SK channels modulate the excitability and firing precision of projection neurons in the robust nucleus of the arcopallium in adult male zebra finches

Objective Motor control is encoded by neuronal activity. Small conductance Ca2＋-activated K＋ channels （SK channels） maintain the regularity and precision of firing by contributing to the afterhyperpolarization （AHP） of the action potential in mammals. However, it is not clear how SK channels regulate the output of the vocal motor system in songbirds. The premotor robust nucleus of the arcopallium （RA） in the zebra finch is responsible for the output of song information. The temporal pattern of spike bursts in RA projection neurons is associated with the timing of the acoustic features of birdsong. Methods The firing properties of RA projection neurons were analyzed using patch clamp whole-cell and cell-attached recording techniques. Results SK channel blockade by apamin decreased the AHP amplitude and increased the evoked firing rate in RA projection neurons. It also caused reductions in the regularity and precision of firing. RA projection neurons displayed regular spontaneous action potentials, while apamin caused irregular spontaneous firing but had no effect on the firing rate. In the absence of synaptic inputs, RA projection neurons still had spontaneous firing, and apamin had an evident effect on the firing rate, but caused no significant change in the firing regularity, compared with apamin application in the presence of synaptic inputs. Conclusion SK channels contribute to the maintenance of firing regularity in RA projection neurons which requires synaptic activity, and consequently ensures the precision of song encoding.

Bifurcation diagram globally underpinning neuronal firing behaviors modified by SK conductance

Neurons in the brain utilize various firing trains to encode the input signals they have received. Firing behavior of one single neuron is thoroughly explained by using a bifurcation diagram from polarized resting to firing, and then to depolarized resting. This explanation provides an important theoretical principle for understanding neuronal biophysical behaviors. This paper reports the novel experimental and modeling results of the modification of such a bifurcation dia- gram by adjusting small conductance potassium （SK） channel. In experiments, changes in excitability and depolarization block in nucleus accumbens shell and medium-spiny projection neurons are explored by increasing the intensity of injected current and blocking the SK channels by apamin. A shift of bifurcation points is observed. Then, a Hodgkin-Huxley type model including the main electrophysiological processes of such neurons is developed to reproduce the experimental results. The reduction of SK channel conductance also shifts the bifurcations, which is in consistence with experiment. A global bifurcation paradigm of this shift is obtained by adjusting two parameters, intensity of injected current and SK channel con- ductance. This work reveals the dynamics underpinning modulation of neuronal firing behaviors by biologically important ionic conductance. The results indicate that small ionic conductance other than that responsible for spike generation can modify bifurcation points and shift the bifurcation diagram and, thus, change neuronal excitability and adaptation.

沉默JP2基因对小鼠心肌细胞SK2通道的影响

目的:探讨心肌细胞JP2与SK2通道的相互作用。方法:构建靶向小鼠JP2基因的siRNA慢病毒载体(LV-JP2-RNAi-1、LV-JP2-RNAi-2),将其转染至小鼠心肌细胞,以转染空载体(LV-NC-EGFP)和未转染细胞(CtrlNC)作对照。采用实时荧光定量PCR和Western blot法分别检测各组心肌细胞JP2 mRNA和SK2蛋白的表达。结果:转染48 h后,各组小鼠心肌细胞JP2 mRNA表达的差异有统计学意义(F=31.775,P<0.001),LV-JP2-RNAi-1、LV-JP2-RNAi-2组较Ctrl-NC及LV-NC-EGFP组细胞降低。小鼠心肌细胞感染LV-JP2-RNAi-2 72 h后,SK2通道蛋白表达被抑制。结论:沉默小鼠心肌细胞JP2基因可抑制SK2通道的功能。

硝苯地平和SK&F96365对环匹阿尼酸引起的平滑肌细胞质游离Ca^(2+)浓度升高作用的影响

目的 探讨介导 Ca2 +池操纵性 Ca2 +内流的 Ca2 +通道特性。 方法 以 Fura-2荧光探针测定细胞质游离 Ca2 +浓度 ( [Ca2 +] i)。 结果 ( 1 ) 1 0μmol/ L环匹阿尼酸 ( CPA)可触发大鼠主动脉平滑肌细胞 [Ca2 +] i的双相升高 (峰值和持续相 )。 ( 2 ) SK& F963 65( 5～ 4 0 μmol/ L)以浓度依赖性抑制 CPA触发的 [Ca2 +] i升高持续相。 ( 3 )1 μmol/ L硝苯地平阻断电压依赖性 Ca2 +通道后 ,2 0 μmol/ L SK& F963 65仍能抑制 CPA触发的 [Ca2 +] i升高持续相 ;而在 2 0μmol/ L SK& F963 65抑制 CPA触发 [Ca2 +] i升高持续相后 ,1μmol/ L硝苯地平不能产生进一步的抑制作用。 结论 电压依赖性 Ca2 +通道和 Ca2 +池操纵性 Ca2 +通道介导了 Ca2 +池操纵性 Ca2

