Institute for Neurophysiology and Cellular Biophysics, University Medical Center Göttingen, 37073, Göttingen, Germany.
Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073, Göttingen, Germany.
Sci Rep. 2021 Jul 9;11(1):14258. doi: 10.1038/s41598-021-93677-9.
Olfactory sensing is generally organized into groups of similarly sensing olfactory receptor neurons converging into their corresponding glomerulus, which is thought to behave as a uniform functional unit. It is however unclear to which degree axons within a glomerulus show identical activity, how many converge into a glomerulus, and to answer these questions, how it is possible to visually separate them in live imaging. Here we investigate activity of olfactory receptor neurons and their axon terminals throughout olfactory glomeruli using electrophysiological recordings and rapid 4D calcium imaging. While single olfactory receptor neurons responsive to the same odor stimulus show a diversity of responses in terms of sensitivity and spontaneous firing rate on the level of the somata, their pre-synaptic calcium activity in the glomerulus is homogeneous. In addition, we could not observe the correlated spontaneous calcium activity that is found on the post-synaptic side throughout mitral cell dendrites and has been used in activity correlation imaging. However, it is possible to induce spatio-temporal presynaptic response inhomogeneities by applying trains of olfactory stimuli with varying amino acid concentrations. Automated region-of-interest detection and correlation analysis then visually distinguishes at least two axon subgroups per glomerulus that differ in odor sensitivity.
嗅觉感知通常被组织成群集的相似的嗅觉受体神经元，这些神经元汇聚到它们相应的嗅球小球，这些嗅球小球被认为是作为一个统一的功能单位发挥作用。然而，嗅球小球内的轴突在多大程度上表现出相同的活动，有多少个轴突汇聚到一个嗅球小球，以及为了回答这些问题，如何在活体成像中对它们进行视觉分离，这些问题目前还不清楚。在这里，我们使用电生理记录和快速的 4D 钙成像技术，研究了整个嗅觉小球中嗅觉受体神经元及其轴突末梢的活动。虽然对同一气味刺激有反应的单个嗅觉受体神经元在体细胞水平上的敏感性和自发放电率方面表现出多样性的反应，但它们在嗅球小球中的前突触钙活动是同质的。此外，我们无法观察到在整个僧帽细胞树突上发现的、在突触后侧存在的相关自发钙活动，而这种钙活动已经被用于活动相关成像。然而，通过应用具有不同氨基酸浓度的嗅刺激序列，可以诱导时空前突触反应的不均匀性。然后，自动感兴趣区域检测和相关分析可以在每个嗅球小球中至少区分出两个在气味敏感性上不同的轴突亚群。
