Name: successful in vivo calcium imaging with a head-mount miniaturized microscope in the amygdala of freely behaving mouse
Uploaded: 2020-08-26T14:00:00
Description: Watch this Scientific Journal Video about Successful In vivo Calcium Imaging with a Head-Mount Miniaturized Microscope in the Amygdala of Freely Behaving Mouse at JoVE.com

This work was supported by grants from Samsung Science and Technology Foundation (Project Number SSTF-BA1801-10).

All procedures were approved by the Animal Ethics Committee at the Korea Advanced Institute of Science and Technology. All experiments were performed in accordance with the guideline of the Institutional Animal Care and Use Committee.
NOTE: This protocol consists of six major steps: virus injection surgery, GRIN lens implant surgery, validation of GRIN lens implantation, baseplate attachment, optical recording of GCaMP signal during a behavior test, and data processing (Fi...

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Skillful surgery techniques are essential for achieving successful in vivo optical calcium imaging with head-mount miniature microscopy in deeper brain regions such as the amygdala as we described here. Therefore, although this protocol provides a guideline for optimized surgical processes of baseplate attachment and GRIN lens implantation, additional optimization processes might be necessary for critical steps. As mentioned in the protocol section, amygdala coordinates in surgery, airflow speed in baseplate attachment s...

Calcium is a ubiquitous second messenger, playing a crucial role in almost every cellular functions8. In neurons, action potential firing and synaptic input cause rapid change of intracellular free [Ca2+]9,10. Therefore, tracking calcium transients provides an opportunity to monitor neuronal activity. GECIs are powerful tools that allow for monitoring [Ca2+] in defined cell populations and intra-cellular compartments11,12. Among many different types of protein based calcium indicator, GCaMP, a Ca2+ probe based on a single GFP molecule13, is the most optimized and thus widely used GECI. Through multiple rounds of engineering, a number of variants of GCaMP has been developed12,14,15,16. We use one of the recently developed GCaMPs, GCaMP7b, in this protocol16. GCaMP sensors have greatly contributed to the study of neural circuit functions in a number of model organisms such as imaging of Ca2+ transients during development17, in vivo imaging in a specific cortical layer18, measurement of circuit dynamics in motor task learning19 and imaging of cell ensemble activity related with associative fear memory in the hippocampus and amygdala20,21.
Optical imaging of GECIs has several advantages22. Genetic encoding enables GECIs to be stably expressed for a long-term period of time in a specific subset of cells that are defined by genetic profile or specific patterns of anatomical connectivity. Optical imaging enables in vivo chronic simultaneous monitoring of hundreds to thousands of neurons in live animals. A few optical imaging systems have been developed for in vivo imaging and analysis of GECIs within the brain of freely behaving mice with head-mount miniaturized fluorescence microscopes21,23,24,25. Despite the in vivo optical imaging technique based on GECIs, GRIN lens, and a head-mount miniature microscope being a powerful tool to study the link between neural circuit activity and behavior, applying this technology to the amygdala has been difficult due to several technical issues related with targeting the GRIN lens to cells expressing GECIs in the amygdala without causing motion artifacts that severely reduce the quality of image acquisition and finding cells expressing GECIs. This protocol aims to provide a helpful guideline for surgical procedures of baseplate attachment and GRIN lens implantation that are critical steps for successful in vivo optical calcium imaging in the amygdala. Although this protocol targets the amygdala, most procedures described here are commonly applicable to other deeper brain regions. Although this protocol is based on a particular system (e.g., Inscopix), the same purpose may be easily achieved with other alternative systems.

