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Melanopsin for precise optogenetic activation of astrocyte-neuron networks
摘要： Optogenetics has been widely expanded to enhance or suppress neuronal activity and it has been recently applied to glial cells. Here, we have used a new approach based on selective expression of melanopsin, a G-protein-coupled photopigment, in astrocytes to trigger Ca2+ signaling. Using the genetically encoded Ca2+ indicator GCaMP6f and two-photon imaging, we show that melanopsin is both competent to stimulate robust IP3-dependent Ca2+ signals in astrocyte fine processes, and to evoke an ATP/Adenosine-dependent transient boost of hippocampal excitatory synaptic transmission. Additionally, under low-frequency light stimulation conditions, melanopsin-transfected astrocytes can trigger long-term synaptic changes. In vivo, melanopsin-astrocyte activation enhances episodic-like memory, suggesting melanopsin as an optical tool that could recapitulate the wide range of regulatory actions of astrocytes on neuronal networks in behaving animals. These results describe a novel approach using melanopsin as a precise trigger for astrocytes that mimics their endogenous G-protein signaling pathways, and present melanopsin as a valuable optical tool for neuron–glia studies.
关键词： neuron–glia interactions,synaptic plasticity,optogenetics,astrocytes,melanopsin
更新于2025-09-23 15:23:52
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Artificial association of memory events by optogenetic stimulation of hippocampal CA3 cell ensembles
摘要： Previous gain-of-function studies using an optogenetic technique showed that manipulation of the hippocampal dentate gyrus or CA1 cell ensembles is important for memory reactivation and to generate synthetic or false memory. However, gain-of-function study manipulating CA3 cell ensembles has not been reported. The CA3 area of the hippocampus comprises a recurrent excitatory circuit, which is thought to be important for the generation of associations among the stored information within one brain region. We investigated whether the coincident firing of cell ensembles in one brain region, hippocampal CA3, associates distinct events. CA3 cell ensembles responding to context exploration and during contextual fear conditioning were labeled with channelrhodopsin-2 (ChR2)-mCherry. The synchronous activation of these ensembles induced freezing behavior in mice in a neutral context, in which a foot shock had never been delivered. The recall of this artificial associative fear memory was context specific. In vivo electrophysiological recordings showed that 20-Hz optical stimulation of ChR2-mCherry-expressing CA3 neurons, which is the same stimulation protocol used in behavioral experiment, induced long-term potentiation at CA3-CA3 synapses. Altogether, these results demonstrate that the synchronous activation of ensembles in one brain region, CA3 of the hippocampus, is sufficient for the association of distinct events. The results of our electrophysiology potentially suggest that this artificial association of memory events might be induced by the strengthening of synaptic efficacy between CA3 ensembles via recurrent circuit.
关键词： CA3,Synaptic plasticity,Artificial association,Optogenetics,Recurrent circuit,Long-term potentiation (LTP),Hippocampus
更新于2025-09-23 15:22:29
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[Handbook of Behavioral Neuroscience] Handbook of in Vivo Neural Plasticity Techniques Volume 28 || Functional MRI of Synaptic Plasticity
摘要： Functional magnetic resonance imaging (fMRI) utilizes MRI technology to indirectly measure neuronal activity. The most common form of fMRI uses the blood oxygen level dependent (BOLD) contrast. It relies on the brain’s ability to locally modulate blood flow and volume to satisfy the increased energetic needs during neuronal activation. The relationship between increased local neural activity and changes in cerebral blood flow (CBF) is known as neurovascular coupling (or functional hyperemia). The correlation between BOLD signals and concomitantly recorded electrophysiological measures is well established, although the exact molecular mechanism remains unclear and its homogeneity throughout brain regions debated. Functional MRI allows imaging brain activations with a spatial resolution as low as a few hundreds of microns and with a temporal resolution of seconds.
关键词： Hippocampus,BOLD contrast,Synaptic Plasticity,Neurovascular coupling,Functional MRI
更新于2025-09-23 15:21:21
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Dynamic Color‐Switching of Plasmonic Nanoparticle Films
摘要： Single‐housed stress elicits a range of social isolation‐related behavioral and neurobiological abnormalities. To investigate single housing‐induced behavioral changes and sex differences on stress outcomes, we examined single‐housed stress‐induced learning and memory impairment, depression‐like behaviors, neuroplasticity abnormalities and underlying mechanism. The results showed that male and female mice socially isolated for 8 weeks had significantly decreased memory acquisition, as demonstrated in the learning curve of the Morris water maze task. Memory consolidation and retrieval were also decreased in both the single‐housed male and female mice. These findings were corroborated further by the two classical animal models, Y‐maze and novel object recognition tests, as demonstrated by reduced spontaneous alternation and recognition index in both sexes of single‐housed mice. Subsequent studies suggested that single‐housed male mice exhibited increased immobility time in both the forced swim and tail suspension tests, while the female mice only exhibited increased immobility time in the tail suspension test. Moreover, single‐housed stress significantly decreased the apical and basal branch points, dendritic length, and spine density in the CA1 of hippocampal neurons in both male and female mice. These effects were consistent with decreased neuroplasticity and neuroprotective‐related molecules such as synaptophysin, PSD95, PKA, pCREB and BDNF expression. These findings suggest that loss of neuronal remodeling and neuroprotective mechanisms due to single housing are involved in behavioral changes in both male and female mice. The results provide further evidence that neuroplasticity‐related signaling plays a crucial role in isolation‐induced effects on neuropsychiatric behavioral deficits in both sexes.
关键词： neuroplasticity,synaptic plasticity‐associated proteins,depression,cognition,single housing stress
更新于2025-09-11 14:15:04