Name: head implants for the neuroimaging of awake, head-fixed rats
Uploaded: 2022-09-07T13:40:00
Description: Watch this Scientific Journal Video about Head Implants for the Neuroimaging of Awake, Head-Fixed Rats at JoVE.com

We acknowledge Clara Jones, James Stirwalt, Linh Hoang, Young Joon Ha, and Amirsoheil Zareh for their help during training of the rats and preparation of the slings. Funding was provided by the National Institutes of Health (NIH, Grant Number: NS119852) and Leducq Foundation (Grant Number:15CVD02).

All procedures were compliant with National Institute of Health guidelines and approved by the University of California, Irvine Animal Care and Use Committee. Seven males and one female rat (Sprague-Dawley, weight: 185-350 g) were used in this study. After study completion, the rats were sacrificed using carbon dioxide overdose.
1. Design of different components
<ol>
	<li>Design of the head implant:
	<ol>
		<li>Make the head implant using CAD software (F...

<ol>
	<li>Cicero, L., Fazzotta, S., Palumbo, V. D., Cassata, G., Lo Monte, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anesthesia+protocols+in+laboratory+animals+used+for+scientific+purposes.">Anesthesia protocols in laboratory animals used for scientific purposes.</a> Acta Biomedica. 89 (3), 337-342 (2018).</li><li>Lythgoe, M. F., Sibson, N. R., Harris, N. 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C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+method+for+functional+brain+imaging+in+awake+minimally+restrained+rats.">Novel method for functional brain imaging in awake minimally restrained rats.</a> Journal of Neurophysiology. 116 (1), 61-80 (2016).</li><li>Stenroos, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Awake+rat+brain+functional+magnetic+resonance+imaging+using+standard+radio+frequency+coils+and+a+3D+printed+restraint+kit.">Awake rat brain functional magnetic resonance imaging using standard radio frequency coils and a 3D printed restraint kit.</a> Frontiers in Neuroscience. 12, 548 (2018).</li><li>Vogler, G. A., Suckow, M. A., Weisbroth, S. H., Franklin, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+19+-+Anesthesia+and+Analgesia+(Second+Edition).">Chapter 19 - Anesthesia and Analgesia (Second Edition).</a> The Laboratory Rat. , 627-664 (2006).</li><li>Schwarz, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+head-fixed+behaving+rat--Procedures+and+pitfalls.">The head-fixed behaving rat--Procedures and pitfalls.</a> Somatosensory and Mot Research. 27 (4), 131-148 (2010).</li><li>Roh, M., Lee, K., Jang, I. S., Suk, K., Lee, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acrylic+resin+molding+based+head+fixation+technique+in+rodents.">Acrylic resin molding based head fixation technique in rodents.</a> Journal of Visualized Experiments. (107), e53064 (2016).</li><li>Ferris, C. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applications+in+awake+animal+magnetic+resonance+imaging.">Applications in awake animal magnetic resonance imaging.</a> Frontiers in Neuroscience. 16, 854377 (2022).</li><li>Tiran, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcranial+functional+ultrasound+imaging+in+freely+moving+awake+mice+and+anesthetized+young+rats+without+contrast+agent.">Transcranial functional ultrasound imaging in freely moving awake mice and anesthetized young rats without contrast agent.</a> Ultrasound in Medicine and Biology. 43 (8), 1679-1689 (2017).</li><li>Desjardins, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Awake+mouse+imaging:+From+two-photon+microscopy+to+blood+oxygen+level-dependent+functional+magnetic+resonance+imaging.">Awake mouse imaging: From two-photon microscopy to blood oxygen level-dependent functional magnetic resonance imaging.</a> Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. 4 (6), 533-542 (2019).</li><li>Koletar, M. M., Dorr, A., Brown, M. E., McLaurin, J., Stefanovic, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Refinement+of+a+chronic+cranial+window+implant+in+the+rat+for+longitudinal+in+vivo+two-photon+fluorescence+microscopy+of+neurovascular+function.">Refinement of a chronic cranial window implant in the rat for longitudinal in vivo two-photon fluorescence microscopy of neurovascular function.</a> Scientific Reports. 9, 5499 (2019).</li><li>Drew, P. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+optical+access+through+a+polished+and+reinforced+thinned+skull.">Chronic optical access through a polished and reinforced thinned skull.</a> Nature Methods. 7 (12), 981-984 (2010).</li><li>Cao, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+and+oxygen-metabolic+photoacoustic+microscopy+of+the+awake+mouse+brain.">Functional and oxygen-metabolic photoacoustic microscopy of the awake mouse brain.</a> Neuroimage. 150, 77-87 (2017).</li><li>Grinvald, A., Frostig, R. D., Siegel, R. 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The use of awake, head-fixed rat imaging offers many advantages in terms of ease and customization. The custom-designed slings allow the rats to be wrapped through breathable netting material, eliminating the need to enclose animals in closed, plastic restraining chambers for extended periods of time10,11. Rats are kept calm and stress-free throughout the long durations of successive imaging sessions using a very low dose of acepromazine below the levels of mild ...

