Abstract：
BACKGROUND: General anesthetics (eg, propofol and volatile anesthetics) enhance the slow-delta oscillations of the cortical electroencephalogram (EEG), which partly results from the enhancement of (γ-aminobutyric acid [GABA]) γ-aminobutyric acid-ergic (GABAergic) transmission. There is a GABAergic excitatory-inhibitory shift during postnatal development. Whether general anesthetics can enhance slow-delta oscillations in the immature brain has not yet been unequivocally determined.
METHODS: Perforated patch-clamp recording was used to confirm the reversal potential of GABAergic currents throughout GABAergic development in acute brain slices of neonatal rats. The power density of the electrocorticogram and the minimum alveolar concentrations (MAC) of isoflurane and/or sevoflurane were measured in P4-P21 rats. Then, the effects of bumetanide, an inhibitor of the Na + -K + -2Cl - cotransporter (NKCC1) and K + -Cl - cotransporter (KCC2) knockdown on the potency of volatile anesthetics and the power density of the EEG were determined in vivo.
RESULTS: Reversal potential of GABAergic currents were gradually hyperpolarized from P4 to P21 in cortical pyramidal neurons. Bumetanide enhanced the hypnotic effects of volatile anesthetics at P5 (for MAC LORR , isoflurane: 0.63% ± 0.07% vs 0.81% ± 0.05%, 95% confidence interval [CI], -0.257 to -0.103, P < .001; sevoflurane: 1.46% ± 0.12% vs 1.66% ± 0.09%, 95% CI, -0.319 to -0.081, P < .001); while knockdown of KCC2 weakened their hypnotic effects at P21 in rats (for MAC LORR , isoflurane: 0.58% ± 0.05% to 0.77% ± 0.20%, 95% CI, 0.013-0.357, P = .003; sevoflurane: 1.17% ± 0.04% to 1.33% ± 0.04%, 95% CI, 0.078-0.244, P < .001). For cortical EEG, slow-delta oscillations were the predominant components of the EEG spectrum in neonatal rats. Isoflurane and/or sevoflurane suppressed the power density of slow-delta oscillations rather than enhancement of it until GABAergic maturity. Enhancement of slow-delta oscillations under volatile anesthetics was simulated by preinjection of bumetanide at P5 (isoflurane: slow-delta changed ratio from -0.31 ± 0.22 to 1.57 ± 1.15, 95% CI, 0.67-3.08, P = .007; sevoflurane: slow-delta changed ratio from -0.46 ± 0.25 to 0.95 ± 0.97, 95% CI, 0.38-2.45, P = .014); and suppressed by KCC2-siRNA at P21 (isoflurane: slow-delta changed ratio from 16.13 ± 5.69 to 3.98 ± 2.35, 95% CI, -18.50 to -5.80, P = .002; sevoflurane: slow-delta changed ratio from 0.13 ± 2.82 to 3.23 ± 2.49, 95% CI, 3.02-10.79, P = .003).
CONCLUSIONS: Enhancement of cortical EEG slow-delta oscillations by volatile anesthetics may require mature GABAergic inhibitory transmission during neonatal development.
METHODS: Perforated patch-clamp recording was used to confirm the reversal potential of GABAergic currents throughout GABAergic development in acute brain slices of neonatal rats. The power density of the electrocorticogram and the minimum alveolar concentrations (MAC) of isoflurane and/or sevoflurane were measured in P4-P21 rats. Then, the effects of bumetanide, an inhibitor of the Na + -K + -2Cl - cotransporter (NKCC1) and K + -Cl - cotransporter (KCC2) knockdown on the potency of volatile anesthetics and the power density of the EEG were determined in vivo.
RESULTS: Reversal potential of GABAergic currents were gradually hyperpolarized from P4 to P21 in cortical pyramidal neurons. Bumetanide enhanced the hypnotic effects of volatile anesthetics at P5 (for MAC LORR , isoflurane: 0.63% ± 0.07% vs 0.81% ± 0.05%, 95% confidence interval [CI], -0.257 to -0.103, P < .001; sevoflurane: 1.46% ± 0.12% vs 1.66% ± 0.09%, 95% CI, -0.319 to -0.081, P < .001); while knockdown of KCC2 weakened their hypnotic effects at P21 in rats (for MAC LORR , isoflurane: 0.58% ± 0.05% to 0.77% ± 0.20%, 95% CI, 0.013-0.357, P = .003; sevoflurane: 1.17% ± 0.04% to 1.33% ± 0.04%, 95% CI, 0.078-0.244, P < .001). For cortical EEG, slow-delta oscillations were the predominant components of the EEG spectrum in neonatal rats. Isoflurane and/or sevoflurane suppressed the power density of slow-delta oscillations rather than enhancement of it until GABAergic maturity. Enhancement of slow-delta oscillations under volatile anesthetics was simulated by preinjection of bumetanide at P5 (isoflurane: slow-delta changed ratio from -0.31 ± 0.22 to 1.57 ± 1.15, 95% CI, 0.67-3.08, P = .007; sevoflurane: slow-delta changed ratio from -0.46 ± 0.25 to 0.95 ± 0.97, 95% CI, 0.38-2.45, P = .014); and suppressed by KCC2-siRNA at P21 (isoflurane: slow-delta changed ratio from 16.13 ± 5.69 to 3.98 ± 2.35, 95% CI, -18.50 to -5.80, P = .002; sevoflurane: slow-delta changed ratio from 0.13 ± 2.82 to 3.23 ± 2.49, 95% CI, 3.02-10.79, P = .003).
