VARIATION IN I(H), I(IR), AND I(LEAK) BETWEEN ACUTELY ISOLATED ADULT-RAT DORSAL-ROOT GANGLION NEURONS OF DIFFERENT SIZE
VARIATION IN I(H), I(IR), AND I(LEAK) BETWEEN ACUTELY ISOLATED ADULT-RAT DORSAL-ROOT GANGLION NEURONS OF DIFFERENT SIZE
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DOI：
10.1152/jn.1994.71.1.271
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发表时间：
1994-01-01
影响因子：
2.5
通讯作者：
FOX, AP
中科院分区：
文献类型：
--
作者：
SCROGGS, RS;TODOROVIC, SM;FOX, AP
1.本文研究了不同直径的大鼠背根神经节（DRG）神经元胞体（神经元）中I-H、I-IR和I-LEAK的分布。DRG神经元在三个直径范围内进行了研究：小（19-27 μ m），中（33-37 μ m），和大（44-54 μ m）。I-H被定义为从-60 mV的保持电位（HP）开始由超极化电压阶跃诱发的缓慢激活的内向电流，并且被1 mM Cs 2+阻断，但不被1 mM Ba 2+阻断。内向整流电流（I-IR）定义为由HP-60 mV超极化诱发的快速激活电流，该电流在钾的反转电位（E（K））附近向内整流，并被100 μ M Ba ~（2+）完全阻断。I-LEAK定义为HP-60 mV时的外向静息电流，该电流不整流，可被100 μ M Ba ~（2+）阻断，但不被2 mM Cs ~（2+）阻断。2. I-H在23/23个大直径DRG神经元、11/12个中等直径DRG神经元和9/20个小直径DRG神经元中观察到。峰值I-H归一化膜表面积显着大于在中或小直径DRG神经元表达I-H。在电压钳条件下，所有表现出I-H的神经元都具有短持续时间的动作电位，并在电流钳条件下表现出时间依赖性整流，其性质类似于A型DRG神经元。11个不表达I-H的小直径神经元具有长持续时间的动作电位，并且没有表现出时间依赖性整流，类似于C型DRG神经元的特性。3. 22个中等直径神经元中有18个检测到I-IR。当使用玻尔兹曼方程的形式建模时，I = [G（IN）（V-E（IN））] +（G（IR，MAX）（V-E（K））/{1 + exp[（V-V-1/2）/k]}），G（IR，MAX）在这18个神经元中平均为13.3 +/-0.8（SE）nS。V-1/2平均值为-96.4 +/- 2.3（SE）mV，k平均值为17.4 +/- 1.1（SE）mV。大直径神经元（4/30）或小直径神经元（3/20）很少观察到向内整流。4.在28个大直径神经元中的15个中检测到I-LEAK，在用1 mM Ba 2+灌注后，保持电流（HP-60 mV）内移0.7 +/- 0.12（SE）nA。在-110 mV的测试电位下，保持电流的向内偏移与58 +/-4.4%（SE）的弦电导（快电流）阻滞相关。在15个表达I-LEAK的神经元中，有14个细胞的Ba ~（2+）敏感快电流在一系列超极化电压阶跃中呈线性电流-电压（I-V）关系。Ba ~（2+）敏感电流的翻转电位平均为-78 +/-1.4（SE）mV（n = 10）。Ba 2+敏感的I-LEAK在中等直径神经元（2/12）或小直径神经元（2/8）中表达较少。5.结论：I-H、I-IR和I-LEAK在不同直径DRG细胞中的表达差异显著。感官形态可能会有所不同的三个直径组研究。因此，单个离子电流的调制可以导致不同类型的感觉信息的选择性过滤。在急性分离的DRG神经元中观察到的离子电流表达的变化可以解释在A型和C型DRG神经元之间观察到的输入电阻和时间依赖性整流的差异，从细胞内记录在完整的神经节。
1. The distribution of I-H,I-IR, and I-LEAK was studied in different diameter rat dorsal root ganglion( DRG) neuron cell bodies(neurons). DRG neurons were studied in three diameter ranges: small (19-27 mu m), medium(33-37 mu m), and large(44-54 mu m). I-H was defined as a slowly activating inward current evoked by hyperpolarizing voltage steps from a holding potential (HP) of -60 mV, and blocked by 1 mM Cs2+ but not 1 mM Ba2+. Inward rectifier current (I-IR) was defined as a rapidly activating current evoked by hyperpolarizations from HP -60 mV, which rectified inwardly around the reversal potential for potassium (E(K)), and was completely blocked by 100 mu M Ba2+. I-LEAK was defined as an outward resting current at HP -60 mV, which did not rectify and was blocked by 100 mu M Ba2+ but not by 2 mM Cs+. 2. I-H was observed in 23 of 23 large, 11 of 12 medium, and in 9 of 20 small diameter DRG neurons tested. Peak I-H normalized to membrane surface area was significantly greater in large than in medium or small diameter DRG neurons expressing I-H. All neurons exhibiting I-H under voltage clamp conditions had short duration action potentials and exhibited time-dependent rectification under current clamp conditions, properties similar to A-type DRG neurons. The 11 small diameter neurons not expressing I-H had long duration action potentials and did not exhibit time-dependent rectification, properties similar to C-type DRG neurons. 3. I-IR was detected in 18 of 22 medium diameter neurons tested. When modeled using a form of the Boltzmann equation, I = [G(IN)(V-E(IN))] + (G(IR,MAX)(V-E(K))/{1 + exp[(V-V-1/2)/k]}), G(IR,MAX) averaged 13.3 +/- 0.8 (SE) nS in these 18 neurons. V-1/2 averaged -96.4 +/- 2.3 (SE) mV and k averaged 17.4 +/- 1.1 (SE) mV. Inward rectification was infrequently observed in large diameter neurons (4 out of 30) or small diameter neurons ( 3 out of 20). 4. I-LEAK was detected in 15 of 28 large diameter neurons by a 0.7 +/- 0.12 (SE) nA inward shift in holding current(HP -60 mV), after superfusion with 1 mM Ba2+. The inward shift in holding current was associated with a 58 +/- 4.4% (SE) block of chord conductance (fast current) at a test potential of -110 mV. The Ba2+ sensitive fast current in 14 of 15 neurons expressing I-LEAK had a linear current-voltage (I-V) relationship throughout a series of hyperpolarizing voltage steps. The reversal potential of the Ba2+ sensitive current in these neurons averaged -78 +/- 1.4 (SE) mV (n = 10). Ba2+-sensitive I-LEAK was less frequently expressed in medium diameter neurons (2 of 12) or small diameter neurons (2 of 8). 5. In conclusion, the expression of I-H, I-IR, and I-LEAK in different diameter DRG cells varied significantly. Sensory modality is likely to vary among the three diameter groups studied. Thus the modulation of individual ion currents could result in selective filtering of different types of sensory information. The variations in ion current expression observed in acutely isolated DRG neurons can explain the differences in input resistance and time-dependent rectification observed between A- and C-type DRG neurons recorded from intracellularily in intact ganglia.