Name: registration of calcium transients in mouse neuromuscular junction with high temporal resolution using confocal microscopy
Uploaded: 2021-12-01T14:00:00
Description: Watch this Scientific Journal Video about Registration of Calcium Transients in Mouse Neuromuscular Junction with High Temporal Resolution using Confocal Microscopy at JoVE.com

Fluorescence studies of this work were carried out with the financial support of the Russian Science Foundation Grant (project No. 19-15-00329). The method was developed under financing from the government assignment for FRC Kazan Scientific Center of RAS &#1040;&#1040;&#1040;&#1040;-&#1040;18-118022790083-9. The research was developed with the use of the equipment of the Federal Research Center &#34;Kazan Scientific Center of RAS&#34;. The authors would like to thank Dr. Victor I. Ilyin for critical reading of this manuscript.

Experiments were performed on isolated nerve-muscle preparations of levator auris longus (m. LAL) from the Mice BALB/C (20-23 g, 2-3 months old)41. The experimental procedures were performed in accordance with the guidelines for the use of laboratory animals of the Kazan Federal University and the Kazan Medical University, in compliance with the NIH Guide for the Care and Use of Laboratory Animals. The experimental protocol met the requirements of the European Communities Council Directiv...

The method for loading Ca2+-sensitive dye into mouse nerve endings through the nerve stump and for registering a fast calcium transient using a confocal microscope is presented in this article. As a result of the implementation of this loading method, most of the synapses located close to the nerve stump had a sufficient level of fluorescence to enable registration of the entry of calcium into the nerve endings in response to low-frequency stimulation of the motor nerve.
Unlike the ...

The problem of measuring fast calcium waves in excitable cells is one of the most important and challenging aspects of studying signal transmission in the central and peripheral nervous systems. Calcium ions play an important role in triggering neurotransmitter release, synaptic plasticity, and modulation of the activity of various intracellular proteins1,2,3,4,5. Studying calcium signaling is also important for finding ways to treat neurodegenerative diseases6. To measure changes in the calcium levels, fluorescent calcium-sensitive dyes are commonly used, and changes in their fluorescence level are analyzed7,8,9.
Loading of calcium dyes into cells can be achieved in different ways. Predominantly, cell-permeant dyes are used10,11. However, in such a case, it is not only difficult to control the concentration of a dye inside the cell, but it is also hard to select target cells for loading. This method is not applicable for studying peripheral nerve endings since the dye enters postsynaptic cells. Instead, cell impermeant dyes are more suitable for such preparations. In this case, the dyes are delivered to the cells by microinjection or through a patch pipette12,13,14. There is also a method of loading through a nerve stump. The latter method is most suitable for neuromuscular junction preparations15,16,17,18,19,20. It allows performing staining for only cells of interest. Although this method does not provide an accurate evaluation of the concentration of the dye in the target cell, the concentration can be estimated approximately by comparing the level of fluorescence of the cells at rest in solutions with a known concentration of calcium21. In this study, a modification of this method applied to synapses of mammals is presented.
Calcium entry during the depolarizing phase of the action potential is a fast process, especially in the neuromuscular junction; therefore, for its registration, appropriate equipment is required1. A recent study using a voltage-sensitive fluorescent dye demonstrated that the duration of the action potential in the peripheral synapse of a mouse is approximately 300 &#181;s22. Calcium transient, evaluated using calcium-sensitive dyes in the peripheral synapses of the frog, has a longer duration: the rise time is about 2-6 ms and the decay time is about 30-90 ms, depending on the calcium dye used23,24. To measure fast processes with the help of fluorescent dyes, CCD or CMOS cameras are generally used, with fast and sensitive CCD matrices. However, these cameras have the disadvantage of low resolution, limited by the size of the sensitive elements of the matrix25,26,27,28. The fastest cameras with sufficient sensitivity to record both action potentials and calcium transients in response to low frequency stimulation of cells have a scanning frequency of 2,000 Hz, and a matrix with a dimension of 80 x 8029. To obtain signals with a higher spatial resolution, confocal microscopy is used, especially if it is necessary to assess some volumetric changes in the signal30,31,32. But it should be kept in mind that confocal microscopy has a high scanning speed in line scan mode, but there are still significant limitations on the speed of recordings of fast processes when building a spatial image33. There are confocal microscopes based on rotating Nipkow disks (slit-scanning microscopy) and Multipoint-Array Scanners, which have a higher scanning speed. At the same time, they are inferior to the classical confocal microscopes in confocal image filtering (pinholes crosstalk for microscopes with a Nipkow disk)32,34,35. Confocal imaging with resonance scanning can also provide a high spatio-temporal resolution required for high temporal measurements36. However, take into account that the registration of weak fluorescent responses at a high scanning speed when using resonance scanners requires highly sensitive detectors such as hybrid detectors36.
This article presents a method for increasing the temporal resolution of signals recorded with the Laser Scanning Confocal Microscopy (LSCM) while maintaining the spatial resolution37. The current method is a further development of the methods described earlier and transferred to the LSCM platform38,39,40. This approach does not require changes in the microscope hardware and is based on the application of an algorithm for recording periodically evoked fluorescent signals with a time shift relative to the moment of stimulation.

