Block by the neuropeptide TRH of an apparently novel K+ conductance of rat motoneurones.
Using a single electrode voltage clamp technique the actions of rapidly superfused thyrotropin-releasing hormone (TRH, 1 microM) on lumbar motoneurones of the isolated neonatal rat spinal cord were investigated. TRH induced a slowly developing inward current (associated with an input conductance fall) with slow recovery on washout. In the presence of TRH the normally linear current-voltage relations displayed strong inward rectification up to about -40 mV. The TRH-induced current peaked at -50 mV, reversed at -120 mV and was not blocked by Cs+, tetraethylammonium, 4-aminopyridine, Cd2+, or low Na+. Its reversal potential was sensitive to changes in extracellular K+. Ba2+ (0.2-1.5 mM) depressed the effects of TRH. It is suggested that in rat motoneurones TRH blocked an apparently novel K+ conductance (IK(T)) active at resting membrane potential.
Nistri
A
A
Department of Pharmacology, St. Bartholomew's Hospital Medical College, University of London, U.K.
Fisher
N D
ND
Gurnell
M
M
D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D013116:Spinal Cord / Q000502:physiology*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D013973:Thyrotropin-Releasing Hormone; D019789:Tetraethylammonium; D015761:4-Aminopyridine