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	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">26G needle</td>
			<td style="width:121px;">BD</td>
			<td align="right" style="width:161px;">302002</td>
			<td style="width:167px;">Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">AAV1-Syn-GCaMP7b-WPRE</td>
			<td style="width:121px;">Addgene</td>
			<td style="width:161px;">104493-AAV1</td>
			<td>Surgery</td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:216px;">AAV2/1-CaMKii&#945;-GFP</td>
			<td style="width:121px;">custom made</td>
			<td style="width:161px;"></td>
			<td>Surgery</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Acrylic-Dental cement (Ortho-jet Acrylic Pink)</td>
			<td style="width:121px;">Lang</td>
			<td style="width:161px;">1334-pink</td>
			<td>Surgery &#38; Baseplate Attachment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Air flow manipulator</td>
			<td style="width:121px;">Neurotar</td>
			<td style="width:161px;">NTR000253-04</td>
			<td>Baseplate Attachment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Amoxicillin</td>
			<td style="width:121px;">SIGMA</td>
			<td style="width:161px;">A8523-5G</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Baseplate</td>
			<td style="width:121px;">INSCOPIX</td>
			<td style="width:161px;">1050-002192</td>
			<td>Baseplate Attachment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Baseplate cover</td>
			<td style="width:121px;">INSCOPIX</td>
			<td style="width:161px;">1050-002193</td>
			<td>Baseplate Attachment</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Behavioral apparatus (chamber)</td>
			<td style="width:121px;">Coulbourn Instrument</td>
			<td style="width:161px;">Testcage</td>
			<td>Behavior test</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Behavioral apparatus (software)</td>
			<td style="width:121px;">Coulbourn Instrument</td>
			<td style="width:161px;">Freeze Frame</td>
			<td>Behavior test</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Carbon cage</td>
			<td style="width:121px;">Neurotar</td>
			<td style="width:161px;">180mm x 70mm</td>
			<td>Baseplate Attachment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Carprofen</td>
			<td style="width:121px;">SIGMA</td>
			<td style="width:161px;">PHR1452-1G</td>
			<td>Surgery</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Data processing software</td>
			<td style="width:121px;">INSCOPIX</td>
			<td style="width:161px;">INSCOPIX Data Processing Software</td>
			<td>Baseplate Attachment &#38; Behavior test</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Dexamethasone</td>
			<td style="width:121px;">SIGMA</td>
			<td style="width:161px;">D1756-500MG</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Drill</td>
			<td style="width:121px;">Seyang</td>
			<td style="width:161px;">marathon-4</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Drill bur</td>
			<td style="width:121px;">ELA</td>
			<td style="width:161px;">US1/2, Shank104</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Glass needle</td>
			<td style="width:121px;">WPI</td>
			<td style="width:161px;">PG10165-4</td>
			<td>Surgery</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">GRIN lens (INSCOPIX Proview Lens Probe)</td>
			<td style="width:121px;">INSCOPIX</td>
			<td style="width:161px;">1050-002208</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Hamilton Syringe</td>
			<td style="width:121px;">Hamilton</td>
			<td align="right" style="width:161px;">84875</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Head plate</td>
			<td style="width:121px;">Neurotar</td>
			<td style="width:161px;">Model 5</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Hex-key</td>
			<td style="width:121px;">INSCOPIX</td>
			<td style="width:161px;">1050-004195</td>
			<td>Baseplate Attachment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Laptop computer</td>
			<td style="width:121px;">Samsung</td>
			<td style="width:161px;">NT950XBV</td>
			<td>Surgery &#38; Baseplate Attachment</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Lens holder, Stereotaxic rod (INSCOPIX proview implant kit)</td>
			<td style="width:121px;">INSCOPIX</td>
			<td style="width:161px;">1050-004223</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Microscope gripper</td>
			<td style="width:121px;">INSCOPIX</td>
			<td style="width:161px;">1050-002199</td>
			<td>Baseplate Attachment</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Microscope, DAQ software, hardware</td>
			<td style="width:121px;">INSCOPIX</td>
			<td style="width:161px;">nVista 3.0</td>
			<td>Baseplate Attachment &#38; Behavior test</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Mobile homecage</td>
			<td style="width:121px;">Neurotar</td>
			<td style="width:161px;">MHC V5</td>
			<td>Baseplate Attachment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Moterized arm</td>
			<td style="width:121px;">Neurostar</td>
			<td style="width:161px;">Customized</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Moterized arm software</td>
			<td style="width:121px;">Neurostar</td>
			<td style="width:161px;">Customized</td>
			<td>Surgery</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">NI board</td>
			<td style="width:121px;">National instrument</td>
			<td style="width:161px;"></td>
			<td>Behavior test</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Removable epoxy bond</td>
			<td style="width:121px;">WPI</td>
			<td style="width:161px;">Kwik-Cast</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Resin cement (Super-bond)</td>
			<td style="width:121px;">Sun medical</td>
			<td style="width:161px;">Super bond C&#38;B</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Skull screw</td>
			<td style="width:121px;">Stoelting</td>
			<td align="right" style="width:161px;">51457</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Stereotaxic electrode holder</td>
			<td style="width:121px;">ASI</td>
			<td style="width:161px;">EH-600</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Stereotaxic frame</td>
			<td style="width:121px;">Stoelting</td>
			<td align="right" style="width:161px;">51600</td>
			<td>Surgery</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Stereotaxic manipulator</td>
			<td style="width:121px;">Stoelting</td>
			<td align="right" style="width:161px;">51600</td>
			<td>Baseplate Attachment</td>
		</tr>
	</tbody>
</table>

