most taste sensilla house four GRNs, which have been named according to their preferred sensitivity to basic stimuli : water (W cell), sugars (S cell), salt at low concentration (L1 cell), and salt at high concentration (L2 cell). We showed for the first time that several taste sensilla on the prothoracic legs detect bitter compounds both through the activation of specific taste neurons but also through inhibition of taste neurons activated by sugars and water. Using a new statistical approach based on the analysis of interspike intervals, we showed that bitter compounds activate the L2 cell. Their sensitivity to bitter compounds was different between sensilla, suggesting that specific receptors to bitter compounds are differentially expressed among L2 cells. Labellar taste sensilla are classified into three types, l-,s-, and i-type, according to their length and location. We recorded the nerve responses from all the three types of sensilla to sugars, salts and bitter compound. We found that s- and i-type sensilla respond to bitter compounds. l- and s-type labellar sensilla possess four cells, while most i-type sensilla house only two GRNs. In i-type sensilla, we demonstratd that the first GRN responds to sugar and to low concentrations of salt. The second GRN detects a range of bitter compounds, among which strychnine is the most potent ; and also to salt at high concentrations. Neither type of GRN responds to water
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