许多神经活性类固醇通过增强γ-氨基丁酸(GABAA)电流来诱导镇静/催眠。然而,我们先前证明了内源性神经活性类固醇表孕烷酮[(3β,5β)-3-羟基孕烷-20-酮](EpiP)发挥有效的外周镇痛作用,并阻断T型钙电流,同时保留大鼠感觉神经元的GABAA电流。这项研究旨在研究全身性给药EpiP引起的行为效应,并表征其作为常用全身麻醉药(GA)的佐剂的用途。
这里,我们利用脑电图(EEG)记录来表征丘脑皮质振荡,以及使用T通道亚型的野生型(WT)和不同敲除(KO)模型进行行为评估和小鼠遗传学,以研究EpiP的潜在镇静/催眠和固定特性。
与较慢脑电图频率的振荡增加一致,当单独腹膜内(i.p.)注射时,EpiP在WT小鼠中诱导催眠状态,并有效促进异氟烷(ISO)和七氟醚(SEVO)的麻醉作用。与WT小鼠相比,CaV3.1(Cacna1g)KO小鼠对EpiP诱导的催眠的敏感性降低,而CaV3.2(Cacna1h)之间没有显着差异,CaV3.3(Cacna1i)和WT小鼠。最后,与WT小鼠相比,EpiP诱导的催眠在CaV3.2KO小鼠中延迟,但在CaV3.1和CaV3.3KO小鼠中未延迟。
我们认为EpiP可能作为挥发性麻醉剂的新型催眠药和/或佐剂具有重要作用。我们推测EpiP在所有三种T通道同工型中的不同催眠作用是由于它们在丘脑皮层电路中的差异表达。
Many neuroactive steroids induce sedation/hypnosis by potentiating γ-aminobutyric acid (GABAA) currents. However, we previously demonstrated that an endogenous neuroactive steroid epipregnanolone [(3β,5β)-3-hydroxypregnan-20-one] (EpiP) exerts potent peripheral analgesia and blocks T-type calcium currents while sparing GABAA currents in rat sensory neurons. This study seeks to investigate the behavioral effects elicited by systemic administration of EpiP and to characterize its use as an adjuvant agent to commonly used general anesthetics (GAs).
Here, we utilized electroencephalographic (EEG) recordings to characterize thalamocortical oscillations, as well as behavioral assessment and mouse genetics with wild-type (WT) and different knockout (KO) models of T-channel isoforms to investigate potential sedative/hypnotic and immobilizing properties of EpiP.
Consistent with increased oscillations in slower EEG frequencies, EpiP induced an hypnotic state in WT mice when injected alone intra-peritoneally (i.p.) and effectively facilitated anesthetic effects of isoflurane (ISO) and sevoflurane (SEVO). The CaV3.1 (Cacna1g) KO mice demonstrated decreased sensitivity to EpiP-induced hypnosis when compared to WT mice, whereas no significant difference was noted between CaV3.2 (Cacna1h), CaV3.3 (Cacna1i) and WT mice. Finally, when compared to WT mice, onset of EpiP-induced hypnosis was delayed in CaV3.2 KO mice but not in CaV3.1 and CaV3.3 KO mice.
We posit that EpiP may have an important role as novel hypnotic and/or adjuvant to volatile anesthetic agents. We speculate that distinct hypnotic effects of EpiP across all three T-channel isoforms is due to their differential expression in thalamocortical circuitry.