Membrane properties of isolated mudpuppy taste cells.
The voltage-dependent currents of isolated Necturus lingual cells were studied using the whole-cell configuration of the patch-clamp technique. Nongustatory surface epithelial cells had only passive membrane properties. Small, spherical cells resembling basal cells responded to depolarizing voltage steps with predominantly outward K+ currents. Taste receptor cells generated both outward and inward currents in response to depolarizing voltage steps. Outward K+ currents activated at approximately 0 mV and increased almost linearly with increasing depolarization. The K+ current did not inactivate and was partially Ca++ dependent. One inward current activated at -40 mV, reached a peak at -20 mV, and rapidly inactivated. This transient inward current was blocked by tetrodotoxin (TTX), which indicates that it is an Na+ current. The other inward current activated at 0 mV, peaked at 30 mV, and slowly inactivated. This more sustained inward current had the kinetic and pharmacological properties of a slow Ca++ current. In addition, most taste cells had inwardly rectifying K+ currents. Sour taste stimuli (weak acids) decreased outward K+ currents and slightly reduced inward currents; bitter taste stimuli (quinine) reduced inward currents to a greater extent than outward currents. It is concluded that sour and bitter taste stimuli produce depolarizing receptor potentials, at least in part, by reducing the voltage-dependent K+ conductance.
Kinnamon
S C
SC
Department of Anatomy and Neurobiology, Colorado State University, Fort Collins 80523.
Roper
S D
SD
D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004553:Electric Conductivity; D066298:In Vitro Techniques; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials; D009337:Necturus / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013649:Taste / Q000502:physiology; D013650:Taste Buds / Q000378:metabolism*
D007473:Ion Channels; D012964:Sodium; D011188:Potassium; D002118:Calcium