Biology subjects

Wu, J.-y.

Publications and source records attributed to Wu, J.-y..

5 recordsLinked to original sources

bioRxiv2026

Improving the detection sensitivity of calcium transients in densely labeled neuronal tissue with pinhole illumination - A low-cost approach

Optical recording from large numbers of neurons is an indispensable technique for studying neuronal ensembles. We use optical sectioning through pinhole illumination to reduce the background fluorescence (F0) and increase the optical signal ({Delta}F/F0) in ex vivo brain slices densely labeled with GCaMP6f, allowing an ordinary fluorescence microscope to capture calcium transients from over 300 individual CA1 neurons - a marked increase compared to ordinary wide field fluorescence illumination. Multiple layers of overlapping neurons can be identified by their locations and the shape in space of their {Delta}F/F0 images. A single pinhole mask was placed at the field stop of a wide field illuminator, and the image of the pinhole was projected onto the tissue by a 20X NA 0.95 water immersion objective (Olympus). This created an illuminated disk with a diameter of [~]200 m and optical sections of hippocampal CA1 pyramidal layer tissue [~]100 m thick. This illumination blocked a large fraction of the F0, which in turn increased the {Delta}F/F0 5-10-fold compared to that of wide field illumination. When putative pyramidal neurons fire sparsely in the brain slice, up to 300 partially superimposed neurons can be identified by their shape and spatial location in the thick ([~]480 m) ex vivo slice in the CA1 area surrounding the pinhole image. The signal-to-noise ratio was adequate even at a low excitation light level of [~]20k photoelectrons per pixel well on the camera, allowing for 3,000 seconds of total recording time without significant bleaching. This pinhole "half confocal" method has created a useful way to sample calcium transient signals in thick tissue with a large population of neurons densely labeled with GCaMP-6f.

neuroscience↗

bioRxiv2026

Restoring hippocampal sharp-wave ripples under glutamate transporter dysfunction

Disruption of glutamate homeostasis is believed to contribute to the early progression of Alzheimers disease (AD) and associated neurodegeneration. Soluble amyloid-{beta} oligomers impair excitatory amino acid transporters (EAATs), reducing glutamate clearance, while also enhancing glutamate release from neurons and astrocytes. Together, these effects produce persistent glutamatergic dysregulation that disrupts synaptic and network function. Here, we asked whether the effects of EAAT attenuation can be mitigated through ion-channel modulation. TBOA, a selective EAAT inhibitor, was used to model early-stage glutamatergic dysregulation. TBOA reduced the local field potential amplitude of hippocampal sharp-wave ripples (SWRs) in mouse hippocampal slices, suggesting that glutamate accumulation disrupts network synchrony. Calcium imaging further showed that TBOA diminished SWR-associated population calcium transients while promoting spontaneous calcium transients in individual neurons, indicating a shift from coordinated population activity toward disorganized cellular activity. KCNQ-channel openers ML213 and ICA-27243 partially restored the TBOA-induced decline in SWR amplitude. In contrast, similar restorative effects were not observed following modulation of other ion channels, including blockade of AMPA and NMDA receptors or HCN/Ih channels, or activation of large-conductance Ca2+-activated K+ (BK) channels and G-protein-activated inwardly rectifying potassium (GIRK) channels. Together, these findings suggest that KCNQ-channel openers may occupy a unique position in mitigating glutamate-related hyperexcitability during early AD-associated network dysfunction.

neuroscience↗

bioRxiv2022

The inhibitory control of traveling waves in cortical networks

Propagating waves of activity can be evoked and can occur spontaneously in vivo and in vitro. We examine the properties of these waves as inhibition varies in a cortical slice and then develop several computational models. We first show that in the slice, inhibition controls the velocity of propagation as well as the magnitude of the local field potential. We introduce a spiking model of sparsely connected excitatory and inhibitory theta neurons which are distributed on a one-dimensional domain and illustrate both evoked and spontaneous waves. The excitatory neurons have an additional spike-frequency adaptation current which limits their maximal activity. We show that increased inhibition slows the waves down and limits the participation of excitatory cells in this spiking network. Decreased inhibition leads to large amplitude faster moving waves similar to those seen in seizures. To gain further insight into the mechanism that control the waves, we then systematically reduce the model to a Wilson-Cowan type network using a mean-field approach. We simulate this network directly and by using numerical continuation to follow traveling waves in a moving coordinate system as we vary the strength and spread of inhibition and the strength of adaptation. We find several types of instability (bifurcations) that lead to the loss of waves and subsequent pattern formation. We approximate the smooth nonlinearity by a step function and obtain expressions for the velocity, wave-width, and stability. Author summaryStimuli and other aspects of neuronal activity are carried across areas in the brain through the concerted activity of recurrently connected neurons. The activity is controlled through negative feedback from both inhibitory neurons and intrinsic currents in the excitatory neurons. Evoked activity often appears in the form of a traveling pulse of activity. In this paper we study the speed, magnitude, and other properteis of these waves as various aspects of the negative feedback are altered. Inhibition enables information to be readily transmitted across distances without the neural activity blowing up into a seizure-like state.

