Harris B D, Wong G, Moody E J, Skolnick P
Laboratory of Neuroscience, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0008.
Mol Pharmacol. 1995 Feb;47(2):363-7.
The ability of volatile (halothane and isoflurane) and nonvolatile (alphaxalone and pentobarbital) general anesthetics to modulate radioligand binding to gamma-aminobutyric acid (GABA)A receptors was examined in an immortalized cell line (WSS-1) expressing rat alpha 1 and gamma 2 subunits. Volatile anesthetics enhance [3H]flunitrazepam binding to WSS-1 cells in a concentration-dependent manner, with potencies and efficacies comparable to those found with native GABAA receptors. Transfection of these cells with cDNAs encoding rat beta 2 or beta 3 subunits had a significant influence on anesthetic efficacy but not potency in this assay. Thus, transfection with the beta 2 subunit reduced the efficacy of both isoflurane and halothane, whereas transfection with the beta 3 subunit increased the efficacy of isoflurane but not halothane, compared with values obtained in WSS-1 cells. In contrast, alpha-xalone (an anesthetic steroid) had no effect, whereas at high concentrations pentobarbital (an anesthetic barbiturate) produced a modest inhibition of [3H]flunitrazepam binding to GABAA receptors in WSS-1 cells. Transfection of WSS-1 cells with cDNAs encoding either beta 2 or beta 3 subunits resulted in a concentration-dependent enhancement of [3H]flunitrazepam binding by these nonvolatile anesthetics. Moreover, pentobarbital was significantly more potent in enhancing [3H]flunitrazepam binding to WSS-1 cells transfected with the beta 2 subunit, compared with the beta 3 subunit. The difference in subunit requirements between volatile and nonvolatile anesthetics for enhancement of [3H]flunitrazepam binding indicates that these classes of agents affect GABAA receptor function at distinct loci. These studies also provide evidence that the beta subunit is required for these nonvolatile anesthetics to positively modulate GABAA receptors.
在表达大鼠α1和γ2亚基的永生化细胞系（WSS - 1）中，研究了挥发性（氟烷和异氟烷）和非挥发性（阿法沙龙和戊巴比妥）全身麻醉药调节放射性配体与γ-氨基丁酸（GABA）A受体结合的能力。挥发性麻醉药以浓度依赖的方式增强[3H]氟硝西泮与WSS - 1细胞的结合，其效力和效能与天然GABAA受体相当。用编码大鼠β2或β3亚基的cDNA转染这些细胞，对该实验中的麻醉效能没有影响，但对麻醉效力有显著影响。因此，与在WSS - 1细胞中获得的值相比，用β2亚基转染降低了异氟烷和氟烷的效能，而用β3亚基转染增加了异氟烷的效能，但未增加氟烷的效能。相比之下，阿法沙龙（一种麻醉类固醇）没有影响，而在高浓度时，戊巴比妥（一种麻醉巴比妥酸盐）对[3H]氟硝西泮与WSS - 1细胞中GABAA受体的结合产生适度抑制。用编码β2或β3亚基的cDNA转染WSS - 1细胞，导致这些非挥发性麻醉药对[3H]氟硝西泮结合的浓度依赖性增强。此外，与β3亚基相比，戊巴比妥在增强[3H]氟硝西泮与用β2亚基转染的WSS - 1细胞结合方面显著更有效。挥发性和非挥发性麻醉药增强[3H]氟硝西泮结合所需亚基的差异表明，这些类别的药物在不同位点影响GABAA受体功能。这些研究还提供了证据，表明β亚基是这些非挥发性麻醉药正向调节GABAA受体所必需的。
