Use Multi-Fiber Photometry to Record Neural Activities in Freely-Moving Animals

   |  July 9, 2021
Use Multi-Fiber Photometry to Record Neural Activities in Freely-Moving Animals

The fiber photometry system records changes in the intensity of fluorescence of neurons in specific brain regions to characterize changes in the activity of neuronal populations. It can detect population neurons in free-moving animals for long periods of time, which is helpful to explore the correlation between neuron activity and animal behavior.

After mastering the first two chapters, you will be proficient in recording signals from free-behaving animals using a fiber photometry system. In this article, we will show some real experimental examples that will help inspire your experimental design.

The fiber photometry system used in the experimental case is as follows.

R810 Dual Color Multichannel Fiber Photometry System has two excitation light sources (410nm and 470nm). The 410 nm can be used to reflect the background noise signal, thus ensuring the acquisition of true fluorescence data.

R820 Tri-Color Multichannel Fiber Photometry System has three excitation light sources (410nm , 470nm and 560nm).The system can record signal of green fluorescence indicator like GCaMP and dLight or neurotransmitter probe and red fluorescence indicator like RCaMP, jrGECO1a or neurotransmitter probe.

Key Features and Benefits

Convenient and Efficientel
1) Up to 9 channels, suitable for multiple sites or animals
2) The software integrates data acquisition and analysis modules
3) Setting to start/end the experiment manually or automatically
4) Integrated system, fast connection

Feature-Rich Extensions
1) Supports input and output TTL signals
2) Multiple event markers can be added (external hardware/manual/track ROI tracking)
3) Built-in behavior video recording module, real-time tracking of animal tracks
4) Compatible optogenetics

Data Visualization
1) Preview mode helps to adjust experimental parameters according to test conditions
2) Real-time display of event markers allows direct observation of signal changes
3) Live display of DeltaF/F acquisition to check scale of signal changes during acquisition
4) Analysis module can directly output Df, Z-score analysis results, graphs and heat maps

High Sensitivity
1) Highly sensitive CMOS detector
2) Dual detector +TDM design
3) High stability of LED light source and laptop
4) Equipped with photobleaching device to reduce the autofluorescence of accessories

Some References

Use the Fiber Photometry, DG-projecting SuM neurons were observed to show increased activity and firing frequency in a novel environments

(Ya-Dong Li, et al. nature neuroscience, 2022)

Background and Customer Needs

Adult hippocampal neurogenesis plays an important role in memory and emotional processing. New hippocampal neurons are generated, mature and integrated into existing circuits in the dentate gyrus (DG), and this process is dynamically regulated by the activity of the neural circuits. Current research focuses on neural circuits that regulate certain stages of neurogenesis, such as stem cell division, neural progenitor cell differentiation, or immature neuron survival. However, the effect of new hippocampal neurons modified by neural circuitry on behavioral memory in animals remains unclear.

The research team has already found in previous studies that SuM releases both glutamate and GABA transmitters at DG, which can directly modulate the activity of DG granule cells storing spatial memory and promote spatial memory extraction. Since glutamate and GABA transmitters play an important role in regulating neural development, the group hypothesized that SuM might promote hippocampal neurogenesis and could regulate learning memory and emotion.

Demand of the Research

Previous studies have shown that the increased firing of SuM neurons is in response to environmental and social novelty. The researchers then chose the enriched environment (EE) because EE is a well-established proneurogenic stimulus with a powerful effect on hippocampal neurogenesis. To label SuM neurons projected by DG, they injected RetroAAV-Cre in DG and AAV-DIO-GFP in SuM. EE significantly increased c-fos expression (HC) in DG projection SuM neurons compared with domestic mice. They then recorded the calcium dynamics of DG-projecting SuM neurons by fiber photometry, injecting RetroAAV-Cre into the DG and AAV-DIO-Gcamp7f into the SuM to label DG-projecting SuM neurons.

Results and Effects

Calcium activity in SuM neurons was significantly increased in EE mice compared with controls. These results suggest that DG-projecting SuM neurons are highly responsive to environmental novelty.

Ca2+ signals suggest that – Morphine abstinence reduced excitatory synaptic transmission from amygdala to NAc

(Gui-Ying Zan, et al. Cell Reports, 2021)

Background and Customer Needs

Long-term exposure to opioids is associated with a significant increase in prednisolone (dynorphin)/k-opioid receptor (KORs) signaling in brain reward circuits. Several studies have found that KORs are involved in depression-like behavior induced by opioid withdrawal and that this behavior is associated with reduced dopamine (DA) release in the nucleus accumbens (NAc). Furthermore, the amygdala is a KORs-sensitive glutamatergic afferent brain region, and amygdala neurons also have an important role in regulating DA release in the NAc. However, the molecular mechanisms and neuronal circuits by which KORs regulate this aversive mood associated with opioid withdrawal are currently unknown.

The researchers wanted to confirm that KORs afferent to NAc from amygdala might be involved in opiate-abstinence-induced depressive behavior, and explored the molecular mechanism by which KORs inhibited glutamatergic afferent to NAc from amygdala.

Demand of the Research

Given that morphine abstinence activated KORs and upregulated GLT1 in the amygdala, this raises the possibility that morphine abstinence may induce depressive-like behavior by decreasing DA concentrations in the NAc through kol-dependent and GLT1-mediated inhibition of excitatory synaptic inputs from the amygdala to the NAc. The researchers also found that the frequency of sEPSCs in NAc neurons of morphine abstinence mice was significantly reduced. They then injected AAV9 – CaMKIIa – GCaMP6m into the BLA and inserted optical fibers into the NAc, thereby recording the activity of BLA-NAc projections.

Results and Effects

Ca2+ signals were much lower in morphine abstinence mice compared to controls, which supports the conclusion that morphine abstinence reduces excitatory synaptic transmission from the amygdala to the NAc.

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