电鱼小脑浦肯野细胞对急性缺氧的功能反应

目的:通过研究急性缺氧对电鱼(mormyrid electric fish)小脑浦肯野细胞(Purkinje cell,PC)的功能影响,阐明缺氧耐受动物神经元在缺氧条件下的电生理特征。方法:采用全细胞膜片钳记录法,观察急性缺氧对电鱼小脑主神经元PC膜电位、兴奋性和平行纤维(parallel fiber,PF)-PC突触传递的影响。结果:(1)短暂缺氧使电鱼小脑PC膜电位发生迅速而持久的超极化,可持续30 min以上,同时伴随自发放电频率的显著下降。谷氨酸AMPA受体阻断剂CNQX不影响PC缺氧性超极化的产生,但可阻断缺氧性超极化的持续存在;而GABAA受体阻断剂Bicuculline则完全阻断缺氧性超极化的产生,并使膜电位在缺氧开始后发生短暂的去极化。(2)缺氧使PC诱发动作电位的阈值增高,频率减低,幅值减小。(3)急性缺氧使刺激PF诱发的PC兴奋性突触后电流(excitatorypostsynaptic current,EPSC)呈现长时程增强(long term potentiation,LTP),同时使EPSC双脉冲增强现象(pair-pulsefacilitation,PPF)显著衰减。CNQX逆转了PF EPSC的缺氧性LTP,表现为长时程抑制(Long Term Depression,LTD);而Bicuculline则使PF EPSC的缺氧性LTP增强。结论:耐缺氧动物电鱼小脑神经元的缺氧反应特征与哺乳类动物显著不同,AMPA受体和GABAA受体均参与电鱼小脑PC的缺氧性超极化和PF LTP的产生,表明维持GABA能突触和谷氨酸能突触活动的适度平衡,可能是电鱼以及其他耐缺氧动物脑保护机制的关键。     

缺氧对平滑肌膜电位的影响

新鲜分离的猪肺叶内动脉，予以１００％氧气平衡，记录并连续观察其平滑肌膜电位。实验发现，通１００％氮气以降低氧张力时，可引起膜电位快速的超极化反应及其后持续的去极化。去除内皮或细胞外钙离子可致超极化反应完全消失，并使去极化程度降低。提示缺氧引起的超极化反应依赖于内皮和细胞外钙。由此推测缺氧通过外钙内流刺激肺动脉内皮细胞释放内皮源性超极化因子，参与调节急性缺氧性肺血管收缩反应。本实验还记录到平滑肌细胞静息膜电位自发性振荡，缺氧可使其振幅降低，振荡频率稍慢     

大剂量苯巴比妥对惊厥幼鼠浦肯野细胞电生理功能的影响

 目的：研究单次大剂量苯巴比妥对惊厥幼鼠小脑浦肯野细胞(Purkinje cells, PCs)电生理功能的影响。方法：将健康新生7 d (P7) SD幼鼠随机分为正常对照组、惊厥模型组和苯巴比妥组。给予幼鼠腹腔注射戊四氮60 mg/kg制作惊厥模型。苯巴比妥按120 mg/kg一次性腹腔注射。采用全细胞膜片钳记录法在小脑脑片上记录小脑PCs动作电位及PCs兴奋性突触后电流（excitatory postsynaptic current, EPSC）的长时程抑制（long-term depression, LTD）。结果：（1）苯巴比妥组幼鼠小脑PCs诱发动作电位的阈值降低,频率增高。（2）苯巴比妥组幼鼠小脑PCs EPSC幅值在低频刺激后15 min内降低的幅度显著大于其它2组。结论:单次大剂量苯巴比妥增加了惊厥幼鼠小脑PCs的兴奋性,并改变了小脑PCs的突触功能。     

