| Budget Amount *help |
¥4,400,000 (Direct Cost: ¥4,400,000)
Fiscal Year 1991: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1990: ¥4,000,000 (Direct Cost: ¥4,000,000)
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| Research Abstract |
The sensation of taste caused by taste is producesd by a chemo-electrical signal transduction process, which upon specific interaction of taste with receptor cells leads to a membrane depolarization. Several mechanisms have been proposed to explain taste transduction, including direct taste gated permeability changes, compelling evidence has been accumulated suggesting that c-GMP, C-AMP and/or IP-, serves as an intracellular messenger in this process. Although the stimulation of c^3-GMP by taste is an attractive scheme for mediating taste transduction. It is questionable Whether this mechanien is responsible for detection of all tastes, or whether different second messenger pathways are involved. Recent electrophysiological study suggests that there is a positive correlation between the magnitudeof C-GMP activation and the amplitude of the receptor potential induced by sweet taste. From the result, it has been concluded that c-GMP activity is a key element in taste transduction. Furthe
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rmore it was also proposed that bitter taste caused an increase of IP_3 concentration. These studies demonstrated that each taste can activate alternative second messenger pathways in the taste transduction. However, their relation to the taste transduction process is unclear. One important criterion for a candidate second messenger of taste transduction is that its formation must accompany by the onset of the taste stimulus. In order to approach the question if the type of second messenger system that is activated can be correlated to taste qualities, individual tastes from sweet, bitter, sour and salt have been assayed for their potential to activate either the c-GMP or the IP_3-pathway- Radio-immuno assay methods are appropriate to understand cellular taste transduction properties whereas, such transduction may be missed when looking at properties of intracellular potentials and single channels.
It is a question whether a transduction mechanism is responsible for detection of all tastes, or whether different second messenger pathways are involved. One important criterion for a candidate second messenger of taste transduction is that its formation must accompany by the onset of the taste stimulus. This study demonstrated that the primary four taste qualities were assayed for their potential to activate second messenger pathways using radioimmuno assay technique in taste cells from mouse tongue. It was found that each taste does not all activate the same second messenger. Sucrose increased the concentration of c-GMP and quinine increased the concentration of IP_3. Less
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