Lang E J, Paré D
Department of Physiology and Neuroscience, New York University Medical Center, NY 10016, USA.
Neuroscience. 1998 Apr;83(3):877-89. doi: 10.1016/s0306-4522(97)00420-x.
Previous work in our laboratory has revealed that the excitability of lateral amygdaloid projection neurons is tightly regulated by GABA-mediated inhibitory postsynaptic potentials and intrinsic conductances that can be activated by synaptic inputs. Here, we studied the synaptic responsiveness of lateral amygdaloid interneurons recorded intracellularly in vivo, in the cat, to investigate their role in regulating the activity of projection cells. Interneurons were identified morphologically by their aspiny dendritic trees and physiologically by their ability to generate high frequency, non-adapting spike trains in response to depolarizing current pulses. Cortical shocks of increasing intensity generated opposite response profiles in interneurons and projection cells, with interneurons becoming progressively more excited and projection cells more inhibited. These cortically-evoked response profiles paralleled the activity of interneurons and projection cells in relation to spontaneous electroencephalographic events of differing amplitudes. Only at the lowest intensities were predominantly excitatory responses elicited in both cell types. As a result, only a narrow range of low stimulus intensities could trigger spikes in projection cells. In both cell types, the initial cortically-evoked excitatory postsynaptic potential was followed by a hyperpolarization, which was of markedly lower amplitude and duration in interneurons. In interneurons, the hyperpolarization reversed at approximately -72 mV with potassium acetate pipettes and approximately -55 mV with potassium chloride pipettes, suggesting that this inhibitory postsynaptic potential is primarily mediated by a chloride conductance. In light of previous findings indicating that inhibition in the lateral amygdaloid nucleus arises mostly from local inhibitory neurons, these results suggest that interneurons are synaptically coupled via GABAA receptors. Moreover, the opposite response profiles of interneurons and projection cells to cortical shocks indicate that interneurons play a critical role in regulating the activity of projection cells. The cellular interactions evidenced in the present study suggest that the lateral amygdaloid nucleus is endowed with an inhibitory gating mechanism that regulates information flow through the amygdala.
我们实验室之前的研究表明，外侧杏仁核投射神经元的兴奋性受到GABA介导的抑制性突触后电位和可由突触输入激活的内在电导的严格调控。在此，我们研究了在猫体内细胞内记录的外侧杏仁核中间神经元的突触反应性，以探讨它们在调节投射细胞活动中的作用。中间神经元通过其无棘的树突形态在形态学上得以识别，在生理学上则通过它们对去极化电流脉冲产生高频、非适应性动作电位序列的能力来识别。强度逐渐增加的皮层电刺激在中间神经元和投射细胞中产生了相反的反应模式，中间神经元逐渐变得更加兴奋，而投射细胞则受到更强的抑制。这些皮层诱发的反应模式与中间神经元和投射细胞相对于不同振幅的自发脑电图事件的活动情况相似。只有在最低强度时，两种细胞类型才主要引发兴奋性反应。结果，只有很窄范围的低刺激强度能够触发投射细胞产生动作电位。在两种细胞类型中，最初的皮层诱发兴奋性突触后电位之后都跟着一个超极化，中间神经元的超极化幅度和持续时间明显更低。在中间神经元中，使用醋酸钾电极时超极化在约-72 mV时反转，使用氯化钾电极时在约-55 mV时反转，这表明这种抑制性突触后电位主要由氯离子电导介导。鉴于之前的研究结果表明外侧杏仁核中的抑制主要来自局部抑制性神经元，这些结果表明中间神经元通过GABAA受体进行突触耦合。此外，中间神经元和投射细胞对皮层电刺激的相反反应模式表明，中间神经元在调节投射细胞的活动中起关键作用。本研究中所证明的细胞间相互作用表明，外侧杏仁核具有一种抑制性门控机制，可调节通过杏仁核的信息流。
