Hyperpolarization-Activated Current (Ih) in the Inferior Colliculus: Distribution and Contribution to Temporal Processing

Neurons in the inferior colliculus exhibit varying amplitudes of the hyperpolarization-activated current (Ih), with largest amplitudes found in onset neurons.

• Three basic response types were identified in IC neurons: onset, adapting, and sustained.
• Onset and adapting neurons displayed an Ih-dependent depolarizing sag, a more depolarized resting membrane potential, and lower input resistance compared to sustained neurons.
• Ih amplitudes were largest in onset neurons, medium in adapting neurons, and small in sustained neurons.
• The activation kinetics of Ih were voltage dependent and faster in onset and adapting neurons than in sustained neurons.
• Ih reduced temporal summation of excitatory and inhibitory potentials in onset neurons but not in sustained neurons.
• Blocking Ih abolished afterhyperpolarization and rebound spiking in the neurons.

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