CONCLUSIONS: Enhancement of cortical EEG slow-delta oscillations by volatile anesthetics may require mature GABAergic inhibitory transmission during neonatal development.
摘要：
背景：全身麻醉药（例如，异丙酚和挥发性麻醉药）增强皮质脑电图（EEG）的慢δ振荡，部分原因是（γ-氨基丁酸[GABA]）γ-氨基丁酸能（GABA能）传递的增强。出生后发育过程中存在GABA能兴奋性抑制转变。尚未明确确定全身麻醉药是否可以增强未成熟大脑中的慢δ振荡。
方法：穿孔膜片钳记录用于确认新生大鼠急性脑切片中GABA能电流在整个GABA能发育过程中的逆转潜力。在P4-P21大鼠中测量了皮质电图的功率密度以及异氟烷和/或七氟醚的最低肺泡浓度（MAC）。然后，布美他尼的作用，在体内确定了Na-K-2Cl-协同转运蛋白（NKCC1）和K-Cl-协同转运蛋白（KCC2）敲低挥发性麻醉剂的效力和EEG功率密度的抑制剂。
结果：在皮质锥体神经元中，GABA能电流的逆转电位从P4到P21逐渐超极化。布美他尼在P5时增强了挥发性麻醉药的催眠作用（对于MACLORR，异氟烷：0.63%±0.07%vs0.81%±0.05%，95%置信区间[CI]，-0.257至-0.103，P<.001；七氟醚：1.46%±0.12%vs1.66%±0.09%，95％CI，-0.319至-0.081，P<.001）；而KCC2的敲减会削弱其在大鼠P21时的催眠作用（对于MACLORR，异氟烷：0.58%±0.05%至0.77%±0.20%，95%CI,0.013-0.357,P=.003;七氟醚:1.17%±0.04%至1.33%±0.04%,95%CI，0.078-0.244，P<.001）。对于皮质脑电图，慢δ振荡是新生大鼠脑电图谱的主要成分。异氟醚和/或七氟醚抑制慢δ振荡的功率密度，而不是增强，直到GABA能成熟。通过在P5处预注射布美他尼来模拟挥发性麻醉药下的慢δ振荡的增强。（异氟烷：慢δ变化比率从-0.31±0.22到1.57±1.15，95％CI，0.67-3.08，P=.007；七氟醚：慢δ变化比率从-0.46±0.25到0.95±0.97，95％K00P=0.38-23变化到2.00％变化。50
结论：挥发性麻醉药增强皮质脑电图慢δ振荡可能需要在新生儿发育过程中成熟的GABA能抑制传递。
方法：穿孔膜片钳记录用于确认新生大鼠急性脑切片中GABA能电流在整个GABA能发育过程中的逆转潜力。在P4-P21大鼠中测量了皮质电图的功率密度以及异氟烷和/或七氟醚的最低肺泡浓度（MAC）。然后，布美他尼的作用，在体内确定了Na-K-2Cl-协同转运蛋白（NKCC1）和K-Cl-协同转运蛋白（KCC2）敲低挥发性麻醉剂的效力和EEG功率密度的抑制剂。
结果：在皮质锥体神经元中，GABA能电流的逆转电位从P4到P21逐渐超极化。布美他尼在P5时增强了挥发性麻醉药的催眠作用（对于MACLORR，异氟烷：0.63%±0.07%vs0.81%±0.05%，95%置信区间[CI]，-0.257至-0.103，P<.001；七氟醚：1.46%±0.12%vs1.66%±0.09%，95％CI，-0.319至-0.081，P<.001）；而KCC2的敲减会削弱其在大鼠P21时的催眠作用（对于MACLORR，异氟烷：0.58%±0.05%至0.77%±0.20%，95%CI,0.013-0.357,P=.003;七氟醚:1.17%±0.04%至1.33%±0.04%,95%CI，0.078-0.244，P<.001）。对于皮质脑电图，慢δ振荡是新生大鼠脑电图谱的主要成分。异氟醚和/或七氟醚抑制慢δ振荡的功率密度，而不是增强，直到GABA能成熟。通过在P5处预注射布美他尼来模拟挥发性麻醉药下的慢δ振荡的增强。（异氟烷：慢δ变化比率从-0.31±0.22到1.57±1.15，95％CI，0.67-3.08，P=.007；七氟醚：慢δ变化比率从-0.46±0.25到0.95±0.97，95％K00P=0.38-23变化到2.00％变化。50
结论：挥发性麻醉药增强皮质脑电图慢δ振荡可能需要在新生儿发育过程中成熟的GABA能抑制传递。