白藜芦醇对人脑皮层锥体神经元Na~+电流缺氧性变化的影响

目的:研究人脑皮层锥体神经元Na~+电流的急性缺氧反应特征以及白藜芦醇(resveratrol,RES)对Na~+电流缺氧反应的影响。方法:采用全细胞膜片钳记录法,在人脑皮层脑片上记录锥体神经元对TTX敏感的电压依赖性Na~+电流,观察急性缺氧和白藜芦醇对Na~+电流幅值和激活性质的影响。结果:(1)急性缺氧使人脑皮层脑片上的锥体神经元Na~+电流呈现短暂的小幅增大后,出现长时程抑制(P0.05),并使Na~+电流的I-V曲线左移(向超极化方向漂移)。(2)AMPA受体阻断剂NBQX阻断了缺氧引起的Na~+电流短暂增大(P0.01),并加剧了Na~+电流的缺氧后抑制(P0.01);GABA_A受体阻断剂Bicuculline对Na~+电流的缺氧性增大和缺氧后抑制无显著性影响(P0.05);二者对缺氧引起的Na~+电流I-V曲线左移均无显著影响。(3)50μmol/L白藜芦醇阻断了Na~+电流的缺氧性增大(P0.01),增强了Na~+电流的缺氧后抑制(P0.05);100μmol/L白藜芦醇显著延迟了Na~+电流的缺氧性反应,使Na~+电流的缺氧性增大现象消失,并使Na~+电流的缺氧后抑制现象衰减(P0.05)。50μmol/L和100μmol/L白藜芦醇均使Na~+电流激活曲线右移,接近正常。结论:人脑皮层锥体神经元Na~+电流对急性缺氧的反应主要表现为长时程抑制;AMPA受体活动可影响Na~+通道对急性缺氧的反应。白藜芦醇对人脑皮层锥体神经元Na~+电流缺氧反应的调节作用与剂量有关,小剂量可模拟NBQX的作用,而大剂量可降低Na~+通道对低氧的敏感性。     

损伤性C类初级感觉神经元膜上唾液酸对其兴奋性的影响

 目的:研究坐骨神经损伤后,大鼠背根神经节(dorsal root ganglion,DRG)C类初级感觉神经元膜表面唾液酸含量变化对其电生理特性的影响。方法:制作大鼠慢性压迫性神经损伤(chronic constriction injury,CCI)痛觉模型,以正常大鼠为对照,采用胞内电生理记录法检测损伤及正常C类神经元的电生理特性,随后用Ca²⁺去中和损伤及正常C类神经元膜表面唾液酸所带负电荷或用唾液酸酶(neuraminidase,NA)分解膜表面唾液酸,观察电生理特性的变化。结果:损伤性C类神经元的静息电位(rest potential,RP)较正常C类神经元移向去极化方向,诱发动作电位(action potential,AP)发生率增加,所需阈强度减小,兴奋性增加;使用Ca²⁺和唾液酸酶使损伤性C类神经元膜电位向超极化方向移动,诱发AP所需阈强度增加,兴奋性降低。而Ca²⁺和唾液酸酶对正常C类神经元的电生理特性及兴奋性无影响。结论:损伤C类神经元膜表面唾液酸含量增加,导致其RP 去极化且兴奋性增加。     

缺氧使非洲电鱼小脑浦肯野细胞之间的GABA能突触传递长时程增强

目的:研究急性缺氧对非洲电鱼小脑浦肯野细胞(Pc)之间γ-氨基丁酸(GABA)能突触传递的影响。方法:采用配对全细胞膜片钳记录法,记录电鱼小脑Pc-Pc之间的抑制性突触后电流(IPSC),观察急性缺氧对Pc-Pc IPSC的影响,以及GABA_A受体拮抗剂和谷氨酸α-氨基-3-羟基-5-甲基-4-异噁唑丙酸(AMPA)受体拮抗剂对Pc-Pc IPSC缺氧反应的调节作用。结果:短暂缺氧使Pc-Pc IPSC的幅值显著增大,表现为长时程增强(LTP);GABA_A受体拮抗剂荷包牡丹碱逆转了Pc-Pc IPSC的LTP,表现为长时程抑制;AMPA受体拮抗剂6-氰基-7-硝基喹喔啉-2,3-二酮(CNQX)阻断了Pc-Pc IPSC的LTP,表现为短时程增强。结论:急性缺氧引起电鱼小脑Pc之间的GABA能突触活动持续增强,GABAA受体和AMPA受体共同介导这种反应,提示GABA能和谷氨酸能突触活动的平衡可能是电鱼以及其他缺氧耐受动物缺氧保护反应的关键机制。     

