T-type calcium channels consolidate tonic action potential output of thalamic neurons to neocortex

• Published in: The Journal of neuroscience Vol. 32; no. 35; pp. 12228 - 12236
• Main Authors: Deleuze, Charlotte, David, François, Béhuret, Sébastien, Sadoc, Gérard, Shin, Hee-Sup, Uebele, Victor N, Renger, John J, Lambert, Régis C, Leresche, Nathalie, Bal, Thierry
• Format: Journal Article
• Language: English
• Published: United States Society for Neuroscience 29.08.2012
• Subjects: Action Potentials; Action Potentials - physiology; Animals; Calcium Channels, T-Type; Calcium Channels, T-Type - physiology; Female; Life Sciences; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Models, Neurological; Neocortex; Neocortex - cytology; Neocortex - physiology; Neurons; Neurons - physiology; Neurons and Cognition; Thalamus; Thalamus - cytology; Thalamus - physiology; Wakefulness; Wakefulness - physiology
• ISSN: 0270-6474; 1529-2401; 1529-2401
• DOI: 10.1523/JNEUROSCI.1362-12.2012

The thalamic output during different behavioral states is strictly controlled by the firing modes of thalamocortical neurons. During sleep, their hyperpolarized membrane potential allows activation of the T-type calcium channels, promoting rhythmic high-frequency burst firing that reduces sensory information transfer. In contrast, in the waking state thalamic neurons mostly exhibit action potentials at low frequency (i.e., tonic firing), enabling the reliable transfer of incoming sensory inputs to cortex. Because of their nearly complete inactivation at the depolarized potentials that are experienced during the wake state, T-channels are not believed to modulate tonic action potential discharges. Here, we demonstrate using mice brain slices that activation of T-channels in thalamocortical neurons maintained in the depolarized/wake-like state is critical for the reliable expression of tonic firing, securing their excitability over changes in membrane potential that occur in the depolarized state. Our results establish a novel mechanism for the integration of sensory information by thalamocortical neurons and point to an unexpected role for T-channels in the early stage of information processing.