Department of Anesthesiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA.
Anesthesiology. 2010 Dec;113(6):1299-309. doi: 10.1097/ALN.0b013e3181f90ccc.
Temporary, antegrade amnesia is one of the core desirable endpoints of general anesthesia. Multiple lines of evidence support a role for the hippocampal θ rhythm, a synchronized rhythmic oscillation of field potentials at 4-12 Hz, in memory formation. Previous studies have revealed a disruption of the θ rhythm at surgical levels of anesthesia. We hypothesized that θ-rhythm modulation would also occur at subhypnotic but amnestic concentrations. Therefore, we examined the effect of three inhaled agents on properties of the θ rhythm considered critical for the formation of hippocampus-dependent memories.
We studied the effects of halothane and nitrous oxide, two agents known to modulate different molecular targets (GABAergic [γ-aminobutyric acid] vs. non-GABAergic, respectively) and isoflurane (GABAergic and non-GABAergic targets) on fear-conditioned learning and θ oscillations in freely behaving rats.
All three anesthetics slowed θ peak frequency in proportion to their inhibition of fear conditioning (by 1, 0.7, and 0.5 Hz for 0.32% isoflurane, 60% N2O, and 0.24% halothane, respectively). Anesthetics inconsistently affected other characteristics of θ oscillations.
At subhypnotic amnestic concentrations, θ-oscillation frequency was the parameter most consistently affected by these three anesthetics. These results are consistent with the hypothesis that modulation of the θ rhythm contributes to anesthetic-induced amnesia.
暂时的顺行性遗忘是全身麻醉的核心期望终点之一。多条证据表明海马θ节律（场电位以 4-12 Hz 的同步节律性振荡）在记忆形成中起作用。先前的研究表明，在手术麻醉水平，θ 节律会中断。我们假设，在催眠但健忘的浓度下，θ 节律也会发生调制。因此，我们研究了三种吸入性麻醉剂对被认为对海马依赖性记忆形成至关重要的θ 节律特性的影响。
我们研究了氟烷和一氧化二氮（分别调节不同的分子靶点：GABA 能[γ-氨基丁酸]与非 GABA 能）和异氟醚（GABA 能和非 GABA 能靶点）对自由行为大鼠恐惧条件学习和θ 振荡的影响。
所有三种麻醉剂均使θ 波峰频率按其对恐惧条件反射的抑制作用（分别为 0.32%异氟醚、60%氧化亚氮和 0.24%氟烷时，θ 波峰频率分别降低 1、0.7 和 0.5 Hz）的比例减慢。麻醉剂对其他θ 振荡特性的影响不一致。
在催眠健忘浓度下，这些三种麻醉剂最一致地影响θ 振荡频率。这些结果与以下假设一致，即θ 节律的调制有助于麻醉诱导的遗忘。