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			<td>Capillary Glass</td>
			<td>Clark Electromedical instruments, UK</td>
			<td>GC150-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal and multiphoton microscope system Leica TCS SP5 MP</td>
			<td>Leica Microsystems , Heidelberg, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Flaming/Brown Micropipette Puller P 97</td>
			<td>Sutter Instrument, USA</td>
			<td>P-97</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow regulator</td>
			<td>KD Medical GmbH Hospital Products, Germany</td>
			<td>KD REG</td>
			<td>Disposable infusion set with Flow regulator</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma-Aldrich, USA</td>
			<td>H0887</td>
			<td>100mL</td>
		</tr>
		<tr>
			<td>Illumination system Leica CLS 150X</td>
			<td>Leica Microsystems, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ImageJ</td>
			<td>National Institutes of Health, USA</td>
			<td></td>
			<td>http://rsb.info.nih.gov/ij/download.html</td>
		</tr>
		<tr>
			<td>Las AF software</td>
			<td>Leica Microsystems, Heidelberg, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Las X software</td>
			<td>Leica Microsystems, Heidelberg, Germany</td>
			<td></td>
			<td>https://www.leica-microsystems.com/products/microscope-software/p/leica-las-x-ls/</td>
		</tr>
		<tr>
			<td>Magnetic Holder with Suction Tubing</td>
			<td>BIOSCIENCE TOOLS, USA</td>
			<td>MTH-S</td>
			<td></td>
		</tr>
		<tr>
			<td>Microspin FV 2400</td>
			<td>Biosan, Latvia</td>
			<td>BS-010201-AAA</td>
			<td></td>
		</tr>
		<tr>
			<td>Minutien Pins</td>
			<td>Fine science tools, Canada</td>
			<td>26002-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Multi-spin MSC 3000</td>
			<td>Biosan, Latvia</td>
			<td>BS-010205-AAN</td>
			<td></td>
		</tr>
		<tr>
			<td>Oregon Green 488 BAPTA-1 pentapotassium salt</td>
			<td>Molecular Probes, USA</td>
			<td>O6806</td>
			<td>500 &#956;g</td>
		</tr>
		<tr>
			<td>Pipette</td>
			<td>Biohit, Russia</td>
			<td>720210</td>
			<td>0.5-10 &#181;L</td>
		</tr>
		<tr>
			<td>Pipette tip</td>
			<td>Biohit, Russia</td>
			<td>781349</td>
			<td>10 &#181;L</td>
		</tr>
		<tr>
			<td>Plasticine</td>
			<td>local producer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Single-use hypodermic needles</td>
			<td>Bbraun</td>
			<td>100 Sterican</td>
			<td>0.4&#215;40 mm</td>
		</tr>
		<tr>
			<td>Spreadsheet program</td>
			<td>Microsoft, USA</td>
			<td>Microsoft Office Excel</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereomicroscope, Leica M80</td>
			<td>Leica Microsystems , Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Suction electrode</td>
			<td>Kazakov A. SIMPLE SUCTION ELECTRODE FOR ELECTRIC STIMULATION OF BIOLOGICAL OBJECTS / A. Kazakov, M. Alexandrov, N. V. Zhilyakov et al. // International research journal.&#160;- 2015. - No. 9 (40) Part 3. - P. 13-16.</td>
			<td></td>
			<td>http://research-journal.org/biology/prostoj-vsasyvayushhij-elektrod-dlya-elektricheskoj-stimulyacii-biologicheskix-obektov/</td>
		</tr>
		<tr>
			<td>Sylgard 184 elastomer</td>
			<td>Dow Corning, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe</td>
			<td>local producer</td>
			<td></td>
			<td>0.5 mL</td>
		</tr>
		<tr>
			<td>Syringe</td>
			<td>local producer</td>
			<td></td>
			<td>60 mL</td>
		</tr>
	</tbody>
</table>

registration of calcium transients in mouse neuromuscular junction with high temporal resolution using confocal microscopy

Estimation of the presynaptic calcium level is a key task in studying synaptic transmission since calcium entry into the presynaptic cell triggers a cascade of events leading to neurotransmitter release. Moreover, changes in presynaptic calcium levels mediate the activity of many intracellular proteins and play an important role in synaptic plasticity. Studying calcium signaling is also important for finding ways to treat neurodegenerative diseases. The neuromuscular junction is a suitable model for studying synaptic plasticity, as it has only one type of neurotransmitter. This article describes the method for loading a calcium-sensitive dye through the cut nerve bundle into the mice's motor nerve endings. This method allows the estimation of all parameters related to intracellular calcium changes, such as basal calcium level and calcium transient. Since the influx of calcium from the cell exterior into the nerve terminals and its binding/unbinding to the calcium-sensitive dye occur within the range of a few milliseconds, a speedy imaging system is required to record these events. Indeed, high-speed cameras are commonly used for the registration of fast calcium changes, but they have low image resolution parameters. The protocol presented here for recording calcium transient allows extremely good spatial-temporal resolution provided by confocal microscopy.

After loading the preparation with dye according to the presented technique, most of the synapses located close to the nerve stump had a sufficient level of fluorescence (see Figure 2). After loading preparation with the dye andapplying the described method of registration and image processing, calcium transients with the desired spatial and temporal resolution were obtained (see Figure 4). The calcium transient has been recovered by the proposed method (see <st...

Watch this Scientific Journal Video about Registration of Calcium Transients in Mouse Neuromuscular Junction with High Temporal Resolution using Confocal Microscopy at JoVE.com

Registration of Calcium Transients in Mouse Neuromuscular Junction with High Temporal Resolution using Confocal Microscopy

The protocol describes the method of loading a fluorescent calcium dye through the cut nerve into mouse motor nerve terminals. In addition, a unique method for recording fast calcium transients in the peripheral nerve endings using confocal microscopy is presented.

Estimation of the presynaptic calcium level is a key task in studying synaptic transmission since calcium entry into the presynaptic cell triggers a ...

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