Sucrose-stimulated subsecond transient increase in cGMP level in rat intact circumvallate taste bud cells

Initial sweet tastetransduction is expected to occur in the subsecond time range. Wedemonstrate a rapid and transient (75-250 ms) increase of cGMP(but not cAMP) level in rat intact circumvallate taste cells afterstimulation by sucrose. This rapid increase does not occur innonsensory epithelial cells. Pretreatment with a nonspecificphosphodiesterase (PDE) inhibitor (IBMX), a specific cAMP-PDE4inhibitor (denbufylline), or an adenylyl cyclase activator (forskolin)all increased basal cAMP and abolished the sucrose-stimulated cGMPincrease at 150 ms. Pretreatment with a soluble guanylyl cyclaseinhibitor(1H-1,2,4]oxadiazolo4,3-a]quinoxalin-1-one) reduced, whereas a specific cGMP-PDE inhibitor (zaprinast) abolished, the sucrose-stimulated cGMP increase. It is proposed that cGMP isinvolved in the initial stage of sugar taste transduction and that cGMPis more significant than cAMP at this stage. Activation of solubleguanylyl cyclase and inhibition of cGMP-PDE may be involved in thetransient elevation of cGMP in response to sucrose stimulation.Moreover, it appears that cAMP level must remain low for sucrose tostimulate an increase in cGMP.