A hyperpolarization-activated cation current (Ih) contributes to resting membrane potential in rat superior cervical sympathetic neurones.
Using perforated-patch voltage-clamp recording, a prominent hyperpolarization-activated inward cation current (Ih) has been identified in dissociated, cultured and replated, superior cervical sympathetic (SCG) neurones from 17-day-old rats. Ih was identified as a slowly activated inward current on hyperpolarizing from -60 mV, with an extrapolated null potential (in 3 mM [K+]out) of -42 mV. The activation range for Ih was -40 to -100 mV, with a half-activation voltage (V0.5) of -63 mV. The current was suppressed by 1 mM Cs+ but not by 1 mM Ba2+. The reversal potential for the current change induced by Cs+ agreed with the null potential for Ih. Ih conferred strong inward rectification to the current-voltage curve negative to -55 mV in both voltage-clamp and current-clamp recording. This inward rectification was reduced by 1 mM Cs+. In a sample of eight cells with initial resting membrane potentials between -51 and -64 mV, Cs+ increased the resting potential of all cells by between 2.5 and 21 mV. These results indicate that Ih contributes a tonic inward (depolarizing) component to the maintenance of the resting membrane potential in SCG neurones.
Lamas
J A
JA
Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
D000818:Animals; D002478:Cells, Cultured; D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels; D051381:Rats; D017783:Superior Cervical Ganglion / Q000166:cytology / Q000502:physiology*
D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D009419:Nerve Tissue Proteins; D015221:Potassium Channels