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Voltage‐dependent drug blockade of L‐glutamate activated channels of the crayfish.
Author(s) -
Dekin M S,
Edwards C
Publication year - 1983
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.1983.sp014796
Subject(s) - glutamate receptor , acetylcholine , excitatory postsynaptic potential , neuromuscular junction , biophysics , reversal potential , chemistry , membrane potential , neuroscience , biology , electrophysiology , pharmacology , biochemistry , patch clamp , receptor
The actions of d‐tubocurarine (d‐TC) and local anaesthetics on the L‐glutamate activated channel at the voltage‐clamped crayfish neuromuscular junction were studied. The effect of d‐TC and local anaesthetics on the dose‐response relationship between ionophoretically applied L‐glutamate and synaptic current suggested that both acted as non‐competitive inhibitors. The amount of inhibition was voltage dependent, and increased as the membrane potential was hyperpolarized. This voltage‐dependent block was also manifest in a flattening of the I‐V relationship between L‐glutamate induced current and membrane potential in the presence of d‐TC. However, the reversal potential for the L‐glutamate activated channel was not affected; it was about +7 mV in both the presence and absence of d‐TC. The neurally evoked excitatory post‐synaptic current (e.p.s.c.) was depressed in the presence of these drugs and this effect was also voltage dependent. The time course of the e.p.s.c. was affected, but less so than expected if the L‐glutamate activated channel were identical to the channel opened by acetylcholine at the vertebrate neuromuscular junction. Possible reasons for this discrepancy are discussed.