title: Supporting-cell and extracellular responses to acoustic clicks in the free-standing region of the alligator lizard cochlea.
abstract: 1. Acoustic clocks were delivered to the tympanic membrane of anesthetized alligator lizards, and electric responses were measured within the free-standing region of the cochlea using glass micropipettes. Responses were recorded intracellularly in supporting cells and extracellularly in the receptor organ and in the scalae. Gross responses were also recorded with wire electrodes in scala tympani. 2. Intra- and extracellular responses contain two components: (1) an early (with latent period less than 0.15 ms after the onset of the click), rate-independent component presumed to originate in the receptor cells, which we call the 'receptor component'; and (2) a later (with latent period from 2 to 5 ms after the onset of the click), rate-dependent component presumed to originate in the primary neurons, which we call the 'neural component'. 3. The receptor component consists of a positive, slow, polarity-independent potential which is superimposed on a small, oscillatory, polarity-dependent potential. The average magnitude of the receptor component in supporting cells (0.72 mV for -20 dB clicks) is about 10 times that in the extracellular spaces and about 1/5 of that recorded in receptor cells. This component depends nonlinearly on the sound stimulus in the -20 to -55 dB range of click levels. 4. The average magnitude of the neural component in supporting cells (0.3 mV for clicks at -20 dB and 10 clicks/s) is about 5-10 times larger than that in the extracellular spaces. 5. The receptor and neural components have different distributions within the cochlea. The slow potential of the receptor component has positive polarity within the receptor organ and in scala tympani, and negative polarity in scala media. In contrast, the neural component has approximately the same biphasic (negative then positive) waveform in all extracellular compartments where it was detected. However, the neural component has a larger magnitude and an inverted (positive then negative) waveform in supporting cells. The neural component has not been detected in receptor cells.
mesh_terms: D000161:Acoustic Stimulation; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D003051:Cochlea / Q000502:physiology*; D003055:Cochlear Microphonic Potentials; D006198:Hair Cells, Auditory / Q000502:physiology; D007760:Labyrinth Supporting Cells / Q000502:physiology; D008116:Lizards / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D011930:Reaction Time; D012533:Scala Tympani / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D013779:Tetrodotoxin