大鼠脊髓内大麻素CB2受体在芍药苷拮抗吗啡镇痛耐受中的作用

目的:探讨脊髓内大麻素CB2受体在芍药苷拮抗大鼠慢性吗啡镇痛耐受中的作用。方法:成功鞘内置管清洁级Sprague-Dawley(SD)大鼠60只,随机分为4组(n=15):生理盐水组(NS组),吗啡组(MOR组),芍药苷组(PF组)和吗啡+芍药苷组(MOR+PF组)。连续7 d鞘内注射吗啡(15μg)建立慢性吗啡耐受的动物模型。采用50℃热水甩尾潜伏期法(tail flick latency,TFL)和机械反射阈值法(mechanical withdrawal threshold,MWT)观察鞘内注射芍药苷对吗啡镇痛耐受的影响;应用免疫组织荧光染色法检测芍药苷对腰段脊髓小胶质细胞活化的影响;应用免疫印迹法检测芍药苷对腰段脊髓CB2表达的影响。结果:连续7 d鞘内注射吗啡后,与NS组比较,MOR组大鼠腰段脊髓背角小胶质细胞显著增多,腰段脊髓CB2表达显著增加(P0.05);而与MOR组比较,MOR+PF组大鼠腰段脊髓背角小胶质细胞显著减少,腰段脊髓CB2表达显著减少(P0.05)。与MOR组7 d大鼠最大镇痛效应百分率(percent of maximal possible potential effect,MPE)比较,MOR+PF组大鼠MPE显著增加(TFL:19%±4%vs 41%±3%;MWT:18%±6%vs 42%±4%,P0.05)。结论:芍药苷能显著拮抗大鼠慢性吗啡镇痛耐受,其作用机制可能与抑制脊髓内CB2受体表达增加有关。     

HIV-1包膜糖蛋白gp120对大鼠海马脑片电生理特性的影响

目的探讨人类免疫缺陷病毒I型(HIV-1)的包膜糖蛋白gp120对大鼠海马脑片CA1区神经元电生理特性及突触传递的影响。方法用盲法全细胞记录技术,观察gp120对大鼠海马脑片CA1区神经元电生理特性及对高频电刺激Schaffer侧支引起的鼠海马长时程增强效应(LTP)的影响。结果①在电流钳,gp120可使终末去极化电流激发快速动作电位的数目增加;②在电压钳,gp120对大鼠海马CA1区神经元的全细胞电流无明显作用;③将gp120(100 pmol/L)与海马脑片共孵育1h后,在钳制电压为-60 mV时,发现HFS后海马CA1区的兴奋性突触后电流(EPSC)显著减小,LTP的强度减少到(108.5±8.0)%(n=11,P<0.01)。结论gp120可使海马神经元的兴奋性增加,并可能通过抑制海马CA1区的LTP诱发参与艾滋病痴呆(HIV-1 associated dementia,HAD)的病理生理过程。     

催产素减轻新生大鼠海马神经元缺氧缺血性损伤

目的:探讨催产素(oxytocin)对新生大鼠缺氧缺血性损伤后海马CA1区神经元的作用及机制。方法:采用氧糖剥夺(OGD)制备体外缺氧缺血模型,取8只7~10日龄新生大鼠的急性分离脑片(6~8片/只)随机分为4组,即对照组、OGD 20 min组、OGD 40 min组和OGD+oxytocin组,进行TO-PRO-3染色实验观察催产素对神经元的作用。另取20只新生大鼠脑片随机分为4组,分别是OGD组、OGD+oxytocin组、OGD+d VOT(催产素受体阻断剂)+oxytocin组和OGD+bicuculline(GABAA受体阻断剂)+oxytocin组,用全细胞膜片钳记录不同药物作用下海马神经元缺氧去极化的出现时间。结果:TO-PRO-3染色结果显示海马CA1区神经元死亡数量随着氧糖剥夺时间延长而增加,催产素能显著减少OGD所致的死亡神经元数目(P0.05)。全细胞膜片钳记录结果显示,催产素可使缺氧去极化时间显著延长;d VOT及bicuculline可以消除这种效应。结论:催产素能减轻新生大鼠海马CA1区神经元缺氧缺血性损伤,其机制可能是通过结合催产素受体,增强抑制性神经传递,从而产生神经保护作用。     

