Postnatal rat nigrostriatal dopaminergic neurons exhibit five types of potassium conductances.
Postnatal rat nigrostriatal dopaminergic neurons exhibit five types of potassium conductances.
复制标题
出生后大鼠黑质纹状体多巴胺能神经元表现出五种类型的钾电导。
作者：
N. Silva;C. Pechura;J. Barker
1.用全细胞膜片钳记录技术研究了新生大鼠黑质致密带(SNZC)急性分离神经元的电特性。用罗丹明标记的荧光乳胶微球鉴定逆行标记的黑质纹状体神经元。SNZC内90%以上的罗丹明标记神经元显示甲醛/戊二醛诱发的儿茶酚胺荧光，表明它们是多巴胺能神经元。2.DA神经元有15-20微米的卵圆形或梭形胞体，近端有2-3个粗大突起。标记神经元产生规则和不规则模式的自发动作电位活动。这些细胞的输入电阻为300-600兆欧加，动作电位幅度为60-80 mV。局部应用多巴胺通过使细胞超极化来抑制这些神经元的自发活动。3.用含河豚毒素(TTX)的介质作电压钳记录，检测外向电流。在所有DA细胞中，去极化电压指令激活外向电流的几个分量，取决于细胞的保持电位。当细胞被保持在-40 mV(或更正)时，电压阶跃激活了持续的外向电流。如果膜电位保持在-50 mV以上，也可以检测到外向电流反应的快速激活和失活成分。4.从超极化保持电位(-90 mV)开始，用去极化指令激活的瞬时外向电流达到-55 mV，在5ms内达到峰值。失活电流的单指数时间常数为53+/-4(SE)ms。在较正的保持电位(-40 mV)下，施加条件性超极化预脉冲可以消除电流的稳态失活。在固定的去极化电压阶跃下，半最大失活发生在-65 mV左右。瞬时电流被4-氨基吡啶(4-AP)阻断。5.将细胞保持在-40 mV，分离出持续的外向电流。持续外向电流的两种成分对钙通道阻滞剂Co2+(5 MM)和/或CD2+(200微米)的敏感性不同。在有Co2+/Cd2+存在的情况下，剩余电流由正值大于-40 mV的去极化电压指令激活。
1. We have investigated the electrical properties of neurons acutely dissociated from the substantia nigra zona compacta (SNZC) of the postnatal rat with whole cell patch-clamp recordings. Retrogradely labeled nigrostriatal neurons were identified with the use of rhodamine-labeled fluorescent latex microspheres. Over 90% of the rhodamine-labeled neurons in the SNZC demonstrated formaldehyde/glutaraldehyde-induced catecholamine fluorescence, indicating that they were dopaminergic (DA) neurons. 2. DA neurons had 15-20 microns ovoid or fusiform-shaped cell bodies with 2-3 thick proximal processes. Labeled neurons generated spontaneous action-potential activity in both regular and irregular patterns. These cells exhibited input resistances of 300-600 M omega and action-potential amplitudes of 60-80 mV. Locally applied dopamine inhibited the spontaneous activity of these neurons by hyperpolarizing the cells. 3. Outward currents were examined with voltage-clamp recordings using a tetrodotoxin (TTX)-containing medium. In all DA cells, depolarizing voltage commands activated several components of outward current depending on the holding potential of the cell. When cells were held at -40 mV (or more positive), voltage steps activated a sustained outward current. If the membrane potential was held more negative than -50 mV, a rapidly activating and inactivating component of outward current response could also be detected. 4. From a hyperpolarized holding potential (-90 mV) the transient outward current activated with depolarizing commands to -55 mV, peaking within 5 ms. The current inactivated with a monoexponential time constant of 53 +/- 4 (SE) ms. At more positive holding potentials (-40 mV) the steady-state inactivation of the current could be removed by applying a conditioning hyperpolarizing prepulse. In response to a fixed depolarizing voltage step, half-maximal inactivation occurred at about -65 mV. The transient current was blocked by 4-aminopyridine (4-AP). 5. The sustained outward currents were isolated by holding the cells at -40 mV. Two components of sustained outward current were distinguished by their sensitivity to the calcium channel blockers Co2+ (5 mM) and/or Cd2+ (200 microM). The current remaining in the presence of Co2+/Cd2+ was activated by depolarizing voltage commands more positive than -40 mV.(ABSTRACT TRUNCATED AT 400 WORDS)