ELECTROPHYSIOLOGICAL CHARACTERIZATION OF A PUTATIVE SUPPORTING CELL ISOLATED FROM THE FROG TASTE DISK

Chemosensory cells in vertebrate taste organs have two obvious special izations: an apical membrane with access to the tastants occurring in food, and synapses with sensory axons. In many species, however, certa in differentiated taste cells have access to the tastants but lack any synaptic contacts with axons, and a supportive rather than chemosenso ry function has been attributed to them. Until now, no functional data are available for these taste cells. To begin to understand their rol e in taste organ physiology, we have characterized with patch-clamp re cording techniques the electrophysiological properties of a putative s upporting cell-the so-called wing cell-isolated from frog taste disks. Wing cells were distinguished from chemosensory elements by the prese nce of a typical, sheet-like apical process. Their resting potential w as approximately -52 mV, and the average input resistance was 4.8 G Om ega. Wing cells possessed voltage-gated Na+ currents sensitive to TTX, and an inactivating, voltage-gated K+ current sensitive to TEA. Curre nt injections elicited single action potentials but not repetitive fir ing. We found no evidence for voltage-gated Ca2+ currents under variou s experimental conditions. Amiloride-sensitive Na+ channels, thought t o be involved in Na+ chemotransduction, were present in wing cells. Ma ny of the membrane properties of wing cells have been also reported fo r chemosensory taste cells. The presence of ion channels in wing cells might be suggestive of a role in controlling the microenvironment ins ide the taste organs or the functioning of chemosensory cells or both. In addition, they might participate directly in the sensory transduct ion events by allowing loop currents to flow inside the taste organs d uring chemostimulation.