Electrophysiologically identified subpopulations of taste bud cells

The heterogeneous population of mammalian taste cells includes several cellular subtypes specializing in distinct physiological functions. They are poorly understood at the single cell level because the available physiological data have generally been obtained from unidentified taste cells. We recorded them from individual taste cells isolated from circumvallate, foliate, and fungiform papilla of the mouse, employing the patch clamp technique, and tried to elucidate whether universal electrophysiological criteria may be established for the identification of functionally different cellular subpopulations. It was found that irrespective of the papillae type, most ( approximately 96%) of robust taste cells could be categorized into three distinct subgroups on the basis of families of whole-cell (WC) currents exhibited in response to membrane polarization. The validity of this quite simple criterion was further confirmed by using different voltage clamp protocols, ion substitutions, and channel blockers to record different ionic currents, including voltage-gated (VG) Ca(2+), inward-rectifying K(+), and hyperpolarization-activated currents. Given that our findings are based on the statistically significant number of recordings, we believe that the electrophysiological identification of taste cells presented here may be effective for further studies on single taste cell physiology, including taste transduction.