Federated Department of Biological Sciences, New Jersey Institute of Technology and Rutgers University-Newark, Newark, NJ 07102.
Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, NJ 07102.
eNeuro. 2021 Nov 22;8(6). doi: 10.1523/ENEURO.0351-21.2021. Print 2021 Nov-Dec.
Postsynaptic responses depend on input patterns as well as short-term synaptic plasticity, summation, and postsynaptic membrane properties, but the interactions of those dynamics with realistic input patterns are not well understood. We recorded the responses of the two pyloric dilator (PD) muscles, and , that are innervated by and receive identical periodic bursting input from the same two motor neurons in the lobster and showed quantitative differences in membrane nonlinearities and synaptic summation. At a short timescale, responses in both muscles were dominated by facilitation, albeit with different frequency and time dependence. Realistic burst stimulations revealed more substantial differences. Across bursts, showed transient depression, whereas showed transient facilitation. Steady-state responses to bursting input also differed substantially. Neither muscle had a monotonic dependence on frequency, but showed particularly pronounced bandpass filtering. was sensitive to changes in both burst frequency and intra-burst spike frequency, whereas, despite its much slower responses, was largely insensitive to changes in burst frequency. was sensitive to both burst duration and number of spikes per burst, whereas was sensitive only to the former parameter. Neither muscle showed consistent sensitivity to changes in the overall spike interval structure, but was surprisingly sensitive to changes in the first intervals in each burst, a parameter known to be regulated by dopamine (DA) modulation of spike propagation of the presynaptic axon. These findings highlight how seemingly minor circuit output changes mediated by neuromodulation could be read out differentially at the two synapses.
突触后反应不仅取决于输入模式，还取决于短期突触可塑性、总和和突触后膜特性，但这些动力学与现实输入模式的相互作用还不是很清楚。我们记录了两个贲门扩张肌（PD）的反应， 和 ，它们由相同的两个运动神经元支配，并接收相同的周期性爆发输入，显示出膜非线性和突触总和的定量差异。在短时间尺度上，两种肌肉的反应都以易化为主，尽管易化的频率和时间依赖性不同。现实的爆发刺激显示出更显著的差异。在爆发期间， 表现出短暂的抑制，而 表现出短暂的易化。对爆发输入的稳态反应也有很大的不同。两种肌肉都没有单调依赖于频率，但 表现出特别明显的带通滤波。 对爆发频率和爆发内尖峰频率的变化都很敏感，而 尽管其反应较慢，但对爆发频率的变化基本不敏感。 对爆发持续时间和每个爆发中的尖峰数都很敏感，而 只对前一个参数敏感。两种肌肉对整体尖峰间隔结构的变化都没有一致的敏感性，但 对每个爆发中的第一个间隔的变化非常敏感，这是一个已知由多巴胺（DA）调制的突触前轴突尖峰传播来调节的参数。这些发现强调了看似微小的电路输出变化如何通过神经调制在两个突触处被差异读出。
