Establishing a Whole-Cell Configuration for Two-Photon Calcium Imaging of Brain Slices
JoVE Encyclopedia of Experiments
Neuroscience
0 views • 3:44 min • July 8th, 2025
Take a stimulation pipette containing red calcium-insensitive fluorophores in artificial cerebrospinal fluid, or ACSF.
Position the pipette near the target neuron in a hippocampal slice.
Place a patch pipette with a recording electrode bathed in an electrolyte containing red calcium-insensitive and green calcium indicator fluorophores near the target.
Apply constant positive pressure to briefly disturb the tissue surface, indicating proximity to the target.
As the dimple forms on the neuronal membrane, release the pressure to form a seal.
Apply negative pressure to tighten the seal.
Stabilize the membrane potential at a constant negative voltage.
Continue with negative pressure to break the membrane, allowing the fluorophore-containing electrolytes to spread within the neuron.
Visualize the red fluorescence of the target dendritic spine and align the stimulation pipette near it.
Apply electrical pulses to open the calcium channels.
Use two-photon microscopy to visualize transient changes in calcium levels as indicated by green fluorescence.
In this step, transfer a hippocampal slice to a bath under the objective of a laser-scanning two-photon microscope. Continuously perfuse the bath with oxygenated ACSF normal. Then, use Infrared Differential Interference Contrast Microscopy to locate a cell of interest using its size, shape, and position.
After that, fill a stimulating pipette with an ACSF normal solution containing the red fluorophore. Lower it on top of the slice so that the tip is in the same region as the cell of interest. Following that, fill the patch pipette with patch solution, and attach it to the head stage. Set it over the slice so that its tip is directly above the cell of interest.
Subsequently, fit a syringe into the three-way stopcock and connect it to the patch pipette through a plastic tube. Inject constant positive pressure into the patch pipette and keep the stopcock in closed position. Lower the patch pipette until it is right on top of the targeted cell. Upon making contact with the cell membrane, remove the pressure by turning the stopcock into the open position.
Then, apply a slight negative pressure to the patch pipette using an empty syringe fitted into the stopcock until the pipette resistance reaches 1 giga ohm. In the membrane test window of the data acquisition software, clamp the cell at negative 60 millivolts. Continue applying negative pressure until the pipette resistance drops and the whole cell configuration is achieved.
To record dendritic calcium transients induced by electrical stimulation, locate a dendrite of interest using the red fluorescent signal. Set the stimulating pipette on the surface of the slice above the dendrite of interest. Slowly lower the stimulation pipette 10 to 15 micrometers from the dendrite, minimizing movement to avoid disturbing the whole-cell configuration.
Overview
This article describes a method for visualizing calcium transients in hippocampal neurons using two-photon microscopy. The technique involves the use of stimulation and patch pipettes to manipulate and record from target neurons.
Key Study Components
Area of Science
- Neuroscience
- Electrophysiology
- Imaging Techniques
Background
- Calcium signaling is crucial for neuronal function.
- Two-photon microscopy allows for high-resolution imaging of live neurons.
- Understanding calcium dynamics can provide insights into neuronal behavior.
- Patch-clamp techniques are essential for studying cellular properties.
Purpose of Study
- To visualize calcium transients in dendritic spines of hippocampal neurons.
- To demonstrate the use of combined electrophysiological and imaging techniques.
- To enhance understanding of synaptic activity and neuronal signaling.
Methods Used
- Preparation of hippocampal slices for experimentation.
- Use of stimulation and patch pipettes for targeted manipulation.
- Application of two-photon microscopy for imaging calcium levels.
- Recording of electrical activity and calcium transients in neurons.
Main Results
- Successful visualization of calcium transients in response to electrical stimulation.
- Demonstration of the effectiveness of the combined techniques.
- Identification of specific dendritic spines involved in synaptic activity.
- Insights into the dynamics of calcium signaling in neurons.
Conclusions
- The method provides a powerful tool for studying neuronal calcium dynamics.
- Combining electrophysiology with imaging enhances our understanding of neuronal function.
- This approach can be applied to various studies in neuroscience.
Frequently Asked Questions
Executive Industry Relevance
Whole-cell patch-clamp combined with two-photon calcium imaging enables precise interrogation of neuronal calcium dynamics in brain slices, supporting mechanistic de-risking in early CNS drug discovery. This approach provides quantitative, high-resolution data on synaptic function and signaling, informing target validation and pathway analysis. Its integration into discovery workflows enhances predictive confidence for neuropharmacological portfolios.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables direct measurement of neuronal calcium transients for functional target validation.
- Supports mechanistic de-risking by clarifying synaptic signaling pathways.
- Provides quantitative data to inform go/no-go decisions in CNS target portfolios.
Screening & Assay Development
- Establishes validated brain slice systems for downstream compound screening.
- Delivers reproducible, quantitative readouts of calcium signaling for assay standardization.
- Facilitates reliable evaluation of candidate molecules affecting neuronal excitability.
Translational & Preclinical Research
- Aligns in vitro neuronal activity with disease-relevant synaptic biomarkers.
- Supports continuity from mechanistic discovery to preclinical validation in CNS models.
- Enables risk-adjusted advancement of neuroactive compounds based on functional outputs.
Pipeline & Workflow Integration
This method fits at the intersection of early discovery and preclinical research, bridging mechanistic studies and translational validation in CNS drug development.
- Discovery Biology: Provides direct evidence for hypothesis testing of neuronal signaling mechanisms.
- Screening: Offers quantitative, reproducible calcium imaging outputs for assay readiness.
- Analytics: Enables statistical comparison of synaptic responses under different conditions.
- Translational Research: Connects in vitro findings to disease-relevant neuronal activity patterns.
- Enterprise Reuse: Serves as a reusable platform for diverse CNS target and pathway investigations.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in CNS target validation.
- Operational Value: Standardizes and scales high-resolution neuronal assays for cross-project use.
- Strategic Value: Improves portfolio triage and capital allocation by providing robust functional data.
- Portfolio Impact: Enables risk-adjusted prioritization of neuropharmacological assets.
Implementation Considerations
- Requires expertise in electrophysiology and advanced imaging techniques.
- Demands access to two-photon microscopy and patch-clamp instrumentation.
- Necessitates rigorous cross-team standardization for reproducibility.
- May require adaptation for different neuronal subtypes or brain regions.
- Dependent on tissue quality and fluorophore performance for optimal results.
Biopharma FAQs
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Last updated: 29 August 2026