Department of Anesthesiology, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA.
Department of Anesthesiology, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA; Neuroscience and Pharmacology Graduate Program, University of Colorado, Anschutz Medical Campus, Aurora, CO, USA.
Br J Anaesth. 2021 Jan;126(1):245-255. doi: 10.1016/j.bja.2020.07.022. Epub 2020 Aug 25.
The mechanisms underlying the role of T-type calcium channels (T-channels) in thalamocortical excitability and oscillations in vivo during neurosteroid-induced hypnosis are largely unknown.
We used patch-clamp electrophysiological recordings from acute brain slices ex vivo, recordings of local field potentials (LFPs) from the central medial thalamic nucleus in vivo, and wild-type (WT) and Ca3.1 knock-out mice to investigate the molecular mechanisms of hypnosis induced by the neurosteroid analogue (3β,5β,17β)-3-hydroxyandrostane-17-carbonitrile (3β-OH).
Patch-clamp recordings showed that 3β-OH inhibited isolated T-currents but had no effect on phasic or tonic γ-aminobutyric acid A currents. Also in acute brain slices, 3β-OH inhibited the spike firing mode more profoundly in WT than in Ca3.1 knockout mice. Furthermore, 3β-OH significantly hyperpolarised neurones, reduced the amplitudes of low threshold spikes, and diminished rebound burst firing only in WT mice. We found that 80 mg kg i.p. injections of 3β-OH induced hypnosis in >60% of WT mice but failed to induce hypnosis in the majority of mutant mice. A subhypnotic dose of 3β-OH (20 mg kg i.p.) accelerated induction of hypnosis by isoflurane only in WT mice, but had similar effects on the maintenance of isoflurane-induced hypnosis in both WT and Ca3.1 knockout mice. In vivo recordings of LFPs showed that a hypnotic dose of 3β-OH increased δ, θ, α, and β oscillations in WT mice in comparison with Ca3.1 knock-out mice.
The Ca3.1 T-channel isoform is critical for diminished thalamocortical excitability and oscillations that underlie neurosteroid-induced hypnosis.
在神经甾体诱导催眠期间，T 型钙通道（T 型通道）在活体中的丘脑皮质兴奋性和振荡中的作用机制在很大程度上尚不清楚。
我们使用急性脑切片的膜片钳电生理记录、活体中央中脑核的局部场电位（LFP）记录以及野生型（WT）和 Ca3.1 敲除小鼠，研究神经甾体类似物（3β,5β,17β）-3-羟基雄甾烷-17-腈（3β-OH）诱导催眠的分子机制。
膜片钳记录显示，3β-OH 抑制分离的 T 电流，但对相或紧张型 γ-氨基丁酸 A 电流没有影响。此外，在急性脑切片中，3β-OH 在 WT 小鼠中比 Ca3.1 敲除小鼠更显著地抑制尖峰放电模式。此外，3β-OH 仅在 WT 小鼠中显著超极化神经元，降低低阈值尖峰的幅度，并减少反弹爆发放电。我们发现，80 mg kg i.p. 3β-OH 注射诱导超过 60%的 WT 小鼠进入催眠状态，但未能诱导大多数突变小鼠进入催眠状态。亚催眠剂量的 3β-OH（20 mg kg i.p.）仅在 WT 小鼠中加速异氟烷诱导的催眠，但对 WT 和 Ca3.1 敲除小鼠异氟烷诱导的催眠维持具有相似的影响。LFP 的活体记录显示，催眠剂量的 3β-OH 增加了 WT 小鼠与 Ca3.1 敲除小鼠相比，δ、θ、α 和β 振荡。
Ca3.1 T 型通道同工型对于降低神经甾体诱导催眠所必需的丘脑皮质兴奋性和振荡至关重要。
