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Voltage‐clamp analysis of a self‐inhibitory synaptic potential in the buccal ganglia of Aplysia.
Author(s) -
Gardner D
Publication year - 1977
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.1977.sp011701
Subject(s) - aplysia , curare , inhibitory postsynaptic potential , biophysics , resting potential , chemistry , voltage clamp , hyperpolarization (physics) , reversal potential , electrophysiology , neuroscience , membrane potential , conductance , postsynaptic potential , patch clamp , physics , biology , stereochemistry , receptor , biochemistry , condensed matter physics , nuclear magnetic resonance spectroscopy
1. In cholinergic neurones BL4, BL5, BR4, and BR5 of Aplysia buccal ganglia, each action potential is followed, in the same cell, by a curare‐ and high‐Mg‐sensitive hyperpolarizing after‐potential which is enhanced by Ca. 2. In voltage‐clamped neurons, substracting currents recorded in curare from currents recorded in sea water reveals that this potential is due to curare‐sensitive currents which rise to a peak, then decay exponentially with an apparently voltage‐independent time constant of 43 msec. Currents are produced by a voltage‐independent, Ca‐enhanced, conductance change with a 0‐26 mumho peak and a ‐64 mV reversal potential. The curare‐sensitive conductance is also sensitive to high Mg. 3. Both after‐potential and curare‐ or Mg‐sensitive current follow each action potential without failures, even in threshold‐raising 80 mM‐Ca‐144‐mM‐Mg solutions. 4. Both after‐potential and current decrease with repetitive firing or short inter‐spike interval, possibly due to receptor desensitization. 5. The Mg‐ and curare‐sensitive conductance is also blocked by 1 mM‐ACh. 6. The data are consistent with the hypothesis that the hyperpolarization following action potentials in each of these four neurones is produced by a self‐inhibitory synaptic mechanism.