Most of the basic, preclinical, and translational scientific neuroimaging investigations are acquired from anesthetized animals1,2. Anesthetics ease experimentation but continuously influence the brain&#39;s and body&#39;s metabolism, blood pressure, and heart rate3. The type of anesthetic and the duration and route of administration add confounding variables to data interpretation that could contribute to reproducibility and translational failures4. A major bottleneck of awake, head-fixed rat neuroimaging studies is the requirement to keep the rat stationary and calm throughout the preparation and data acquisition processes. Small movements produce unwarranted motion artifacts, which can adversely affect data analysis and interpretations.
A new model of neuroimaging from awake, head-fixed rats using customized slings, three-dimensional (3D)-printed head implants, head caps, and a headframe has been devised that offers several advantages for easy experimentation. The 3D head implant is light and covers a small portion of the skull needed for transfixing. The 3D-printed head implants and caps are designed using computer-aided design (CAD) software. The protocols of whisker stimulation, data acquisition, data analysis, and results from anesthetized rats have been described in detail in previous work5,6,7.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr >
			<td >Rats</td>
			<td >Charles River</td>
			<td >Sprague Dawley</td>
			<td ></td>
		</tr>
		<tr >
			<td >Isoflurane</td>
			<td >Pivetal</td>
			<td >21295098</td>
			<td>General anesthetic</td>
		</tr>
		<tr >
			<td >Lidocaine HCl 2% injection</td>
			<td >Phoenix</td>
			<td >L-2000-04</td>
			<td>Local anesthetic</td>
		</tr>
		<tr >
			<td >Atropine sulfate injection</td>
			<td >Vedco</td>
			<td >5098907512</td>
			<td>Help in respiration</td>
		</tr>
		<tr >
			<td >Lactated Ringer&#39;s injection solution</td>
			<td >Vedco</td>
			<td >50989088317</td>
			<td></td>
		</tr>
		<tr >
			<td >Flunixin injection</td>
			<td >Vedco</td>
			<td >6064408670</td>
			<td>Pain management</td>
		</tr>
		<tr >
			<td >Enrosite injection (Enrofloxacin 2.27%)</td>
			<td >VetOne</td>
			<td >501084</td>
			<td>Avoid infection</td>
		</tr>
		<tr >
			<td >PromAce injection (Acepromazine maleate)</td>
			<td >Beohringer Ingelheim</td>
			<td >136059</td>
			<td></td>
		</tr>
		<tr >
			<td >Animax ointment</td>
			<td >Dechra Veterinary Products</td>
			<td >122-75</td>
			<td>active ingredients of nystatin 1000units per gram, neomycin sulfate 2.5mg per gram, thiostrepton 2500 units per gram, and triamcinolone acetonide 1mg per gram</td>
