Ming Zhen, Griffith Benjamin L, Breese George R, Mueller Robert A, Criswell Hugh E
Anesthesiology, Bowles Center for Alcohol Studies, School of Medicine, University of North Carolina at Chapel Hill, 27599, USA.
Anesthesiology. 2002 Oct;97(4):856-67. doi: 10.1097/00000542-200210000-00017.
Developmental changes in NR1 splice variants and NR2 subunits of the N-methyl-D-aspartate (NMDA) receptor have been associated with changes in the sensitivity of NMDA receptors to agonists, antagonists, and pharmacologic modulators. The authors have investigated changes in the effect of isoflurane on NMDA-gated currents from cultured cortical neurons with time in culture and related these changes to the subunit composition of the NMDA receptors.
N-methyl-D-aspartate-gated currents were measured using whole-cell voltage clamp recording in cortical neurons cultured for 1-4 weeks and HEK 293 cells transiently expressing NR1-1a + NR2A or NR1-1a + NR2B subunit-containing receptors. NMDA alone or NMDA with treatment agents (isoflurane or ifenprodil) was applied to cells using a U tube.
The effect of isoflurane and the NR2B selective antagonist ifenprodil on NMDA-gated currents from cortical neurons decreased significantly with time in culture. NMDA-gated currents mediated by NR2A-containing receptors were less sensitive to isoflurane than those mediated by NR2B-containing receptors. Tachyphylaxis to repeated application of isoflurane was found in cortical neurons and HEK 293 cells with recombinant NMDA receptors. Hooked tail currents were induced by isoflurane in cultured cortical neurons and HEK 293 cells with expressed NMDA receptors.
Isoflurane inhibits NMDA-gated currents at concentrations well below 1 minimum alveolar concentration (MAC). This effect of isoflurane was subunit dependent with the NR2B-containing receptors more sensitive to isoflurane than the NR2A-containing receptors. A potent tachyphylaxis occurred after brief exposure to isoflurane.
N-甲基-D-天冬氨酸（NMDA）受体的NR1剪接变体和NR2亚基的发育变化与NMDA受体对激动剂、拮抗剂和药理调节剂的敏感性变化有关。作者研究了异氟烷对培养的皮质神经元中NMDA门控电流的影响随培养时间的变化，并将这些变化与NMDA受体的亚基组成相关联。
使用全细胞膜片钳记录法，在培养1 - 4周的皮质神经元以及瞬时表达含NR1-1a + NR2A或NR1-1a + NR2B亚基受体的HEK 293细胞中测量N-甲基-D-天冬氨酸门控电流。使用U型管将单独的NMDA或与治疗剂（异氟烷或艾芬地尔）一起的NMDA施加到细胞上。
异氟烷和NR2B选择性拮抗剂艾芬地尔对皮质神经元NMDA门控电流的影响随培养时间显著降低。含NR2A受体介导的NMDA门控电流对异氟烷的敏感性低于含NR2B受体介导的电流。在具有重组NMDA受体的皮质神经元和HEK 293细胞中发现了对重复应用异氟烷的快速耐受性。异氟烷在培养的皮质神经元和表达NMDA受体的HEK 293细胞中诱导出钩状尾电流。
异氟烷在远低于1个最低肺泡浓度（MAC）的浓度下抑制NMDA门控电流。异氟烷的这种作用是亚基依赖性的，含NR2B的受体比含NR2A的受体对异氟烷更敏感。短暂暴露于异氟烷后会出现强烈的快速耐受性。