川芎嗪对牛磺酸引起的交感神经节细胞膜电位变化的影响

实验中将牛磺酸（以任氏液为溶剂配成所需浓度的溶液）按一定时间间隔滴加到含有牛蛙椎旁交感神经节的灌流槽中，以引起交感神经节较为恒定的膜电位反应。采用细胞外微电极技术，记录离体灌流的牛蛙椎旁交感神经节细胞膜电位，观察川芎嗪对牛磺酸介导反应的抑制作用。牛磺酸（10mmol/L)可引起神经节细胞膜超极化（n=38)、去极化（n-14)以及去极化之后伴随超极化过程的双相反应（n=8)、GABAA受体拮抗剂荷包牡丹碱（500μmol/L）可抑制牛磺酸（10mmol/L)的超极化反应（n=6)。无钙溶液灌流对牛磺酸（10mmol/L)介导的反应无影响。川芎嗪 （300μmol/L）可抑制牛磺酸（10mmol/L)的超极化反应（n=13)、去极化反应（n=6)和双相反应（n=4)。结果表明川芎嗪对牛蛙椎旁交感神经节牛磺酸介导的膜电位变化有抑制作用。     

Sevoflurane immediate preconditioning alters hypoxic membrane potential changes in rat hippocampal slices and improves recovery of CA1 pyramidal cells after hypoxia and global cerebral ischemia

Pretreatment with anesthetics before but not during hypoxia or ischemia can improve neuronal recovery after the insult. Sevoflurane, a volatile anesthetic agent, improved neuronal recovery subsequent to 10 min of global cerebral ischemia when it was present for 1 h before the ischemia. The mean number of intact hippocampal cornus ammonis 1 (CA1) pyramidal neurons in rats subjected to cerebral ischemia without any pretreatment was 17+/-5 (neurons/mm+/-S.D.) 6 weeks after the ischemia; na?ve, non-ischemic rats had 177+/-5 neurons/mm. Rats pretreated with either 2% or 4% sevoflurane had 112+/-57 or 150+/-15 CA1 pyramidal neurons/mm respectively (P<0.01) 6 weeks after global cerebral ischemia. In order to examine the mechanisms of protection we used hypoxia to generate energy deprivation. Intracellular recordings were made from CA1 pyramidal neurons in rat hippocampal slices; the recovery of resting and action potentials after hypoxia was used as an indicator of neuronal survival. Pretreatment with 4% sevoflurane for 15 min improved neuronal recovery 1 h after the hypoxia; 90% of the sevoflurane-pretreated neurons recovered while none (0%) of the untreated neurons recovered. Pretreatment with sevoflurane enhanced the hypoxic hyperpolarization(-6.4+/-0.6 vs. -3.3+/-0.3 mV) and reduced the final level of the hypoxic depolarization (-39+/-6 vs. -0.3+/-2 mV) during hypoxia. Chelerythrine (5 muM), a protein kinase C/protein kinase M inhibitor, blocked both the improved recovery (10%) and the electrophysiological changes with 4% sevoflurane preconditioning. Two percent sevoflurane for 15 min before hypoxia did not improve recovery (0% recovery both groups) and did not enhance the hypoxic hyperpolarization or reduce the final depolarization during hypoxia. However if 2% sevoflurane was present for 1 h before the hypoxia then there was significantly improved recovery, enhanced hypoxic hyperpolarization, and reduced final depolarization. Thus we conclude that sevoflurane preconditioning improves recovery in both in vivo and in vitro models of energy deprivation and that preconditioning enhances the hypoxic hyperpolarization and reduces the hypoxic depolarization. Anesthetic preconditioning may protect neurons from ischemia by altering the electrophysiological changes a neuron undergoes during energy deprivation.     

Hypoxia induces an excitotoxic-type of dark cell degeneration in cerebellar Purkinje neurons.

In the rat cerebellar slice preparation, exposure to hypoxia elicited by a 30 min exposure to artificial cerebrospinal fluid continuously gassed with 95% N(2): 5% CO(2) induced a characteristic type of toxicity of Purkinje cells (PCs) resembling excitotoxic-mediated dark cell degeneration (DCD). Morphologically, PCs exhibited marked rounded appearance with cytoplasmic darkening, nuclear condensation and cytoplasmic vacuoles. Using gel electrophoresis, genomic DNA obtained from the cerebellar slice exhibited fragmentation. However, PCs failed to exhibit apoptotic bodies or evidence of phagocytosis, spherical- or crescent-shaped chromatin aggregations or TUNEL-positive staining. Ultrastructural analyses of granule cells revealed the presence of apoptotic bodies and discrete spherical collection of chromatin clumping as well as phagocytosis suggesting that the oligonucleosomal-sized DNA fragments primarily were derived from granule cells. PC-elicited toxicity was attenuated significantly in the presence of the competitive AMPA and NMDA antagonists CNQX and APV, respectively. The present study extends the involvement of excitotoxic processes in mediating hypoxic-induced toxicity of PCs in postnatal rats and suggests, in contrast to DCD elicited by direct application of excitotoxic agents, that DCD associated with acute hypoxic insults in PCs does not resemble classical apoptosis.     

