title: Effects of gamma-aminobutyric acid and (-)-baclofen on calcium and potassium currents in cat dorsal root ganglion neurones in vitro.
abstract: Calcium and potassium currents were examined in dialysed, isolated dorsal root ganglion neurones of the cat by use of a single electrode voltage clamp. Two calcium currents were identified, a low threshold inactivating (transient) current and a higher threshold slowly inactivating (sustained) current. Both currents were blocked by 1 mM cadmium and replacement of calcium with manganese, which revealed an underlying nonspecific outward current. The sustained current disappeared with internal dialysis over a period of 20 to 30 min. (-)-Baclofen (100 microM) and gamma-aminobutyric acid (GABA, 100 microM) were found to reduce the peak amplitude of the sustained calcium current, an effect which became more pronounced with increasing concentrations of external magnesium (1-5 mM). In 5 mM external magnesium, 100 microM baclofen reduced the calcium current by 28%. The voltage-activated delayed rectifier appeared to be the most prominent potassium current in these cells. We were unable to find any evidence for a significant contribution from calcium-activated potassium conductance or a transient potassium conductance under our recording conditions. Baclofen and GABA at 100 microM had no consistent effect on the voltage-activated potassium current. Baclofen did not change the resting potassium conductance.
mesh_terms: D000818:Animals; D001418:Baclofen / Q000494:pharmacology*; D002415:Cats; D004566:Electrodes; D005727:Ganglia, Spinal / Q000187:drug effects; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D007473:Ion Channels; D005680:gamma-Aminobutyric Acid; D001418:Baclofen