Taste signal transduction occurs in the microvillous membrane of taste cells. Previously, we hypothesized that c-GMP may mediate sweet taste transduction. Some data indicated that IP3 may have a role in vertebrate bitter taste transduction. Here we report that the different second messengers are activated by different tastes. We used techniques designed for radioimmunoassay measurement. The results indicate that sucrose triggers an increase in c-GMP concentration and quinine increases the IP3 concentration in mouse taste cells. These results support the sweet and bitter taste transduction hypotheses.