Effect of acute hypoxia on ATP-sensitive potassium currents in substantia gelatinosa neurons of juvenile rats

Although hypoxia is known to affect membrane excitability of various neurons by various mechanisms, the effects of hypoxia on substantia gelatinosa (SG) neurons have not yet been elucidated. In whole-cell or perforated patch-clamp recordings from SG neurons, we showed that acute hypoxia induces a reversible hyperpolarization of –6.1±1.3 mV of the resting membrane potential and an outwards current of 9.48±1.71 pA at a holding potential of –60 mV. The reversal potentials of the hypoxia-induced current depended on [K⁺]_o. The hypoxia-induced hyperpolarization and outwards current were abolished completely by BaCl₂, but not by CsCl. Glibenclamide, a blocker of K_ATP channels, blocked the hypoxia-induced hyperpolarization. Pretreatment with cromakalim, an opener of K_ATP channels, occluded the hypoxia-induced hyperpolarization. Any alteration by hypoxia was not observed in the presence of an internal solution with a high [ATP] (10 mM). The above results suggest that hypoxia-induced hyperpolarization in SG neurons is mediated by activation of K_ATP channels.*Y.K. Park and S.J. Jung contributed equally to this work     

Effects of desflurane and propofol on electrophysiological parameters during and recovery after hypoxia in rat hippocampal slice CA1 pyramidal cells

Cerebral ischemia is a major cause of death and disability and may be a complication of neurosurgery. Certain anesthetics may improve recovery after ischemia and hypoxia by altering electrophysiological changes during the insult. Intracellular recordings were made from CA1 pyramidal cells in hippocampal slices from adult rats. Desflurane or propofol was applied 10 min before and during 10 min of hypoxia (95% nitrogen, 5% carbon dioxide). None of the untreated CA1 pyramidal neurons, 46% of the 6% desflurane- and 38% of the 12% desflurane-treated neurons recovered their resting and action potentials 1 h after hypoxia (P<0.05). Desflurane (6% or 12%) enhanced the hypoxic hyperpolarization (4.9 or 4.7 vs. 2.6 mV), increased the time until the rapid depolarization (441 or 390 vs. 217 s) and reduced the level of depolarization at 10 min of hypoxia (−13.5 or −13.0 vs. −0.6 mV); these changes may be part of the mechanism of its protective effect. Either chelerythrine (5 μM), a protein kinase C inhibitor, or glybenclamide (5 μM), a K_ATP channel blocker, prevented the protective effect and the electrophysiological changes with 6% desflurane. Propofol (33 or 120 μM) did not improve recovery (0 or 0% vs. 0%) 1 h after 10 min of hypoxia; it did not significantly enhance the hypoxic hyperpolarization (3.6 or 3.1 vs. 2.6 mV) or increase the latency of the rapid depolarization (282 or 257 vs. 217 s). The average depolarization at 10 m of hypoxia with 33 μM propofol (−4.1 mV) was slightly but significantly different from that in untreated hypoxic tissue (−0.6 mV). Desflurane but not propofol improved recovery of the resting and action potentials in hippocampal slices after hypoxia, this improvement correlated with enhanced hyperpolarization and attenuated depolarization of the membrane potential during hypoxia. Our results demonstrate differential effects of anesthetics on electrophysiological changes during hypoxia.     

