Boussa Sofiane, Pasquier Jennifer, Leboulenger François, Faure Alain, Foll Frank Le
UPRES-EA, University of Le Havre, France.
J Physiol Paris. 2010 Jan-Mar;104(1-2):99-106. doi: 10.1016/j.jphysparis.2009.11.008. Epub 2009 Nov 10.
Excitable cells are connected via electrical and chemical synapses to form a complex plastic network that transmit and modify action potential trains. In vivo and in vitro studies suggest that powerful type A GABAergic self-innervations, known as autapses, play a central role in the shaping of spike discharges. Herein, we have investigated the effects of artificial autaptic activity on action potential firing in cultured hypophyseal neuroendocrine melanotrope cells removed from any synaptic input. Type A autaptic conductances were introduced by using a dedicated dynamic-clamp device, based on a digital signal processor. The results indicate that cells grafted with autaptic dynamic-clamp are subjected to a modulation of both evoked firing and artificial GABA(A)-currents. The autaptic feedback reduced the action potentials amplitude, decreasing both the overshoot and the after-hyperpolarization potential (AHP). In return, the reduced voltage changes diminished the autaptic current amplitudes. The overall effect was a decrease of the cell firing rate. The introduction of a variable autaptic delay strongly altered the cell responses. Under certain conditions, the artificial autaptic current formed an additional component of the AHP which was markedly augmented. This action resulted in a stabilization of the action potential train leading to a more regular firing. In conclusion, it appeared that the autaptic feedback was very dependent on functional parameters such as the autaptic distance. Further investigations are in progress to complete our model, taking the autaptic plasticity into account.
可兴奋细胞通过电突触和化学突触相连，形成一个复杂的可塑性网络，该网络可传递和修改动作电位序列。体内和体外研究表明，强大的A型γ-氨基丁酸能自神经支配（即自突触）在动作电位发放的形成中起核心作用。在此，我们研究了人工自突触活动对从任何突触输入中分离出来的培养垂体神经内分泌黑素细胞动作电位发放的影响。基于数字信号处理器的专用动态钳位装置引入了A型自突触电导。结果表明，移植了自突触动态钳位的细胞的诱发发放和人工γ-氨基丁酸A电流均受到调制。自突触反馈降低了动作电位幅度，减小了超射和超极化后电位（AHP）。作为回报，电压变化的减小降低了自突触电流幅度。总体效果是细胞发放率降低。引入可变的自突触延迟强烈改变了细胞反应。在某些条件下，人工自突触电流形成了AHP的一个额外成分，该成分明显增强。这一作用导致动作电位序列的稳定，从而导致更规则的发放。总之，自突触反馈似乎非常依赖于诸如自突触距离等功能参数。考虑到自突触可塑性，正在进行进一步研究以完善我们 的模型。
