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Serotonin modulates spike probability in the axon initial segment through HCN channels
Kwang Woo Ko1,2, Matthew N Rasband3, Victor Meseguer4
1Department of Neuroscience, University of Texas at Austin, Austin, Texas, USA.
Nature Neuroscience
|April 26, 2016
Summary
Hyperpolarization and cyclic-nucleotide-gated (HCN) channels in the axon initial segment (AIS) regulate neuronal excitability. Serotonin modulates these axonal HCN channels, influencing sensory processing during attention and motivation shifts.
Area of Science:
- Neuroscience
- Cellular Neuroscience
- Ion Channel Physiology
Background:
- The axon initial segment (AIS) is critical for action potential initiation.
- Isolating AIS function from somatic and dendritic effects has been challenging.
- Understanding AIS ion channel contributions to neural coding is incomplete.
Purpose of the Study:
- To investigate the role and regulation of hyperpolarization and cyclic-nucleotide-gated (HCN) channels in the AIS.
- To determine how AIS HCN channels influence neuronal excitability and spike probability.
- To explore the impact of serotonergic modulation on AIS HCN channel function.
Main Methods:
- Confocal microscopy and patch-clamp recordings in gerbil auditory neurons.
- Utilized light-sensitive channel blockers (photoswitches) to isolate AIS effects.
- Investigated the effects of 5-hydroxytryptamine 1A (5-HT1A) receptor modulation.
Main Results:
- HCN channels are expressed in the AIS and reduce spike probability, distinct from somatic/dendritic HCN channels.
- AIS HCN channel function, controlling spike threshold, is modulated by serotonin via 5-HT1A receptors.
- Serotonergic modulation shifts the activation range of HCN channels, altering neuronal excitability.
Conclusions:
- Axonal HCN channels are key regulators of neuronal excitability at the AIS.
- Serotonergic signaling through 5-HT1A receptors provides a mechanism to tune neuronal responses.
- This pathway links neuromodulatory states (attention, motivation) to sensory processing thresholds.
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