Sulfhydryl oxidation reduces hippocampal susceptibility to hypoxia-induced spreading depression by activating BK channels

The cytosolic redox status modulates ion channels and receptors by oxidizing/reducing their sulfhydryl (SH) groups. We therefore analyzed to what degree SH modulation affects hippocampal susceptibility to hypoxia. In rat hippocampal slices, severe hypoxia caused a massive depolarization of CA1 neurons and a negative shift of the extracellular DC potential, the characteristic sign of hypoxia-induced spreading depression (HSD). Oxidizing SH groups by 5,5'-dithiobis 2-nitrobenzoic acid (DTNB, 2 mM) postponed HSD by 30%, whereas their reduction by 1,4-dithio-dl-threitol (DTT, 2 mM) or alkylation by N-ethylmaleimide (500 microM) hastened HSD onset. The DTNB-induced postponement of HSD was not affected by tolbutamide (200 microM), dl-2-amino-5-phosphonovaleric acid (150 microM), or 6-cyano-7-nitroquinoxaline-2,3-dione (25 microM). It was abolished, however, by Ni2+ (2 mM), withdrawal of extracellular Ca2+, charybdotoxin (25 nM), and iberiotoxin (50 nM). In CA1 neurons DTNB induced a moderate hyperpolarization, blocked spontaneous spike discharges and postponed the massive hypoxic depolarization. DTT induced burst firing, depolarized glial cells, and hastened the onset of the massive hypoxic depolarization. Schaffer-collateral/CA1 synapses were blocked by DTT but not by DTNB; axonal conduction remained intact. Mitochondria did not markedly respond to DTNB or DTT. While the targets of DTT are less clear, the postponement of HSD by DTNB indicates that sulfhydryl oxidation increases the tolerance of hippocampal tissue slices against hypoxia. We identified as the underlying mechanism the activation of BK channels in a Ca(2+)-sensitive manner. Accordingly, ionic disregulation and the loss of membrane potential occur later or might even be prevented during short-term insults. Therefore well-directed oxidation of SH groups could mediate neuroprotection.     

Effect of hypoxia on membrane potential and resting conductance in rat hippocampal neurons.

The present patch-clamp study describes the effect of hypoxia at 30-31 degrees C on membrane potential and resting conductance in pyramidal cells from the hippocampal CA1 region in rat brain slices. The initial effect of hypoxia was a gradual hyperpolarization; the peak change in membrane potential measured over 15 min was -5.3 +/- 0.22 mV (P < 0.0001). After reoxygenation followed a transient hyperpolarization measuring -1.8 +/- 0.24 mV (P < 0.0001) and a subsequent normalization of the membrane potential, which after 5 min did not differ from its level prior to the hypoxic episode. Voltage-clamp analysis showed that the hypoxic hyperpolarization was related to an outward current at the holding potential (-60 mV) and an increase in resting conductance. The effect was not influenced by intracellular Cl- concentration, which indicated that it was not due to an inward flow of Cl- ions. The addition of tolbutamide, glibenclamide and dantrolene sodium did not affect the hypoxic hyperpolarization, neither did the presence of ATP in the pipette solution. The presence/absence of glucose in the perfusion medium did not influence the initial hyperpolarization during hypoxia; however, glucose seemed to prevent the subsequent depolarization under hypoxia. It was concluded that hypoxia caused an initial hyperpolarization of CA1 cells which was related to an increase in the resting conductance. The results did not suggest the involvement of ATP-sensitive K+ channels.     

Role of TRP channels and NCX in mediating hypoxia-induced [Ca(2+)](i) elevation in PC12 cells

Mammalian cells require a constant O2 supply to produce adequate energy, and sustained hypoxia can kill cells. Mammals therefore have evolved sophisticated mechanisms to allow their cells to adapt to hypoxia. In this study, we investigated the role of TRP channels and the Na+-Ca2+ exchanger (NCX) in mediating hypoxia-induced [Ca2+]i elevation in a model of the O2-sensing rat pheochromocytoma (PC12) cell line by using Ca2+ imaging and molecular biological approaches. Non-selective cation channels, such as TRPC1, 3 and 6, were found to be functionally expressed in PC12 cells. They mediated Ca2+ entry when cells were exposed to acute hypoxia (PO2 of 15 mmHg), in addition to Ca2+ entry via VGCCs. Blockage of TRPCs by 2APB and SKF96365 could significantly reduce hypoxia-mediated [Ca2+]i elevation. Suramin and U73122 attenuated the hypoxia-induced [Ca2+]i elevation, implying the involvement of the G-protein and PLC pathways in the hypoxic response. In addition to TRPCs and VGCCs, NCX also contributed to the hypoxia-induced [Ca2+]i elevation, and blockade of NCX by KBR7943 could significantly decrease the hypoxia-induced [Ca2+]i elevation. Our results suggest that the activation of TRP by hypoxia could lead to NCX reversal; furthermore, membrane depolarization and TRPCs may play a primary role in mediating the hypoxic response in PC12 cells.