Effects of adenosine and ATP on the membrane potential and synaptic transmission in neurons of the rat locus coeruleus

Effects of adenosine (Ado) and adenosine 5'-triphosphate (ATP) on the membrane potential and synaptic transmission in neurons of the rat locus coeruleus (LC) were examined, in vitro. Ado (30-300 microM) produced a hyperpolarizing response and inhibited spontaneous firing activity in neurons of the rat LC. Ado decreased input resistance of LC neurons. The Ado-induced hyperpolarization reversed polarity near the equilibrium potential of K+ (EK). Ado (100-300 microM) depressed both excitatory postsynaptic potential (EPSP) and inhibitory postsynaptic potential (IPSP). Ado (300 microM) did not alter the hyperpolarization induced by norepinephrine (30 microM). N6-Cyclopentyladenosine (CPA, 100 microM), an A1 receptor agonist, also produced a hyperpolarizing response and depressed both the EPSP and IPSP. Another A1 receptor agonist, adenosine amine congener (ADAC, 30 microM) also produced a hyperpolarizing response and consistently depressed the EPSP and IPSP. Application of ATP (100 microM) to LC neurons caused a depolarizing response associated with an increase in the firing rate of spontaneous action potential in LC neurons. The ATP-induced depolarization was accompanied by an increased input resistance and reversed polarity at--91 mV. ATP (100 microM) consistently depressed the IPSP, while it did not change the amplitude of the EPSP in a majority of neurons. alpha, beta-Methylene ATP (alpha, beta-meATP, 30 micro/M), a P2 receptor agonist, mimicked these effects of ATP. Adenosine 5'-(beta, gamma-imido) triphosphate (AMP-PNP, 100 microM), a non-metabolizable analogue of ATP, produced a depolarizing response in LC neurons, but it produced no obvious depression of the EPSP and IPSP. These results suggest that Ado and ATP cause inhibitory and excitatory modulation, respectively, of neuronal activity and synaptic transmission in the rat LC.     

Effects of methylphenidate on the inhibitory postsynaptic potential in rat locus coeruleus neurons

Effects of methylphenidate (MPH), an agent used clinically for the treatment of children presenting the attention-deficit/hyperactivity disorder (AD/HD), on synaptic transmission in the rat locus coeruleus (LC) were examined by intracellular recording methods. Bath-application of MPH (30 nM-3 microM) increased the amplitude of the inhibitory postsynaptic potential (IPSP), while it did not change the amplitude of the excitatory postsynaptic potential (EPSP). MPH increased the time-to-peak and the half-decay time of the IPSP in LC neurons. MPH increased the amplitude of spontaneous IPSP: individual spontaneous IPSPs merged one into the other so as to produce regular, long-lasting waves of hyperpolarization. Clonidine (10 nM), a selective agonist for alpha 2-adrenoceptors, depressed the IPSP without affecting the EPSP in LC neurons. The results suggest that MPH enhances inhibitory synaptic transmission in the rat LC by depressing the norepinephrine (NE) re-uptake system.     

Methylphenidate enhances inhibitory synaptic transmission by increasing the content of norepinephrine in the locus coeruleus of juvenile rats

The present study examined the effect of methylphenidate (MPH), a psychostimulant, on nor-adrenergic transmission in the locus coeruleus (LC) of juvenile rats. Intracellular recordings showed that MPH (>3 μM) produced a hyperpolarizing response associated with a decrease in the rate of spontaneously firing action potentials. MPH (1 μM) enhanced the amplitude of the inhibitory postsynaptic potential (IPSP) mediated by norepinephrine (NE), but did not change the excitatory postsynaptic potential (EPSP) mediated by excitatory amino acids. Whole-cell patch-clamp recordings showed that MPH (0.3-30 μM) produced an outward current (I(MPH)) and enhanced the inhibitory postsynaptic current (IPSC) in neurons of the juvenile rat LC. MPH (30 μM) enhanced the NE-induced outward current (I(NE)). Bath-application of yohimbine (1 μM) produced an inward current and blocked the MPH-induced enhancement of the IPSC. Yohimbine (1 μM) depressed not only the I(NE) but also the I(MPH) in juvenile rat LC neurons. The current-voltage relationship of the I(MPH) showed inward rectification and reversed polarity at -91.1±4.3 mV (n=5). Ba(2+) (100 μM) blocked the I(MPH), indicating that the I(MPH) is mediated by Ba(2+)-sensitive inward rectifier K(+) current. These results suggest that MPH enhances inhibitory synaptic transmission by increasing the concentration of NE at noradrenergic synapses in juvenile rat LC neurons.     

