Ionic mechanisms of intrinsic oscillations in neurons of the basolateral amygdaloid complex
Ionic mechanisms of intrinsic oscillations in neurons of the basolateral amygdaloid complex
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DOI：
10.1152/jn.1998.79.1.217
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发表时间：
1998-01-01
影响因子：
2.5
通讯作者：
Driesang, RB
中科院分区：
文献类型：
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作者：
Pape, HC;Driesang, RB
在体外制备的豚鼠杏仁核切片中，研究了杏仁核基底外侧复合体内一类棘神经元发生低阈值(LTO)和高阈值(HTO)振荡的离子机制。局部应用河豚毒素(TTX，10-20muM)或将胞外钠离子浓度([Na+](O))从153 mM降至26 mM可消除LTO，而在这些条件下更容易诱发HTO。TTX和低[Na+]的作用伴随膜电位超极化位移3+/-1 mV和表观输入电阻降低14+/-11M欧米加。用含有微管的QX314(50µM)或Cs-乙酸酯(2M)进行细胞内记录时，未观察到LTO。在与LTO产生相关的膜电位下，正弦电流输入的电压响应在0~10 HZ之间变化，在2.4+/-1 HZ的响应(共振)中有一个峰值，与LTO的频率范围基本一致。共振行为在阻抗幅度图(ZA图)中出现峰值，在快速傅立叶变换(FFT)中出现极大值。TTX和Ba2+(Ba2+；2-10 mM)同时降低共振和LTO，并在胞外Cs(Cs+；10-30 mM)或四乙基氯化铵(TEA；20-50 mM)作用下被保存，尽管TEA的频域峰值倾向于向较低的值移动。卡巴胆碱(50-200 mU M)可显著减少或阻断LTO，而4-氨基吡啶(4-AP；10 mM)、IBTX(10 MU M)和阿帕明(20 MM)则不起作用。慢去极化/复极化电流斜波(12.5-125pA/S)在电流斜波的任一相引起膜电位的节律性偏转。用镁替代细胞外钙(Ca~(2+))和添加氯化钴(2-4 mM)可阻断HTO，但对细胞产生LTO的倾向无明显影响。用含有200 mm的双-(2-氨基苯氧基)-N，N，N‘，N’-四乙酸(BAPTA；200 mm)微管刺入细胞后，HTO在类似的10分钟内被清除。细胞内Cs+、细胞外Ba2+(2-10 mM)或细胞外TEA(20-50 mM)引起节律性放电幅度增加，复极时程逐渐减慢，直至在-20~-10 mV达到稳定的去极化。应用IBTX(10mU M)可逆性地抑制电流坡道复极阶段的节律活动，而应用河豚毒素(2-10mU M)和阿帕明(20mM)则不起作用。用含KNO3(3 M)的微管记录细胞内氯(Cl-)平衡电位约+30 mV，或将[Cl-](O)从128 mm降低到4 mm，或通过尼氟米酸(100 MM)阻断氯电导，对LTO或HTO没有显著影响。细胞外钙离子的去除和与HTO相关的HTO的阻断显著影响了膜去极化重复尖峰模式的产生，取消了最初的高频放电，延迟了对慢节奏放电的频率适应，在强去极化刺激下以更不规则的模式发生放电。结论是TTX敏感的Na+电导和M电流有助于LTO的产生，但它们在心律失常发生中的确切作用仍有待确定。HTO似乎在很大程度上依赖于高电压激活的钙电导、推测通过BKCa通道的钙激活的K+电流和额外的电压依赖的K+电导之间的功能耦合。在功能方面，HTO在确定维持去极化影响期间对慢节奏放电模式的尖峰频率适应性方面是重要的。
Ionic mechanisms underlying low-threshold (LTO) and high-threshold (HTO) oscillations occurring in a class of spiny neurons within the basolateral amygdaloid complex (see companion paper) were investigated in slice preparations of the guinea pig amygdala in vitro. LTOs were abolished through local application of tetrodotoxin (TTX, 10-20 mu M) or a decrease in the extracellular sodium concentration ([Na+](o)) from 153 to 26 mM, whereas HTOs were more readily elicited under these conditions. The effects of TTX and low [Na+], were accompanied by a hyperpolarizing shift of the membrane potential by 3 +/- 1 mV and a decrease in apparent input resistance by 14 +/- 11 M Omega. LTOs were not observed during intracellular recording with QX 314 (50 mu M) or Cs-acetate (2 M) containing micropipettes. At membrane potentials associated with LTO generation, voltage responses to sinusoidal current input with changing frequency between 0 and 10 Hz were characterized by a peak, in the response (resonance) at 2.4 +/- 1 Hz, largely corresponding to the frequency range of the LTOs. Resonance behavior was evident as a peak in the impedance amplitude plot (ZA-plot) and a maximum in the fast Fourier transformation (FFT). Resonance and LTOs were concomitantly reduced by TTX and barium (Ba2+; 2-10 mM) and were preserved during action of extracellular cesium (Cs+; 10-30 mM) or tetraethylammonium chloride (TEA; 20-50 mM), although the peak in the frequency domain tended to shift to lower values in TEA. Application of carbachol (50-200 mu M) significantly reduced or blocked LTOs, whereas 4-aminopyridine (4-AP; 10 mM), iberiotoxin (Ibtx, 10 mu M), and apamin (20 mu M) had no effect. Slow depolarizing/repolarizing current ramps (12.5-125 pA/s) evoked HTOs as rhythmic deflections in membrane potential at either phase of the current ramp. Substitution of extracellular calcium (Ca2+) by magnesium and addition of cobalt chloride (2-4 mM) blocked HTOs but had no measurable effect on the propensity of the cells to produce LTOs. HTOs were abolished within similar to 10 min after impalement of the cells with a bis-(2-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA; 200 mM)-containing micropipette. Intracellular Cs+, extracellular Ba2+ (2-10 mM), or extracellular TEA (20-50 mM) induced an increase in amplitude of the rhythmic discharges and an increasingly slowed time course of repolarization at successive oscillatory events, until a steady depolarization was reached at -20 to -10 mV. Application of Ibtx (10 mu M) reversibly abolished rhythmic activity during the repolarizing phase of the current ramp, whereas charybdotoxin (2-10 mu M) and apamin (20 mu M) had no effect. Changes in the chloride (Cl-) equilibrium potential by approximately +30 mV through intracellular recording with a KNO3 (3 M)-containing micropipette or lowering [Cl-](o) from 128 to 4 mM, or blockade of Cl- conductances through niflumic acid (100 mu M), did not significantly effect LTOs or HTOs.The generation of repetitive spike patterns on membrane depolarization was substantially influenced through removal of extracellular Ca2+ and associated blockade of HTOs, in that the initial high frequent discharge was abolished, frequency adaptation toward slow-rhythmic firing was delayed, and firing occurred at a more irregular pattern during strong depolarizing stimuli. It is concluded that a TTX-sensitive Na+ conductance and the M current contribute to generation of the LTOs, although their exact role in rhythmogenesis remains to be determined. HTOs seem to largely depend on a functional coupling between high-voltage-activated Ca2+ conductances, a Ca2+-activated K+ current presumably carried through BKCa channels, and additional voltage-dependent K+ conductances. In functional terms, the HTOs are important in determining spike frequency adaptation toward a slow-rhythmic firing pattern during maintained depolarizing influence.