Unité de Neurosciences, Information et Complexité (UNIC), UPR 3293 CNRS, 91198 Gif-sur-Yvette, France.
J Neurosci. 2012 Aug 29;32(35):12228-36. 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.
在不同的行为状态下，丘脑的输出受到丘脑皮质神经元放电模式的严格控制。在睡眠期间，它们的超极化膜电位允许 T 型钙通道的激活，促进节律性高频爆发式放电，从而减少感觉信息传递。相比之下，在清醒状态下，丘脑神经元主要以低频（即紧张性放电）产生动作电位，使传入的感觉输入能够可靠地传递到皮质。由于 T 型通道在清醒状态下经历的去极化电位中几乎完全失活，因此人们认为它们不会调节紧张性动作电位的放电。在这里，我们使用小鼠脑片证明，在去极化/类似清醒状态下维持的丘脑皮质神经元中 T 型通道的激活对于紧张性放电的可靠表达至关重要，确保了它们在去极化状态下发生的膜电位变化中的兴奋性。我们的结果为丘脑皮质神经元整合感觉信息建立了一种新的机制，并指出 T 型通道在信息处理的早期阶段具有意想不到的作用。