Effects of interleukin-1 beta on neurons in mammalian pelvic ganglia

The effects of interleukin-1 beta (IL-1 beta) on the membrane potential and synaptic transmission were examined in neurons of mammalian pelvic ganglia. Bath-application of recombinant human IL-1 beta (6-300 pM) for 10 s-5 min produced a long-lasting hyperpolarization associated with increased input resistance in 11 neurons of rat major pelvic ganglia (MPG). In other 8 neurons, IL-1 beta (300 pM) produced a biphasic response that consists of an initial depolarization followed by a long-lasting hyperpolarization. IL-1 beta 163-171 (10-100 pM), a synthetic nonapeptide analog that contains the active domain of human IL-1 beta, mimicked the effect of IL-1 beta in MPG neurons. gamma-Aminobutyric acid (GABA, 300 microM) produced a depolarization followed by a hyperpolarization that was blocked by picrotoxin (100 microM). Db-cyclic guanosine monophosphate (db-cyclic GMP, 100 microM) also produced an initial depolarization followed by a long-lasting hyperpolarization. These results suggest that the IL-1 beta-induced biphasic response is mediated by a GABA receptor-cyclic GMP pathway. IL-1 beta and IL-1 beta 163-171 caused an initial facilitation followed by a long-lasting depression of the excitatory postsynaptic potential (EPSP) in rabbit VPG. The data suggest that IL-1 beta presynaptically depressed the EPSP by reducing the release of acetylcholine (ACh) from the pelvic nerve terminals.     

Effect of acetylcholine on membrane potential in toad dorsal root ganglion neurons and its underlying ionic basis

Intracellular recordings were made to investigate the responses of membrane potential to acetylcholine (ACh) on neurons in isolated toad dorsal root ganglion (DRG). In the 73 neurons examined, 67 were of type A, and the remaining 6 of type C cell. The resting membrane potential of these two types of cells was −67.5±1.3 mV (× ±SE). During the application of ACh (4 × 10^-4–6 × 10^-4 mol/L), the changes in membrane potential were as follows: 1) hyperpolarization, with amplitude of 9.1±3.0 mV (X ± SE; n = 23); 2) depolarization, with amplitude of 12.9 ±2.2 mV (X ±SE; n = 20); 3) biphasic response, i.e., hyperpolarization with amplitude of 8.0±2.4 mV (X±SE) followed by depolarization with amplitude of 10.9±2.1 mV (X±SE) (n=24); no effect (n=6). The hyperpolarization induced by ACh was blocked by superfusion with atropine (1.3 × 10^-5 mol/L; n = 23), while ACh depolarization was blocked by the mixture of d-tubocurarine (1.4 × 10^-5 mol/L) and hexamethonium (1.4 ×10^-5 mol/L) (n = 18). When ACh caused hyperpolarization, the membrane conductance wascin reased by 13.8% and the reversal potential was about -96 mV (n=3). TEA (20 mmol/L) superfusion enhanced ACh depolarization amplitude by 48.2 ±3.2 % (× ± SE;n = 6), and depressed ACh hyperpolarization amplitude by 79.4 ±4.3 % (× ± SE; n= 8).MnCl₂ (4 mmol/l) superfusion decreased the amplitudes of ACh depolarization and hyperpolarization by 54.2 ±7.2 % (X ±SE; n= 5) and by 69.2±6.4 % (X±SE; n = 14) respectively. These results suggest that the depolarization and hyperpolarization induced by ACh are mediated by nicotinic and muscarinic receptors on the soma of toad DRG neurons separately, and it seems that ACh hyperpolarization involves activation of calcium-activated potassium conductance.     

