Isoflurane induces dose-dependent changes of thalamic somatosensory information transfer
Isoflurane induces dose-dependent changes of thalamic somatosensory information transfer
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DOI：
10.1016/s0006-8993(99)01341-4
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发表时间：
1999-05-22
期刊：
影响因子：
2.9
通讯作者：
Bromm, B
中科院分区：
文献类型：
--
作者：
Detsch, O;Vahle-Hinz, C;Bromm, B
尽管有一些关于挥发性麻醉剂对躯体感觉的抑制作用的报道，但其神经机制大多尚不清楚。本研究通过记录大鼠对体表机械刺激的神经反应，研究了不同浓度异氟醚作用下大鼠丘脑水平的躯体感觉冲动传递。在腹后内侧核记录丘脑皮质中继神经元(TCNs，三级神经元，n=28)和三叉神经-丘脑纤维(TTF，二级神经元，n=7)。在明确的触觉刺激(鼻窦毛发或皮毛的梯形或振动偏转)施加到神经元感受区后，对功能反应特征进行量化。呼气末异氟醚浓度在0.6%(基线)至2.0%之间以0.2%的步长递增。所有研究的TCNs的反应活性都受到剂量依赖性的抑制(2.0%异氟醚使反应降低到基线的3.5+/-1.1%；平均+/-S.E.M.)；TTFS的反应活性受到的影响要小得多(下降到55.0+/-8.2%)。然而，对于TCN和TTF，对正在进行的活动的抑制是相似的。此外，在TCNs中，在1.0%至1.8%的范围内，随着异氟醚浓度的增加，反应特性发生变化：紧张性和持续性反应转变为相性反应。相反，即使在较高的异氟醚浓度下，TTF的紧张性和持续性反应特征也得到保留。结果表明，异氟醚减弱了大鼠丘脑特定核团的体感信号输出，而其输入仅受轻微影响。观察到的丘脑神经元反应特征的改变，至少部分地可能导致在全麻期间观察到的感觉辨别能力的丧失。(C)1999 Elsevier Science B.V.保留所有权利。
In spite of several reports about suppressive effects of volatile anesthetics on somatosensation, their neuronal mechanisms are largely unknown. The present study investigates somatosensory impulse transmission at the thalamic level in rats under varied concentrations of isoflurane by recordings of neuronal responses to mechanical stimulation of the body surface. Single-unit recordings of thalamo-cortical relay neurons (TCNs, third order neurons; n = 28) and presumed trigemino-thalamic fibers (TTFs, second order neurons; n = 7) were performed in the ventral posteromedial nucleus. Functional response characteristics were quantified following defined tactile stimulation (trapezoidal or vibratory deflection of sinus hairs or fur) applied to the neuronal receptive fields. End-tidal isoflurane concentration was increased in steps of 0.2% between 0.6% (baseline) and 2.0%. The response activity in all TCNs studied was suppressed in a dose-dependent manner (2.0% isoflurane decreased responses to 3.5 +/- 1.1% of baseline; mean +/- S.E.M.); the response activity in TTFs was much less affected (decrease to 55.0 +/- 8.2%). Suppression of ongoing activity, however, was similar for both, TCNs and TTFs. Furthermore, in TCNs, the response characteristics changed with increasing isoflurane between 1.0% and 1.8%: tonic and sustained responses were converted to phasic on-responses. In contrast, the tonic and sustained response characteristics of TTFs were preserved even at higher isoflurane concentrations. The results indicate that isoflurane attenuates the output of somatosensory signals in the specific nucleus of the rat's thalamus, while its input is only marginally affected. The observed changes of thalamic neuronal response characteristics, at least in part, may cause the loss in sensory discrimination observed during general anesthesia. (C) 1999 Elsevier Science B.V. All rights reserved.