neuroscience↗

bioRxiv2019

Venlafaxine stimulates an MMP-9-dependent increase in excitatory/inhibitory balance in a stress model of depression

Emerging evidence suggests that there is a reduction in overall cortical excitatory to inhibitory balance in major depressive disorder (MDD), which afflicts approximately 14-20% of individuals. Reduced pyramidal cell arborization occurs with stress and MDD, and may diminish excitatory neurotransmission. Enhanced deposition of perineuronal net (PNN) components also occurs with stress. Since parvalbumin-expressing interneurons are the predominant cell population that is enveloped by PNNs, which enhance their ability to release GABA, excess PNN deposition likely increases pyramidal cell inhibition. In the present study we investigate the potential for matrix metalloprotease-9 (MMP-9), an endopeptidase secreted in response to neuronal activity, to contribute to the antidepressant efficacy of venlafaxine, a serotonin/norepinephrine reuptake inhibitor. Chronic venlafaxine increases MMP-9 levels in murine cortex, and increases both pyramidal cell arborization and PSD-95 expression in the cortex of wild-type but not MMP-9 null mice. We have previously shown that venlafaxine reduces PNN deposition and increases the power of ex vivo gamma oscillations in conventionally-housed mice. Gamma power is increased with pyramidal cell disinhibition and with remission from MDD. Herein we observe that PNN expression is increased in a corticosterone-induced stress model of disease and reduced by venlafaxine. As compared to mice that receive concurrent venlafaxine, corticosterone treated mice also display reduced ex vivo gamma power and impaired working memory. Autopsy-derived prefrontal cortex samples show elevated MMP-9 levels in anti-depressant treated MDD patients as compared to controls. These preclinical and postmortem findings highlight a link between extracellular matrix regulation and MDD.

neuroscience↗

bioRxiv2018

Measurements of Subthreshold and Fast Population Neuronal Activity with Genetically Encoded Calcium Indicator GCaMP-6f

GCaMP-6f is among the best calcium indicators and has been widely used for monitoring neuronal activity in the brain. Applications are at cellular level (calcium transients of action potentials) or population activity (fluorimetry) during network events. Two important issues remain less explored: 1) Is GCaMP-6f signal sensitive enough for detecting subthreshold activity, similar to the sensitivity of local field potential (LFP)? 2) Is the GCaMP-6f signal fast enough for detecting network oscillations seen in LFP? Here the two issues are explored in a number of network events including hippocampus sharp waves (SWs), carbachol induced theta oscillations, interictal-like spikes and neuronal response evoked by high frequency stimuli. SWs are a typical network event with the majority of neurons receiving subthreshold excitatory or inhibitory synaptic input without firing action potentials. The excitatory/inhibitory post synaptic potentials (EPSP/IPSP) in the neuropil become detectable in local field potential (LFP) signals. We compare simultaneously recorded LFP and optical recording of GCaMP-6f fluorescent signals in Thy1-GCaMP-6f mice hippocampal slices. We found that the occurrence of SWs produces a clear population GCaMP-6f signal of 0.3% dF/F. This population GCaMP-6f signal correlated well with the LFP, albeit a delay of ~50 ms was observed. The population GCaMP-6f signal follows well with the 20 Hz population activity evoked by electric stimuli, while activity up to 40 Hz was detected with reduced amplitude. GCaMP-6f and LFP signals showed a large amplitude discrepancy. The amplitude of GCaMP increased ~1000 times from SW to carbachol induced theta burst, while the LFP changed less than 10 times. Our results suggested that population GCaMP-6f signals may become a sensitive tool for detecting network activity, especially for that with low LFP amplitude during elevated spiking rate but asynchronized events. GCaMP signal is fast enough for monitoring theta and beta oscillations (<25Hz) in the neuronal population. Faster calcium indicators (e.g., GCaMP-7) may improve the frequency response property for detecting gamma band oscillations. In addition, population GCaMP recordings are non-contact and free from stimulation artifacts. These features may be useful for high throughput recordings and applications sensitive to stimulus artifact, e.g., monitoring response during continuous stimulations.

neuroscience↗