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Inhibition of calcium currents in cultured rat dorsal root ganglion neurones by (−)‐baclofen
Author(s) -
Dolphin A.C.,
Scott R.H.
Publication year - 1986
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.1476-5381.1986.tb09489.x
Subject(s) - baclofen , dorsal root ganglion , calcium , dorsum , ganglion , neuroscience , chemistry , anatomy , pharmacology , medicine , biology , agonist , biochemistry , receptor
1 Voltage‐dependent inward calcium currents (I Ca ) activated in cultured rat dorsal root ganglion neurones were reversibly reduced in a dose‐dependent manner by (−)‐baclofen (10 μM to 100 μM). 2 Baclofen (100 μM) reduced the calcium‐dependent slow outward potassium current (I K(Ca) ). This current was abolished in calcium‐free medium and by 300 μM cadmium chloride. The action of baclofen on I K(Ca) was reduced when the calcium concentration in the medium was increased from 5 mM to 30 mM. 3 The calcium independent fast transient voltage‐dependent outward current (I K(Vt) ) was also reduced by baclofen; this effect remained present when Ca 2+ ‐free medium was used to prevent contamination by I K(Ca) . 4 4‐Aminopyridine (500 μM) reduced I K(Vt) and induced a small increase in I Ca . The action of baclofen on I Ca was partially antagonized by 4‐aminopyridine. 5 GABA B receptor‐mediated inhibition of I Ca in cultured rat dorsal root ganglion neurones involves a direct mechanism rather than resulting indirectly from an increase in the residual outward potassium currents activated by depolarization. The reduction in I Ca by baclofen was variable and dependent on the amplitude of control I Ca , larger currents being more resistant to the baclofen‐induced inhibition.