		</tr>
		<tr >
			<td >Puralube ophthalmic ointment</td>
			<td >Dechra Veterinary Products</td>
			<td >211-38</td>
			<td></td>
		</tr>
		<tr >
			<td >Povidone-iodine PVP prep pads</td>
			<td >Medline</td>
			<td >MDS093917</td>
			<td>Betadine generic</td>
		</tr>
		<tr >
			<td >Isopropyl alcohol swabs</td>
			<td >BD</td>
			<td >326895</td>
			<td></td>
		</tr>
		<tr >
			<td >Vetbond tissue adhesive</td>
			<td >3M</td>
			<td >1469SB</td>
			<td></td>
		</tr>
		<tr >
			<td >Bur (drill bit), standard operatory carbide</td>
			<td >SS White Burs</td>
			<td >14829</td>
			<td>#3 bur</td>
		</tr>
		<tr >
			<td >Screws, 00-90 x 1/8 flat head stainless steel</td>
			<td >J.I. Morris</td>
			<td >F0090CE125</td>
			<td>Anchor screws</td>
		</tr>
		<tr >
			<td >Stereotaxic system</td>
			<td >Kopf Instruments</td>
			<td >1430</td>
			<td></td>
		</tr>
		<tr >
			<td >Homeothermic heating blanket</td>
			<td >Harvard Apparatus</td>
			<td >50-7220-F</td>
			<td></td>
		</tr>
		<tr >
			<td >Pulse oximeter &#38; heart rate monitor</td>
			<td >Kent Scientific</td>
			<td >MouseStat Jr.</td>
			<td></td>
		</tr>
		<tr >
			<td >Petrolatum</td>
			<td >Fisher Scientific</td>
			<td >P66-1LB</td>
			<td>Vaseline generic</td>
		</tr>
		<tr >
			<td >Wire, bare copper</td>
			<td >Fisher Scientific</td>
			<td >15-545-2C</td>
			<td>20 gauge</td>
		</tr>
		<tr >
			<td >Teets Cold Cure powder</td>
			<td >Pearson Dental</td>
			<td >C73-0054&#160;</td>
			<td>active ingredient: Methyl Methacrylate</td>
		</tr>
		<tr >
			<td >Teets Cold Cure liquid</td>
			<td >Pearson Dental</td>
			<td >C73-0078&#160;</td>
			<td>active ingredient: Methyl Methacrylate</td>
		</tr>
		<tr >
			<td >Silicone mold rubber</td>
			<td >Smooth-On</td>
			<td >Body Double Fast</td>
			<td>silicon polymer</td>
		</tr>
		<tr >
			<td >Metricide 28 (Germicide)</td>
			<td >Metrex</td>
			<td >Oct-05</td>
			<td></td>
		</tr>
		<tr >
			<td >India ink, black</td>
			<td >Pelikan</td>
			<td >301051</td>
			<td></td>
		</tr>
		<tr >
			<td >Dental drill</td>
			<td >NSK Dental</td>
			<td >Ultimate XL-F</td>
			<td></td>
		</tr>
		<tr >
			<td >3D printer</td>
			<td >Prusa Research</td>
			<td >i3 MK3S+</td>
			<td></td>
		</tr>
		<tr >
			<td >Sew on fasteners</td>
			<td >Velcro</td>
			<td >90030</td>
			<td></td>
		</tr>
		<tr >
			<td >Pet screening utility fabric</td>
			<td >Joann</td>
			<td >10173334</td>
			<td>Netting material</td>
		</tr>
		<tr >
			<td >Bur (drill bit), standard operatory carbide</td>
			<td >SS White Burs</td>
			<td >14829</td>
			<td>#1 bur</td>
		</tr>
	</tbody>
</table>