神经元上的小电导钙激活钾通道的研究进展

小电导的钙激活钾通道 (SK)具有K+ 选择性 ,Ca2 + 高敏性和电压不依赖等特性 ,广泛分布在神经元上。参与产生慢后超级化电位 ,通过放电频率适应影响神经元的放电功能。SK通道主要包括SK1,SK2 ,SK3 3种通道 ,通道活性受Ca2 + ,钙调蛋白 (CaM )以及一些神经递质的调节。SK通道的改变可能与学习记忆失调 。

呋塞米对α_1肾上腺素受体亚型引起的Ca^(2+)内流的影响

目的 探讨Cl-通道开放在不同α1肾上腺素受体亚型引起的Ca2 +内流中的作用。方法 采用Fura 2 /AM荧光分光光度法 ,测定胞浆游离Ca2 +浓度 ,观察Cl-通道阻断剂呋塞米 ,钙通道阻断剂SK&F96 36 5和硝苯地平对不同α1肾上腺素受体亚型 (α1A、α1B AR)引起的Ca2 +内流的影响 ,并加以比较。结果 2 5 ,5和 10 μmol·L-1呋塞米呈浓度依赖性地抑制了α1A和α1B AR亚型引起的Ca2 +内流 ;对α1A AR引起的Ca2 +内流的抑制率分别为 8 3 %± 6 1% ,2 3 8%±14 8%和 40 7%± 19 3% ,对α1B AR引起的Ca2 +内流的抑制率分别为 12 0 %± 5 4% ,19 2 %± 4 9%和 31 9%±4 9%。α1A AR引起的Ca2 +内流被最大抑制浓度 ( 2 0 μmol·L-1)的SK&F96 36 5抑制后 ,不能被 10 μmol·L-1呋塞米进一步抑制 ;而α1B AR引起的Ca2 +内流被 2 0 μmol·L-1SK&F96 36 5抑制后 ,仍能被 10 μmol·L-1呋塞米进一步抑制 ,抑制率为 6 6 %± 3 2 %。结论 参与α1A和α1B AR引起的Ca2

激活脊髓小电导钙离子激活钾通道可抑制小鼠吗啡痛觉过敏

目的探究脊髓小电导钙离子激活钾通道(small conductance Ca^(2+)-activated K^+channels,SK通道)激活后对小鼠吗啡所致痛觉过敏的影响。方法选用♂C57BL6/N小鼠,建立吗啡痛觉过敏模型,鞘内注射SK通道激活剂1-EBIO后,测量小鼠热甩尾潜伏期(tail withdrawal latency,TWL),机械缩足阈值(mechanical withdrawal threshold,MWT)和内脏痛阈的变化。结果吗啡痛觉过敏模型小鼠与生理盐水对照组小鼠相比,热甩尾潜伏期、机械缩足阈值和内脏痛阈均降低;而鞘内注射SK通道激活剂1-EBIO后,与给药前相比,小鼠的痛阈热甩尾潜伏期,机械缩足阈值和内脏痛阈均升高;吗啡模型组小鼠的脊髓SK2膜蛋白表达量较对照组明显降低,而给予1-EBIO后,脊髓SK2膜蛋白表达量较模型组明显升高。结论脊髓SK通道参与小鼠吗啡引起的痛觉过敏。

