GABAergic inhibition reduces the impact of synaptic excitation on somatic excitation

In Vivo Whole-Cell Patch-Clamp Methods: Recent Technical Progress and Future Perspectives

Brain functions are fundamental for the survival of organisms, and they are supported by neural circuits consisting of a variety of neurons. To investigate the function of neurons at the single-cell level, researchers often use whole-cell patch-clamp recording techniques. These techniques enable us to record membrane potentials (including action potentials) of individual neurons of not only anesthetized but also actively behaving animals. This whole-cell recording method enables us to reveal how neuronal activities support brain function at the single-cell level. In this review, we introduce previous studies using in vivo patch-clamp recording techniques and recent findings primarily regarding neuronal activities in the hippocampus for behavioral function. We further discuss how we can bridge the gap between electrophysiology and biochemistry.

Functional Multiple-Spine Calcium Imaging from Brain Slices

Most excitatory inputs arrive at dendritic spines in a postsynaptic neuron. To understand dendritic information processing, it is critical to scrutinize the spatiotemporal dynamics of synaptic inputs along dendrites. This protocol combines spinning-disk confocal imaging with whole-cell patch-clamp recording to perform wide-field, high-speed optical recording of synaptic inputs in a neuron loaded with a calcium indicator in ex vivo cultured networks. Our protocol enables simultaneous detection of synaptic inputs as calcium signals from hundreds of spines in multiple dendritic branches.

For complete details on the use and execution of this protocol, please refer to Takahashi et al. (2012, 2016), Kobayashi et al. (2019), and Ishikawa and Ikegaya (2020).

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Simultaneous calcium imaging of synaptic activity from hundreds of spines in vitro

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Whole-cell voltage clamping for dye loading and signal improvement

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Photobleaching-free and photodamage-free imaging of synaptic activity by spinning-disk confocal system

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A modified median filter for effective denoising of optical signals

Locally sequential synaptic reactivation during hippocampal ripples

The sequential reactivation of memory-relevant neuronal ensembles during hippocampal sharp-wave (SW) ripple oscillations reflects cognitive processing. However, how a downstream neuron decodes this spatiotemporally organized activity remains unexplored. Using subcellular calcium imaging from CA1 pyramidal neurons in ex vivo hippocampal networks, we discovered that neighboring spines are activated serially along dendrites toward or away from cell bodies. Sequential spine activity was engaged repeatedly in different SWs in a complex manner. In a single SW event, multiple sequences appeared discretely in dendritic trees, but overall, sequences occurred preferentially in some dendritic branches. Thus, sequential replays of multineuronal spikes are distributed across several compartmentalized dendritic foci of a postsynaptic neuron, with their spatiotemporal features preserved.