T-type Ca²⁺ channels play an important role in many cellular processes such as hormone secretion, neurotransmitter release and cell differentiation.  

T-type channels are also known to participate in the pacemaker activities of the heart and neurons including thalamic neurons.¹ Three genes encoding T-type Ca²⁺ channels have been cloned and designated as Ca_V3.1 (CACNA1G), Ca_V3.2 (CACNA1H) and Ca_V3.3 (CACNA1I).^1-3  

While Ca_V3.1 and Ca_V3.2 are widely expressed in various tissues, Ca_V3.3 is primarily expressed in the central nervous system, where high expression has been described in thalamic neurons.  

The Ca²⁺ current generated by the Ca_V3.3 channel displays much slower activation and inactivation compared to the currents produced by Ca_V3.1 and Ca_V3.2, suggesting it might play a different role in neuronal excitability.^1,4