Cochran SL.
Abstr Soc Neurosci. 1990; 16: 968.
Dept. Life Sciences, Indiana State Univ., Terre Haute 47809.
This study is directed towards understanding how ions are involved in transmission between hair cells and afferent fibers in the isolated vestibular labyrinth of the frog, Rana pipiens. Intracellular recordings from lagena and canal afferents are digitized at 50 KHz for several minutes. EPSPs (several thousand per cell) are detected by computer algorithm and their frequency of occurrence and amplitudes are quantified. Increasing the Na+ concentration of the solution bathing the tissue by 10-50 mM results in an increase in the mean amplitude of the EPSPs (19 cells), suggesting that the hair cell transmitter opens subsynaptic Na+ channels. Reducing the Ca+2 concentration from 2 to 0.125 mM results in an increase in EPSP amplitude (22 cells), while increasing the Ca+2 concentration to 4 or 8 mM results in a decrease in amplitude and frequency (17 cells), suggesting that Ca+2 may to some extent block the subsynaptic Na+ channel. Increasing the K+ concentration from 2 to 5 mM results in a 100 fold increase in the EPSP frequency with no change in amplitude (24 cells), while lowering the K+ concentration to 0 mM decreases release (4 cells), confirming that the hair cell release process is affected by presumed small changes in its membrane potential. These findings suggest that the subsynaptic channel may resemble that found at the neuromuscular junction and indicate that this neuropil is very sensitive to small changes in ionic concentrations.
Publication Types:
Keywords:
- Animals
- Anura
- Calcium
- Calcium Signaling
- Ear, Inner
- Excitatory Postsynaptic Potentials
- Hair Cells, Auditory
- Membrane Potentials
- Neuromuscular Junction
- Potassium
- Rana pipiens
- Ranidae
- Sodium
- Synapses
- transmission
- NASA Discipline Neuroscience
- NASA Discipline Number 16-20
- NASA Program Space Biology
- Non-NASA Center
Other ID:
UI: 102212898
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