Effects and wavelet spectral entropy analysis of rhubarb extracts rhein on synaptic transmission in rat hippocampal ca1 area in vitro

Background 5-dihydroxyanthraquinone-2-carboxylic acid (rhein) inhibits oxidoreduction induced by reducing nicotingamide adenine dinucleotide in the mitochondria and reducing reactive oxygen species, it also suppresses lipid peroxidation in rat brain homogenates. This study was to assess the effects of anthraquinone derivatives, rhein on synaptic transmission in the rat hippocampal CA1 pyramidal cell layer by intracellular recording.Methods The excitatory postsynaptic potential (EPSP) evoked by stimulation of the Schaffer collaterals in the presence of bicuculline (15 μmol/L) was depressed by application of rhein (0.3－30 μmol/L). The amplitude of the EPSP was restored within 20 minutes after removal of rhein from the supernatant. At a concentration of 30 μmol/L, rhein reduced the amplitude of the EPSP to 42%±3.7% (n=24) of the control. Subsequently, wavelet spectral entropy was used to analyze the EPSP. Results A strong positive correlation was observed between the wavelet spectral entropy and other parameters such as amplitude, slope of rising phase and slope of descending phase of the EPSP. The paired-pulse facilitation (PPF) of the EPSP was significantly increased by rhein (30 μmol/L). The inhibitory postsynaptic potential (IPSP) recorded in the presence of CNQX (20 μmol/L) and APV (40 μmol/L) is not altered by rhein (30 μmol/L). Conclusions Rhein (30 μmol/L) can decrease the frequency but not the amplitude of the miniature EPSP (mEPSP). It is suggested that rhein inhibits excitatory synaptic transmission by decreasing the release of glutamate in rat hippocampal CA1 pyramidal neurons.     

阿扑吗啡对离体蟾蜍交感神经节细胞的作用

应用离体蟾蜍椎旁神经节（ＰＶＧ）细胞内记录技术，初步观察了阿扑吗啡（ＡＰＯ）对交感神经节细胞的作用。ＡＰＯ１，３和１０ｍｍｏｌ／Ｌ灌流３０ｓ分别使６４％（ｎ＝２５），８３％（ｎ＝２４）和１００％（ｎ＝１１）的ＰＶＧ细胞产生浓度依赖性的缓慢去极化反应，在部分细胞可伴有输入膜电阻减少和去极化幅度随膜超极化而增大，但在全部受试细胞均未记录到确切的超极化反应。ＡＰＯ０．１～３ｍｍｏｌ／Ｌ灌流１５ｍｉｎ不仅使全部受试细胞产生去极化反应（ｎ＝２０），还使电刺激交感节前纤维诱发的顺行动作电位起始段上升速率减慢，超极化后电位增大、去极化后电位减小，并在０．３ｍｍｏｌ／Ｌ以上的浓度使顺行动作电位转为兴奋性突触后电位或完全取消突触反应，但对直接动作电位无明显影响。另外，ＡＰＯ还可逆地降低外源性Ａｃｈ电位的幅度（ｎ＝１０）。结果表明ＡＰＯ对离体蟾蜍交感神经节细胞有去极化作用并抑制其胆碱能突触传递。     

Ionic basis of noradrenaline depolarization and hyperpolarization in toad dorsal root ganglia neurones

Summary The membrane conductance and reversal potential were estimated for neurones in toad dorsal root ganglia with intracellular recording technique during depolarization or hyperpolarization induced by noradrenaline (NA). The effects of blocking agents for potassium or calcium ion current on NA-induced membrane potential responses were observed as well. The NA depolarization was accompanied by a 32.6% decrease of membrane conductance. In a few neurones, the membrane conductance showed an initial increase and a following decrease. The NA hyperpolarization was associated with an increase of membrane conductance by 16.2%. The mean reversal potential of NA depolarization was -88.5 ± 0.9mV. The NA hyperpolarization responses were nullified at -89 to -92 mV of membrane potential. TEA superfusion enhanced NA depolarization amplitude by 73.7 ± 11.9% and depressed NA hyperpolarization amplitude by 40.5%. CsCl (intracelluar injection) increased phenylephrine depolarization by 34.5 %. MnCl₂ superfusion decreased the amplitudes of NA depolarization by 50.5 ± 9.9%, and of NA hyperpolarizalion by 89.5±4.9% respectively. The results suggest that depolarization or hyperpolarization induced by NA might be mediated by the alteration of K or Ca channels.     