酪氨酸激酶抑制剂对cyclopiazoni cacid引起的大鼠主动脉血管环收缩效应的影响

目的 探讨酪氨酸激酶在Ca2 +池操纵性Ca2 +内流中的作用。方法 记录大鼠胸主动脉环收缩反应。结果 ①不同剂量酪氨酸激酶抑制剂 genistein (1～ 10 0 μmol·L-1)和tyrphostin 2 5 (Tyr 2 5 ,1～ 30 μmol·L-1)均以浓度依赖性抑制cyclopiazonicacid (CPA)引起的平滑肌收缩平台期。Tyr 2 5的最大作用浓度为 10 μmol·L-1,抑制率为 42 %±11%。② 10 μmol·L-1Tyr 2 5和 1μmol·L-1nifedipine(Nif)对CPA引起电压依赖性Ca2 +通道 (VDCC)开放过程的抑制作用存在部分交叉。③ 1μmol·L-1Nif预处理阻断VDCC作用后 ,10 μmol·L-1Tyr 2 5只能部分阻断CPA引起的Ca2 +池操纵性Ca2 +通道 (SOCC)开放过程 ,再加入 6 0 μmol·L-1SK&F96 36 5可完全阻断SOCC的开放过程。结论 CPA引起平滑肌的收缩过程中 。

巯亚硝基卡托普利对环匹阿尼酸引起的平滑肌细胞胞浆游离Ca^(2+)浓度升高作用的影响

目的 探讨巯亚硝基卡托普利 (S nitrosocaptopril,CapNO)对Ca2 + 池操纵性Ca2 + 内流信号转导过程的影响。方法 以Fura 2荧光探针测定胞浆游离Ca2 + 浓度([Ca2 + ]i)。结果 ①CapNO(2 0～ 12 0 μmol·L-1)呈浓度依赖性抑制环匹阿尼酸 (cyclopiazonicacid ,CPA)引起的[Ca2 + ]i 升高 ,80 μmol·L-1CapNO为最大效应浓度。相同浓度的captopril对CPA升高 [Ca2 + ]i 无明显抑制作用。②在 80 μmol·L-1CapNO抑制CPA引起 [Ca2 + ]i 升高作用的基础上 (31%± 11% ) ;随后加入 1μmol·L-1硝苯地平不能降低 [Ca2 + ]i,再加入 2 0 μmol·L-1SK&F96 36 5 (最大效应浓度 )可进一步降低 [Ca2 + ]i(5 4%± 18% ) ,其中SK&F96 36 5净抑制率为 2 4%± 10 % ,与SK&F96 36 5单独作用抑制率(5 4%± 11% )比较差异有显著性。③不同顺序给予最大效应浓度CapNO (80 μmol·L-1)和tyrphostinAG490 (2 μmol·L-1)对CPA引起 [Ca2 + ]i 升高存在交叉抑制作用。结论 CapNO可通过阻断电压依赖性Ca2 + 通道和Ca2 + 池操纵性Ca2 + 通道抑制CPA引起的 [Ca2 + ]i 升高 ,CapNO对CPA引起 [Ca2 + ]i 升高的阻断作用存在酪氨酸激酶 (Janus2亚型 )

Domesticated HERV-W env contributes to the activation of the small conductance Ca^(2+)-activated K^(+)type 2 channels via decreased 5-HT4 receptor in recent-onset schizophrenia

The human endogenous retroviruses type W family envelope(HERV-W env)gene is located on chromosome 7q21-22.Our previous studies show that HERV-W env is elevated in schizophrenia and HERV-W env can increase cal-cium influx.Additionally,the 5-HTergie system and particularly 5-hydroxytryptamine(5-HT)receptors play a prominent role in the pathogenesis and treatment of schizophrenia.5-hydroxytryptamine receptor 4(5-HT4R)agonist can block calcium channels.However,the underlying relationship between HERV-W env and 5-HT4R in the etiology of schizophrenia has not been revealed.Here,we used enzyme-linked immunosorbent assay to detect the concentration of HERV-W env and 5-HT4R in the plasma of patients with schizophrenia and we found that there were decreased levels of 5-HT4R and a negative correlation between 5-HT4R and HERV-W env in schizophrenia.Overexpression of HERV-W env decreased the transcription and protein levels of 5-HT4R but increased small conductance Ca^(2+)-activated K^(+)type 2 channels(SK2)expression levels.Further studies revealed that HERV-w env could interact with 5-HT4R.Additionally,luciferase assay showed that an essential region(-364 to-176 from the transcription start site)in the SK2 promoter was required for HERV-W env-induced SK2 expression.Importantly,5-HT4R participated in the regulation of SK2 expression and promoter activity.Electrophysiological recordings suggested that HERV-Wenv could increase SK2 channel currents and the increase of SK2 currents was inhibited by 5-HT4R.In condusion,HERV-W env could activate SK2 channels via decreased 5-HT4R,which might exhibit a novel mechanism for HERV-Wenv to influence neuronal activity in schizophrenia.

