The Patch-Clamp Method
The patch clamp method provides a high-resolution method for observing the function of a single ion channel in various normal and pathological cell types and is the standard for the electrophysiological characterization of a single neuron. By combining the high-resolution electrophysiological recording information of the patch clamp method with modern molecular biotechnology, we can further understand the gene expression and protein structure of ion channels. These advances provide unlimited possibilities for the neuroscience research process. For example, nerve cells, glial cells, signal transduction, synaptic transmission, as well as epilepsy, brain and spinal cord injuries all can be studied by patch clamp technology.
Patch-Clamp Principles and Advantages
Patch clamp technology uses a glass electrode to achieve electrical access inside the neuron membrane, to achieve low-noise, high-time resolution recording, and neuron electrical signal operation. This process is performed by determining the physical contact between the electrode and the excitatory cell membrane. Once the contact is confirmed, it applies a slight negative pressure on the pipette to draw the membrane patch into the electrode and achieve mechanical stability and high impedance sealing.
Fig.1 Basic patch clamp technique mode. (Annecchino, 2018)
- Less trauma to cells
- High-resistance sealing minimizes leakage current and makes low-noise recording possible
- Wide applicability to cell types
Applications of Patch Clamp
- In vivo application of patch clamp
On the basis of commercial two-photon microscopes, it is combined with patch clamp technology to produce image-guided biopsy technology. It can be used in patches to target cortical PV-positive neurons, cortical camkla-positive neurons, and wild-type mouse cortical pyramidal neurons, and astrocytes. These findings successfully linked single neuron activity with advanced brain functions. Figure 3 shows the record of cortical PV-positive cells.
Fig.2 Two-channel image of cortical PV-positive neurons obtained using imagepatcher. (Suk, 2019)
- In vitro application of patch clamp
Differential interference contrast (DIC) optical technology is another major advancement in clamping the patch on the brain slice. The improved imaging quality provided by DIC-based microscopes enables neurons on mammalian brain slices to target somatic cells and dendrites. This has become a standard method for studying neurons in brain slices. Recently, with the emergence of genetically engineered mouse models, cell type-specific fluorescent labeling (applicable to transgenic mice) and fluorescence imaging (surface fluorescence microscopy) have been successfully combined with patch clamps to study genetically defined neuron categories in vitro.
Fig.3 In vitro automatic vision guided whole cell recording. (Annecchino, 2018)
The nervous system is the most complex organ in the human body. The development of automatic patch-clamp technology can carry out high-throughput and high-content research on the neural relevance of neurological diseases in the body to determine the cellular, molecular and pharmacological pathways, and help clarify the initiation and progress of specific diseases.
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References
- Annecchino, L.A.; Schultz, S.R. Progress in automating patch clamp cellular physiology. Brain and neuroscience advance. 2018, 2: 2398212818776561.
- Suk, H.J.; et al. Advances in the automation of whole-cell patch clamp technology. Journal of neuroscience methods. 2019, 326: 108357.
