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Effects of iontophoretically applied drugs on spinal interneurones of the lamprey
Author(s) -
Martin A. R.,
Wickelgren Warren O.,
Berànek R.
Publication year - 1970
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.1970.sp009086
Subject(s) - membrane potential , inhibitory postsynaptic potential , iontophoresis , depolarization , reversal potential , hyperpolarization (physics) , biophysics , resting potential , chemistry , lamprey , acetylcholine , electrophysiology , glutamate receptor , neuroscience , spinal cord , biology , patch clamp , pharmacology , biochemistry , stereochemistry , fishery , nuclear magnetic resonance spectroscopy , receptor
1. Intracellular records were obtained from giant interneurones in the isolated spinal cord of the sea lamprey. The cells had a mean resting potential of about 75 mV and action potentials with overshoots of about 35 mV. Their input resistances, measured by passing polarizing currents through the recording pipette, were in the range 3‐7 MΩ. 2. Iontophoretic ejection of γ‐aminobutyric acid (GABA) from a micropipette placed near the surface of a cell resulted in a slight hyperpolarization, accompanied by a marked reduction in input resistance. The reversal point for the potential change was about 5 mV greater than the resting membrane potential. 3. Iontophoretic application of L ‐glutamate to the cells produced a depolarization with a decrease in input resistance much smaller than that accompanying a GABA potential of similar amplitude. The action potential amplitude was reduced by L ‐glutamate application. The reversal potential could not be determined accurately but appeared to be near zero membrane potential. 4. Glutamate application produced, in addition, a burst of inhibitory synaptic potentials in the cell, presumably by depolarizing either inhibitory presynaptic nerve terminals or nearby inhibitory cell bodies. 5. Acetylcholine (ACh) produced no detectable change in membrane resistance or potential. 6. Application of the three drugs to first‐order sensory cells in the spinal cord had no effect on their membrane properties.