Potassium Channels: A Potential Therapeutic Target for Parkinson's Disease

The pathogenesis of the second major neurodegenerative disorder, Parkinson’s disease(PD), is closely associated with the dysfunction of potassium(K~+ ) channels. Therefore, PD is also considered to be an ion channel disease or neuronal channelopathy. Mounting evidence has shown that K~+ channels play crucial roles in the regulations of neurotransmitter release, neuronal excitability, and cell volume. Inhibition of K~+ channels enhances the spontaneous firing frequency of nigral dopamine(DA)neurons, induces a transition from tonic firing to burst discharge, and promotes the release of DA in the striatum.Recently, three K~+ channels have been identified to protect DA neurons and to improve the motor and non-motor symptoms in PD animal models: small conductance(SK)channels, A-type K~+ channels, and KV7/KCNQ channels.In this review, we summarize the physiological and pharmacological effects of the three K~+ channels. We also describe in detail the laboratory investigations regarding K~+ channels as a potential therapeutic target for PD.

前庭代偿中双侧前庭内侧核对输入刺激响应的敏感性变化及其离子机制

前庭代偿是研究前庭疾病防治策略和成年后由外周损伤导致的中枢神经系统可塑性的重要模型。脑干中的前庭内侧核(medial vestibular nucleus, MVN)是实现前庭代偿的重要中枢。MVN神经元的兴奋性和敏感性对前庭功能的正常执行十分关键,但先前的研究集中关注于单侧外周迷路切除(unilateral labyrinthectomy, UL)这一前庭代偿模型中患侧MVN中神经元兴奋性活动的变化,对双侧MVN神经元动态响应输入刺激的敏感性变化仍知之甚少。本研究采用实时荧光定量PCR、离体脑片全细胞膜片钳记录和行为学方法,观察到UL后6 h,大鼠表现出显著的自发运动障碍,且其患侧而非健侧MVN中B型神经元的兴奋性活动显著降低。但与之相反,健侧而非患侧MVN中的B型神经元对斜坡和阶跃电流刺激的敏感性则显著升高。UL后1周,大鼠基础运动行为得到代偿,其患侧MVN神经元的兴奋性和健侧MVN神经元的敏感性均恢复至正常水平。此外,参与B型MVN神经元敏感性调控的小电导钙激活钾通道(small conductance Ca^(2+)-activated K^(+)channel, SK) UL后6 h在健侧MVN中选择性表达下调,而1周后恢复至正常水平。药理学选择性阻断健侧MVN中的SK通道以抑制其UL后的功能可塑性变化,可显著延迟前庭运动障碍的代偿。本研究结果提示,患侧MVN神经元兴奋性与健侧MVN神经元敏感性的可塑性变化可能共同参与了前庭症状的产生和前庭代偿,而SK通道可能是介导健侧MVN神经元敏感性随前庭代偿动态变化的重要离子机制。

apamin对日龄雏鸡长时记忆的影响

日龄雏鸡的一次性被动回避学习任务模型被广泛应用于记忆机制研究,具有多方面的优势和便利性.apamin是SK通道(钙离子激活的小电导钾离子通道)的一种选择性阻断剂,以往研究显示其可能增进记忆.但人们对其作用机制的了解不是很充分.使用颅内微量注射方法,在雏鸡中枢记忆相关核团IMM施加apamin,研究其对记忆形成和保持的影响.实验结果显示,雏鸡在弱刺激条件下的被动回避任务中本不能形成稳定的长时记忆,但在训练前短时间内或训练后立即注射适量apamin,可以易化长时记忆的形成.然而,apamin对记忆随时间衰退的过程几乎没有影响,即对记忆保持没有增进作用.此外,在左、右脑IMM单侧注射apamin都可促进记忆形成,但所需剂量高于双侧注射时,且在左侧产生效应的时间早于右侧,这体现了两侧IMM在记忆加工中作用的不对称性.这些结果提示,apamin可能通过阻断中枢记忆相关核团内的SK通道,影响由训练诱发的、与记忆形成有关的某些分子或细胞事件,在一定程度上起到改善记忆的作用.