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Chloride distribution in Aplysia neurones
Author(s) -
Ascher P.,
Kunze Diana,
Neild T. O.
Publication year - 1976
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1976.sp011332
Subject(s) - aplysia , chemistry , conductance , tetraethylammonium , intracellular , biophysics , depolarization , resting potential , membrane potential , ion , chloride , potassium , biochemistry , biology , neuroscience , mathematics , organic chemistry , combinatorics
1. The intracellular Cl − concentration (Cl i ) and the membrane potential ( E m ) were measured in the medial pleural neurones of Aplysia under various experimental conditions designed to determine the Cl − conductance of the neurones and investigate the possibility of an active Cl − transport. 2. The magnitude of the Cl − conductance of the cell depends on the experimental conditions. 3. In normal sea water, large changes of E m produced by passing current across the cell membrane caused no change of Cl i , suggesting that the Cl − conductance was low. Similarly, moderate changes of E Cl produced by decreasing Cl o or increasing Cl i had little or no effect on E m . 4. A high Cl − conductance was observed in high K o or very low Cl o . It was greatly reduced if the external Ca 2+ was replaced by Co 2+ , or in the presence of tubocurarine, or if the experiment was performed on an isolated cell soma. The high Cl − conductance is therefore attributed to the release of ACh and perhaps other transmitters from synaptic terminals. 5. High concentrations of tetraethylammonium ions or procaine induced a depolarization of the cell, but a decrease of Cl i . The rate of fall of Cl i was increased by lowering external K + or raising external Ca 2+ , and was decreased by replacing external Ca 2+ by Co 2+ . 6. NH 4 + ions applied externally had effects similar to those of K + ions. In situations in which intracellular NH 4 + might be increased a fall in Cl i was observed. 7. The changes of Cl i caused by TEA, procaine, or internal NH 4 + occur against the driving force for passive Cl − movements. They are still observed in isolated cell bodies, and cannot be attributed to the activation of synaptic channels. 8. Some interpretations of these anomalous Cl − movements are discussed which could also account for the difference between E Cl and E m observed under normal conditions.