离体下丘脑视上核神经元的突触反应

目的:了解下丘脑视上核(SON)神经元活动的突触调制机制。方法:应用成年大鼠下丘脑冠状切片SON细胞内记录技术,观察电刺激SON背外侧区域诱发的突触反应。结果:下丘脑视上核神经元兴奋性突触后电位(EPSP)和抑制性突触后电位(IPSP)具有等级性的特点,并呈现明显膜电位依赖关系,即膜超极化时EPSP幅度增大,去极化时减小,而IPSP则相反。细胞旁压力喷射外源性谷氨酸能诱发伴有膜电阻减小的去极化反应。结论:下丘脑冠状脑片中突触联系通路有较好的保存,SON神经内分泌细胞的活动受到兴奋性和抑制性突触传入的调控。     

Delayed rectifier potassium current in dissociated bullfrog primary afferent neurons

Cultured bullfrog dorsal root ganglion cells were voltage-clamped in the whole-cell configuration. The classical delayed rectifier potassium current (IK) was separated from other ionic currents. Tetraethylammonium (1-50 mM) depressed the amplitude of IK in a concentration-dependent manner, a complete block occurring with 30 mM. With the concentration of potassium ions in the superfusate at 20 mM, the reversal potential of IK amounted to about -30mV. IK was activated between -30 and +70 mV. The half activation of IK occurred at +15 mV. The amplitude of IK was increased e-fold with 13.6 mV depolarization. The time constant of IK de-activation was shortened with membrane hyperpolarization (tau congruent to 4 ms at -100 mV). Finally, reciprocal time constant (tau -1) of the de-activating IK was increased e-fold with congruent to 13 mV hyperpolarization. It appears that the properties of IK in amphibian afferent neurons are comparable to those which have been observed with respect to the IK of the squid giant axons (Hodgkin and Huxley, 1952).     

酸中毒对小鼠大脑皮层GABA能神经元电生理特性的影响

目的 探讨胞外酸中毒对小鼠大脑皮层γ-氨基丁酸（GABA）能神经元动作电位发放和突触传递功能的影响。方法 选择出生后27～30 d的小鼠20只,做大脑冠状切片,随后分为正常对照组和细胞外酸中毒组:大脑冠状切片灌流pH值为7.4的人工脑脊液,采用膜片钳全细胞电流钳模式记录动作电位阈电位、绝对不应期和动作电位峰间距,电压钳模式记录自发性兴奋性突触后电流,为正常对照组;随后将灌流人工脑脊液的pH值调为6.5,模拟胞外酸中毒,为细胞外酸中毒组。再次记录神经元动作电位和自发性兴奋性突触后电流,比较两组间以上各项指标的差异。结果 与正常对照组对比,胞外酸中毒使GABA能神经元动作电位峰间距和绝对不应期延长（P<0.01）,阈电位升高（P<0.01）,自发性兴奋性突触后电流幅度和频率增加（P<0.01）。结论 胞外酸中毒损伤大脑皮层GABA能神经元动作电位的发放和突触传递,这可能是酸中毒诱导脑功能损伤的机制之一。     

Adenosine inhibits a GABAB receptor-mediated hyperpolarizing postsynaptic potential in neurons of rat septal nuclei

Intracellular recordings were made from neurons of rat dorsolateral septal nucleus (DLSN), in vitro. Adenosine and 2-chloroadenosine (1-500 microM) hyperpolarized DLSN neurons and blocked the excitatory postsynaptic potential (EPSP) and the late hyperpolarizing potential (LHP) in the presence of bicuculline. Adenosine did not depress the glutamate-induced potential. Bath-application of adenosine depressed the baclofen-induced potential in 60% of the neurons. Adenosine also inhibited the LHP in the remaining 40% of neurons, while it did not depress the baclofen-induced potential in these neurons. These results indicate that adenosine inhibits the EPSP pre-synaptically whereas it inhibits the LHP both pre- and postsynaptically in rat septal nuclei.     