successful in vivo calcium imaging with a head-mount miniaturized microscope in the amygdala of freely behaving mouse

In vivo real-time monitoring of neuronal activities in freely moving animals is one of key approaches to link neuronal activity to behavior. For this purpose, an in vivo imaging technique that detects calcium transients in neurons using genetically encoded calcium indicators (GECIs), a miniaturized fluorescence microscope, and a gradient refractive index (GRIN) lens has been developed and successfully applied to many brain structures1,2,3,4,5,6. This imaging technique is particularly powerful because it enables chronic simultaneous imaging of genetically defined cell populations for a long-term period up to several weeks. Although useful, this imaging technique has not been easily applied to brain structures that locate deep within the brain such as amygdala, an essential brain structure for emotional processing and associative fear memory7. There are several factors that make it difficult to apply the imaging technique to the amygdala. For instance, motion artifacts usually occur more frequently during the imaging conducted in the deeper brain regions because a head-mount microscope implanted deep in the brain is relatively unstable. Another problem is that the lateral ventricle is positioned close to the implanted GRIN lens and its movement during respiration may cause highly irregular motion artifacts that cannot be easily corrected, which makes it difficult to form a stable imaging view. Furthermore, because cells in the amygdala are usually quiet at a resting or anesthetized state, it is hard to find and focus the target cells expressing GECI in the amygdala during baseplating procedure for later imaging. This protocol provides a helpful guideline for how to efficiently target cells expressing GECI in the amygdala with head-mount miniaturized microscope for successful in vivo calcium imaging in such a deeper brain region. It is noted that this protocol is based on a particular system (e.g., Inscopix) but not restricted to it.

Validation of GRIN lens implantation 
Before chronically attaching the baseplate to the brain by cementing, the GRIN lens implantation needs to be validated. In animals with successful lens implantation, both GCaMP expressing cells and blood vessels were clearly observed within a focal plane range determined by the distance between objective lens of microscope and implanted GRIN lens (Figure 2A and B). In contrast, in animals with off-t...

Watch this Scientific Journal Video about Successful In vivo Calcium Imaging with a Head-Mount Miniaturized Microscope in the Amygdala of Freely Behaving Mouse at JoVE.com

Successful In vivo Calcium Imaging with a Head-Mount Miniaturized Microscope in the Amygdala of Freely Behaving Mouse

In vivo microendoscopic calcium imaging is an invaluable tool that enables real-time monitoring of neuronal activities in freely behaving animals. However, applying this technique to the amygdala has been difficult. This protocol aims to provide a useful guideline for successfully targeting amygdala cells with a miniaturized microscope in mice.

In vivo real-time monitoring of neuronal activities in freely moving animals is one of key approaches to link neuronal activity to behavior. For this ...

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