hyperpolarization-activated current
An inward current activated by membrane hyperpolarization, mediated by HCN channels and important for pacemaking and rhythmic activity.
Full Definition
Hyperpolarization-activated current (Ih) is a unique inward current that is activated by membrane hyperpolarization rather than depolarization. It is mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and carries both sodium and potassium ions. Ih plays crucial roles in determining resting potential, input resistance, and temporal integration of synaptic inputs. It is particularly important for pacemaking activity in cardiac and neural tissues, contributing to rhythmic oscillations in thalamic neurons and hippocampal interneurons. The current shows slow activation kinetics and can be modulated by cyclic nucleotides.
Usage
Usage note: Often abbreviated as Ih in electrophysiology literature.
In Context
- "The hyperpolarization-activated current contributed to the rebound firing observed after inhibitory input." — Electrophysiology study
- "Blocking the hyperpolarization-activated current with ZD7288 eliminated theta oscillations in hippocampal slices." — Pharmacology experiment