5-HT调制离体脊髓运动神经元活动的作用特征

应用新生大鼠脊髓切片运动神经元(MN)细胞内记录技术,观察5-羟色胺(5-HT)对MN活动的影响(n=50)。发现5-HT在78％MN引起伴有膜电导降低的去极化或内向电流,反应在TTX溶液中持续存在,翻转电位在-90～-105mV,为氟苯氧丙胺增强,但被二甲麦角新碱颉颃。5-HT在8％MN诱发超极化反应,但易于失敏。5-HT在40％MN诱导兴奋和(或)抑制性突触活动,分别对犬尿烯酸和士的宁敏感。结果表明5-HT通过直接或间接方式对MN活动产生兴奋或抑制性调制作用。     

Noradrenaline depolarization and hyperpolarization mediated by alpha-adrenergic receptors in the soma of dorsal root ganglion neurons

Summary Intracellular recordings were made on perfused preparation isolated from toad dorsal root ganglion (DRG). Of the 51 neurones examined, 46 were of type A, and the remaining 5 of type C cell. The resting membrane potential of these two types of cells was ™60.06±1.30 mV ( ±SE). When the preparations were superfused with noradrenaline (NA; 10⁻⁴ ™ 10⁻³M), the changes of Rp were as follows: 1) hyperpolarization, with amplitude of 8.38 ± 1.42mV ( ±SE; 20/48); 2) depolarization, with amplitude of 9.39±1.24mv ( ±SE; 23/48); 3) no effect (5/48). The alteration in membrane potential mentioned above could be neither mimicked by application of isoproterenol, nor blocked by propranolol. Therefore, the possibility of the effect being mediated by β-adrenoceptor could be excluded. Application of phenylephrine and clonidine induced depolarization and hyperpolarization of membrane potential respectively, while application of prazosin eand yohimbine blocked depolarization and hyperpolarization response induced by NA, respectively. From the results mentioned above, it may be concluded that depolarization and hyperpolarization induced by NA are mediated by α₁- and α₂-adrenoceptors on the soma of DRG neurones respectively.     

背索突触后神经元的细胞内电位

麻醉、麻痹猫后,以微电极记录腰骶髓背角背索突触后神经元对电刺激隔离颈髓背索和皮肤感受野的细胞内反应。除记录到逆向电位、顺向电位和自发电位等细胞内电位外,还记录到细胞内突触电位。逆向电位的前电位A-B弯曲不明显。顺向电位、自发电位和突触电位均由前电位、锋电位和后电位组成,锋电位的上升时相上可见A、B成分。突触后电位表现电流效应和频率依赖性,其IPSP具有长时程的抑制作用。结果提示,背索突触后神经元具有相对简化的几何构筑和相当复杂的局部突触回路。     

Electrophysiological properties of neurons of guinea pig celiac ganglia

Summary The present study was carried out to investigate electrophysiological properties of neurons of guinea pig celiac ganglia in vitro. The mean value of resting membrane potential was-59.3 ±5.6 mV (n = 29). The mean values of membrane resistance, time constant and membrane capacity were 53.7±19.8mΩ, 18.4±8.5 ms, and 375.9±175.0 pF (n = 24) respectively. When depolarizing electrotonic potentials induced by application of depolarizing current pulses reached the threshold level, all of the neurons could be made to discharge action potentials. The mean values of amplitude, overshoot, duration of the spikes were 68.0±15.3 mV, 11.7 ±4.6mV, and 2.7±0.6ms (n = 29) respectively. 75% of the neurons tested (n = 29) produced tonic (slow adapting) firing in response to depolarizing current lasting 5 s. The remaining neurons (25%) produced phasic (fast adapting) firing. In addition, fast excitatory postsynaptic potentials or orihodromic action potentials were recorded from 80% of the neurons, antidromic action potentials were recorded from ihe remaining neurons during stimulation of the splanchnic nerves.     

