Developmental Changes in HCN Channel Modulation of Neocortical Layer 1 Interneurons

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Computational Neuroscience

Background:

• Layer 1 (L1) interneurons (INs) are crucial for regulating pyramidal neuron (PN) input integration and cortical network activity.
• Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels influence neuronal excitability in principal cells and some INs.
• The specific developmental roles of HCN channels in diverse L1 IN populations remain unclear.

Purpose of the Study:

• To investigate the developmental modulation of L1 INs by HCN channels in the rat medial agranular cortex (AGm).
• To identify distinct L1 IN populations and characterize their responses to HCN channel activity during development.

Main Methods:

• Electrophysiological characterization of L1 INs in the rat AGm.
• Unbiased hierarchical cluster analysis to classify IN populations.
• Assessment of developmental changes in excitability modulation by HCN channels.

Main Results:

• Three distinct IN populations were identified: regular spiking (RS), burst accommodating (BA), and non-accommodating (NA).
• Each IN group exhibited a unique developmental pattern of HCN channel-mediated excitability modulation.
• Modulation of excitatory postsynaptic potentials (EPSPs) by HCN channels increased in RS cells and decreased in NA cells throughout development, with distinct morphologies observed.

Conclusions:

• HCN channels differentially affect the excitability of distinct L1 IN populations during cortical development.
• These findings suggest a role for HCN channels in the formation and maintenance of cortical circuits by altering L1 IN excitability.
• The study highlights the importance of developmental HCN channel activity in shaping specific IN subtypes and their contribution to network function.