Ttypekanaler

T-typekanaler, or T-type calcium channels, are a family of voltage-gated calcium channels that activate at relatively low membrane potentials and inactivate rapidly. They belong to the Cav3 family of low-threshold, transient calcium channels and are encoded by three main genes: CACNA1G (Cav3.1), CACNA1H (Cav3.2), and CACNA1I (Cav3.3). The alpha1 subunits form the pore of the channel and determine its voltage dependence and kinetics, while auxiliary subunits modulate expression and function.

These channels produce small, transient calcium currents that open during small depolarizations, typically from around −60 to −40 mV. They recover quickly from inactivation and can respond to repetitive activity, contributing to subthreshold excitability and calcium signaling in neurons and other cell types. The currents are relatively small compared with high-threshold calcium channels but have outsized effects on firing patterns because they generate low-threshold spikes that can trigger bursts of action potentials.

Distribution and function: T-type channels are especially important in brain regions such as the thalamus, where they underlie low-threshold calcium spikes that promote burst firing and thalamocortical oscillations involved in sleep rhythms. They are also present in other parts of the nervous system, including sensory pathways, and in some cardiac tissues during development. Functionally, they influence neuronal excitability, rhythmic activity, and pacemaking in certain cells.

Pharmacology and clinical relevance: Ethosuximide, a drug used to treat absence seizures, acts in part by inhibiting T-type currents. Other selective or non-selective T-type channel inhibitors have been explored in research settings. Aberrant T-type channel activity has been implicated in neurological conditions such as absence epilepsy and certain pain states, making these channels a target of ongoing therapeutic research.