对侧腹外侧索电刺激在新生大鼠脊髓切片运动神经元诱发的突触反应

目的:探讨对侧腹外侧索(cVLF)下行激活对离体脊髓运动神经元(MN)活动的突触调制作用。方法:应用新生大鼠(8~14 d)脊髓切片MN细胞内记录技术,观察cVLF或同侧VLF(iVLF)电刺激在MN所诱发的突触反应。结果:在32个测试的MNs,观察到cVLF电刺激可在21个MNs上诱发去极化反应(即cVLF性兴奋性突触后电位,cVLF-EPSP),在1个MN上诱发超极化反应(即cVLF性抑制性突触后电位,cVLF-IPSP),在4个MNs上诱发cVLF-EPSP后复合有cVLF-IPSP的反应。cVLF-EPSP具有刺激强度依赖性、被低钙高镁溶液取消的特性,与i VLF性EPSP相比,有潜伏期较长的特点(P<0.001)。cVLF-IPSP呈膜电位依赖性,并被印防己毒素(30μmol/L)及士的宁(1.0μmol/L)取消。结论:cVLF的下行激活可通过兴奋性和抑制性突触传递调制MN的活动,其cVLF-IPSP可能由γ-氨基丁酸A受体和(或)甘氨酸受体介导。     

Intrinsic factors involved in the depression of neuronal activity induced by temperature increase in rat hippocampal neurons

The intrinsic factors involved in the temperature-dependent impairment of neuronal activity in hippocampal CA2-CA1 regions were investigated using optical recording techniques. At 32 degrees C, stimulation of the Schaffer collaterals in the hippocampal CA2 region evoked depolarizing optical responses that spread toward the CA1 region. The optical response was characterized by fast and slow components that were mainly related to the presynaptic action potentials and excitatory postsynaptic response, respectively. The increase of the temperature to 38 degrees C was associated with a reversible depression of the neuronal activity in the hippocampal brain preparations. The depression of neuronal activity was irreversible when the temperature was increased to 40 degrees C. In the presence of 22 mM glucose, the depression of the neuronal activity at 38 degrees C was significantly attenuated. Pyruvate (22 mM), but not lactate (22 mM), also improved the depression of neuronal activity induced by the temperature increase. Adenosine (200 microM) strongly depressed the excitatory postsynaptic response, but not presynaptic action potentials. 8-Cyclopentyl-1,3-dimethylxanthine (8-CPT) (10 microM), an adenosine A1 receptor blocker, attenuated the adenosine-induced depression of the excitatory postsynaptic response. 8-CPT (10 microM) prevented the impairment of the excitatory postsynaptic response induced by the increase of the temperature to 38 degrees C. In contrast, the depression of presynaptic action potential at 38 degrees C was not prevented by 8-CPT (10 microM). N omega-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor, and methylcobalamin (10 microM), a vitamin B12 analogue, attenuated the inhibition of pre- and postsynaptic activities induced by the increase of the temperature to 38 degrees C. Glibenclamide, a KATP channel blocker, did not protect neuronal activity from the effects of the increase of the temperature. These results suggest that the heat-induced depression of neuronal activity is mediated by multiple factors, such as impairment of energy metabolism and increase in extracellular adenosine and nitric oxide (NO) levels in hippocampal neurons.     

