This study has demonstrated that (1) Bitter sensitive taste cells are heterogeneous from the point of view of their responsiveness, (2) Overall response profile of bitter taste cells to multiple bitter compounds was not significantly different between fungiform and circumvallate papillae, (3) Bitter responses of taste cells were significantly suppressed by TRPM5 inhibitor and PLC inhibitor, (4) Bitter responses of mouse taste cells were not affected by human bitter receptor antagonists, (5) CCK may be involved in peripheral bitter taste signaling. These data help understanding receptors and transduction mechanisms for bitter taste and give insights into coding of bitter taste information in the peripheral taste system.