Oswald Anne-Marie M, Lewis John E, Maler Leonard
Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.
J Neurophysiol. 2002 May;87(5):2450-63. doi: 10.1152/jn.00711.2001.
Descending feedback is a common feature of sensory systems. Characterizing synaptic plasticity in feedback inputs is essential for delineating the role of feedback in sensory processing. In this study, we demonstrate that multiple interacting processes underlie the dynamics of synaptic potentiation in one such sensory feedback pathway. We use field recording and modeling to investigate the interaction between the transient high-magnitude potentiation (200-300%) elicited during tetanic stimulation of the feedback pathway and the lower magnitude posttetanic potentiation (PTP; ~30%) that slowly decays on cessation of the tetanus. The amplitude of the observed transient potentiation is graded with stimulus frequency. In contrast, the induction of PTP has a stimulus frequency threshold between 1 and 5 Hz, and its amplitude is independent of stimulus frequency. We suggest that the threshold for PTP induction may be linked to a minimum level of sustained potentiation (MSP) during repetitive trains of stimuli. We have developed a novel model that describes the interaction between the transient plasticity observed during train stimulation and the generation of PTP. The model combines a multiplicative, facilitation-depression-type (FD) model that describes the transient plasticity, with an enzymatic network that describes the dynamics of PTP. The model links transient plasticity to PTP through an input term that reflects MSP. The stratum fibrosum-pyramidal cell (StF-PC) synapse investigated in this study is the terminus of a feedback pathway to the electrosensory lateral line lobe (ELL) of a weakly electric gymnotiform fish. Dynamic plasticity at the StF-PC synapse may contribute to the putative role of this feedback pathway as a sensory searchlight.
下行反馈是感觉系统的一个常见特征。表征反馈输入中的突触可塑性对于阐明反馈在感觉处理中的作用至关重要。在本研究中，我们证明了多个相互作用的过程是一种这样的感觉反馈通路中突触增强动力学的基础。我们使用场记录和建模来研究在反馈通路的强直刺激期间引发的瞬态高强度增强（200 - 300%）与在强直停止后缓慢衰减的低强度强直后增强（PTP；约30%）之间的相互作用。观察到的瞬态增强的幅度随刺激频率分级。相比之下，PTP的诱导具有1至5赫兹之间的刺激频率阈值，并且其幅度与刺激频率无关。我们认为PTP诱导的阈值可能与重复刺激序列期间的最低持续增强水平（MSP）相关。我们开发了一种新颖的模型，该模型描述了在序列刺激期间观察到的瞬态可塑性与PTP产生之间的相互作用。该模型将描述瞬态可塑性的乘法、易化 - 抑制型（FD）模型与描述PTP动力学的酶网络相结合。该模型通过反映MSP的输入项将瞬态可塑性与PTP联系起来。在本研究中研究的纤维层 - 锥体细胞（StF - PC）突触是弱电裸背电鳗形鱼类的电感觉侧线叶（ELL）的反馈通路的终点。StF - PC突触处的动态可塑性可能有助于该反馈通路作为感觉探照灯的假定作用。