依托咪酯降低新生大鼠离体脊髓腹角神经元的兴奋性及抑制nAChR的功能

目的 研究依托咪酯（ET）对脊髓腹角神经元电生理特性及烟碱型乙酰胆碱受体（nAChR）的影响。方法 选用19只7~12 d新生SD大鼠,麻醉后,将含有腰骶膨大的脊髓分离并切片,用木瓜蛋白酶（0.18 g/30 mL人工脑脊液）消化切片并孵育40 min,显微镜下选取腹角,用抛光的巴斯德吸管进行急性机械分离神经元,对贴壁的健康神经元结合药理学方法进行穿孔膜片钳记录实验。在电流钳模式下,先记录脊髓腹角神经元自发动作电位（AP）,然后结合预处理给药方式,分别记录不同浓度的ET对脊髓腹角神经元自发AP影响。在电压钳模式下,先应用尼古丁在脊髓腹角神经元诱导出内向电流,然后结合预处理给药方式,记录在不同浓度的ET、不同钳制电位以及不同使用时间的情况下,ET对尼古丁在脊髓腹角神经元诱导的内向电流的影响。结果 急性分离的脊髓腹角神经元状态良好,具有形状多样的胞体和完整的突起;共记录到21例脊髓腹角神经元有自发AP,经0.3、3.0、30.0 μmol/L（3.0 μmol/L相当于临床浓度）不同浓度的ET持续灌流2 min后,与给药前比较,结果12例神经元的AP幅度、锋电位幅度及超射分别被浓度依赖性抑制（P<0.01）;自发放电频率降低（P<0.01）。另外9例神经元的AP被3.0或30.0 μmol/L的ET完全取消;在相同钳制电位下（VH=-70 mV）,分别经0.3、3.0和30.0 μmol/L的ET预处理2 min后,对0.4 mmol/L尼古丁诱导的电流幅度显示出浓度依赖性压抑作用（P<0.01, n=7）。将钳制电位分别设定为-30、-50、-70 mV,应用30.0 μmol/L的ET预处理2 min后,对0.4 mmol/L尼古丁诱导的电流幅度呈电压依赖性压抑作用（P<0.01,每个钳制电位下n=6）。在30.0 μmol/L的ET预处理6 min过程中,分别于0、2、4、6 min时先后4次暴露于0.4 mmol/L的尼古丁（每次暴露时间为2 s）,随着暴露次数增多,尼古丁电流幅度逐渐减小;但若在6 min的预处理过程中,仅在开始（0 min）和结束（6 min）时两次暴露于相同浓度尼古丁,则6 min时,电流幅度抑制率较4次暴露尼古丁时的抑制率明显降低（P<0.01, n=6）。结论 ET以浓度依赖的方式降低脊髓腹角神经元的兴奋性,并且以浓度依赖、电压依赖和使用依赖的方式压抑nAChR功能。     

大鼠脊髓背角胶状质神经元的去极化反跳及调控机制

目的 研究大鼠脊髓背角胶状质(SG)神经元的去极化反跳及调控机制,以期对去极化反跳相关疾病的临床治疗提供参考.方法 选取3～5周龄SD大鼠,制作离体脊髓纵切片,应用全细胞膜片钳技术记录SG神经元的电生理学特点及接受超极化刺激后的反应,并观察超极化激活环核苷酸门控阳离子(HCN)通道阻断剂和T型钙(Cav3)通道阻断剂对去极化反跳的作用.结果 共记录了63个SG神经元的电活动,其中23个无去极化反跳,19个为去极化反跳无放电,21个为去极化反跳伴放电.无去极化反跳组SG神经元的动作电位阈值(-28.7±1.6 mY)明显高于去极化反跳伴放电组(-36.0±2.0 mV)(P＜0.05).HCN通道阻断剂氯化铯和ZD7288可显著延长去极化反跳伴放电的潜伏期,分别从45.9±11.6 ms增加到121.6±51.3ms(P＜0.05)和从36.2±10.3 ms增加到73.6±13.6ms(P＜0.05);ZD7288也能显著延长去极化反跳不伴放电的潜伏期,从71.9±35.1 ms增加到267.0±68.8 ms (P＜0.05),而T型钙通道阻断剂氯化镍和米贝地尔可显著降低去极化反跳伴放电的振幅,分别从19.9±46.3 mV降到9.5±4.5 mV(P＜0.05)和从26.1±9.4 mV降到15.5±5.0mV(P＜0.05),米贝地尔同样能显著降低去极化反跳不伴放电的振幅,从14.3±3.0 mV降低至7.9±2.0 mY(P＜0.05).结论 近2/3的SG神经元有去极化反跳,其潜伏期和振幅分别受HCN通道和T型钙通道调控.