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The response of cat spinal motoneurones to the intracellular application of agents with local anaesthetic action
Author(s) -
Engberg I.,
Flatman J.A.,
Lambert J.D.C.
Publication year - 1984
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1984.tb10763.x
Subject(s) - depolarization , hyperpolarization (physics) , iontophoresis , chemistry , membrane potential , antidromic , biophysics , microelectrode , electrophysiology , conductance , intracellular , anesthesia , neuroscience , biochemistry , stereochemistry , medicine , biology , electrode , nuclear magnetic resonance spectroscopy , mathematics , combinatorics
1 QX‐222 (the trimethyl analogue of lignocaine), methylxylocholine, lignocaine and pentobarbitone were iontophoresed intracellularly into cat lumbosacral motoneurones. Iontophoresis and recording was either from a triple‐barrelled microelectrode unit or from two separately advanced microelectrodes. 2 QX‐222 and methylxylocholine caused a very slow reversible block of the current‐evoked and antidromic action potentials (AP) with no significant change of membrane potential (E M ). Lignocaine had a minimal blocking effect on the AP. 3 No change, or only a small decrease, of membrane slope conductance (G M ) was seen when the APs had been totally abolished. 4 QX‐222 and methylxylocholine reduced the massive G m increase evoked by the passage of large depolarizing currents and converted the post‐current hyperpolarization (time constant 120–150 ms) into a depolarization of similar time course. It is suggested that the quaternary local anaesthetics can reduce the fast and slow voltage‐dependent potassium conductances. 5 Both agents totally blocked AP generation without decreasing the magnitude of the Ia e.p.s.p. 6 It is suggested that intracellularly iontophoresed QX‐222 (on account of its low lipid solubility) could be used as a pharmacological tool to block specifically the active Na and K channels in only the cell impaled by the microelectrodes.