The formation of chemical cellular signals in response to taste stimulation may be initiated in sub-second time range. We are using a Quench Flow Module (QFM) and a Fast Pippeting System (FPS) to monitor cellular signals in rat taste tissue homogenates and intact cells in response to bitter taste stimulants that are important to the acceptance of agricultural food products. Stimulation by grape-derived catechin and the citrus-derived naringin increased the formation of the IP_3 signal with parallel decline of cAMP. Under similar experimental conditions, the citrus-derived limonin reduced cAMP whereas casein-derived cyclo(Leu-Trp) bitter dipeptide produced a rapid and transient increase of cAMP. cGMP was not affected by any of the four stimuli. These results further emphasize the presence of multiple transduction pathways and modulation of two parallel second messengers in bitter taste sensation of some bitter compounds.
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