The enigmatic HCN channels: A cellular neurophysiology perspective

Area of Science:

• Neuroscience
• Cellular Physiology
• Ion Channel Function

Background:

• Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels possess mixed cation selectivity and unique gating kinetics.
• These channels are widely expressed in neurons, playing a role in neuronal excitability.
• Their precise physiological function in the context of fast neuronal signaling remained a puzzle.

Purpose of the Study:

• To review the physiological roles of HCN channels in neuronal function.
• To emphasize assessing HCN channels' response to time-varying signals and their interactions with other cellular components.
• To explore the implications of HCN channel distribution and plasticity.

Main Methods:

• Review of existing literature on HCN channel structure, function, and physiological roles.
• Analysis of HCN channel contributions to neuronal response characteristics.
• Discussion of HCN channel interactions with other ion channels and receptors.
• Exploration of HCN channel subcellular distribution and plasticity.

Main Results:

• HCN channels mediate a slow negative feedback loop influencing neuronal gain, voltage sag, rebound, temporal summation, resonance, and coincidence detection.
• Interactions with other channels enable HCN channels to regulate intrinsic oscillations, spike frequency adaptation, and neurotransmitter release.
• Spatially non-homogeneous distributions and plasticity of HCN channels contribute to diverse encoding, homeostatic, and neuroprotective functions.

Conclusions:

• HCN channels are crucial regulators of neuronal excitability and function through unique gating kinetics and interactions.
• Their roles extend from shaping individual action potentials to influencing network-level phenomena.
• Understanding HCN channel dynamics is key to comprehending neuronal computation and adaptation.