head implants for the neuroimaging of awake, head-fixed rats

Anesthetics, commonly used in preclinical and fundamental scientific research, have a depressive influence on the metabolic, neuronal, and vascular functions of the brain and can adversely influence neurophysiological results. The use of awake animals for research studies is advantageous but poses the major challenge of keeping the animals calm and stationary to minimize motion artifacts throughout data acquisition. Awake imaging in smaller-sized rodents (e.g., mice) is very common but remains scant in rats as rats are bigger, stronger, and have a greater tendency to oppose movement restraints and head fixation over the long durations required for imaging. A new model of neuroimaging of awake, head-fixed rats using customized hand-sewn slings, 3D-printed head implants, head caps, and a headframe is described. The results acquired following a single trial of single-whisker stimulation suggest an increase in the intensity of the evoked functional response. The acquisition of the evoked functional response from awake, head-fixed rats is faster than that from anesthetized rats, reliable, reproducible, and can be used for repeated longitudinal studies.

The representative optical imaging signals from a single trial of an anesthetized rat and the summed response (of 40 collected trials) of an awake rat are shown (Figure 4). The signal intensity for single-whisker stimulation of an awake rat can be visualized at a higher threshold than for the anesthetized rat, showing a stronger signal from the awake animal. The C2 whiskers of rats are stimulated at 5 Hz for 1 s, and the functional response is displayed as a fractional change compared to the...

Watch this Scientific Journal Video about Head Implants for the Neuroimaging of Awake, Head-Fixed Rats at JoVE.com

Head Implants for the Neuroimaging of Awake, Head-Fixed Rats

A detailed new procedure for functional imaging of awake, head-fixed rats is described.

Anesthetics, commonly used in preclinical and fundamental scientific research, have a depressive influence on the metabolic, neuronal, and vascular ...

Most basic and translational work comes from anesthetized animals. Anesthetics can add confounding variables to data analysis and interpretation. This work enables awake imaging in rats to circumvent that issue.This design is quite simple. The whole assembly is lightweight, so it does not impair the normal life of the animal. This means it can also be used for long-term chronic imaging.Helping to demonstrate this procedure will be Dr.Mehwish Bhatti, a senior postdoc from our laboratory. Begin by making the head implant using CAD software to image the area posterior to the bregma and adjacent to the midline centered on the somatosensory cortex. Ensure that the head implant covers an area of 0.9 to 1.9 millimeters on the skull away from the imaging area.Use only three screws to anchor the head implant on the rat skull. Design all the screw holes on the opposite side of the midline in the contralateral part of the image hemisphere. To allow wires to fix the head cap to the head implant, place a hollow bar in the upper part of the head implant.Next, design the cap, ensuring that it covers the imaging area entirely and protects it from any trauma. Add a curvature to the head cap so that it aligns to the shape of the head without causing difficulty to the animal's daily activities in the standard enriched cages. Cut the inner side of the head cap in a wider rectangular shape so that the upper part of the head implant can fit into it.Perpendicular to this rectangle, cut two other rectangular regions to anchor the head cap to the head implant. To fix the head cap on the rat's head, pass the wires through the upper hollowed bar of the head implant. Design the head frame so that one cut part can move through the upper bar of the head implant and is fixed using a clamp.To make the contralateral side accessible for imaging, angle the other cut part to provide extra strength for keeping the rat head fixed. Print the head implant and head cap using the 3D printer. Measure the weight of the animal to calculate the amount of anesthetic to be administered.Anesthetize the animal by injecting sodium pentobarbital intraperitoneally. Several anesthesia alternatives can be used in this surgery such as isoflurane, ketamine, or xylazine. Inject atropine intramuscularly to reduce mucus secretions while breathing.Using a hair trimmer, shave the head of the rat starting between the eyes to the back of the ears five millimeters centered around the midline. Then monitor the partial oxygen saturation and heart rate using a pulse oximeter and heart rate monitor probe secured to the rat's hind leg. Wipe the rat's head and the surrounding area thrice with Betadine and 70%alcohol wipes alternatively.Fix the rat in a stereotaxic system. Next, insert a petroleum jelly lubricated rectal probe to measure the rat's body temperature and maintain it through the heating blanket's feedback system to avoid hypothermia after anesthetic administration. Apply ophthalmic ointment to both eyes to prevent drying.Administer 2%local anesthetic subcutaneously over the surgical site and three millimeters of lactated Ringer's solution at room temperature subcutaneously to prevent dehydration and provide nourishment during surgery. Using sharp surgical scissors, remove the part of the skin over the surgical site. Dissect and remove part of the skin between the ear and eye on the temporal part of the head.Using a scalpel, remove the underlying skin tissue to expose the skull. Then clean the skull using sterilized cotton gauze. Cut the temporal muscle and expose the skull area on the contralateral hemisphere for the head implant.Place the head implant on the skull to ascertain the location of anchoring screws for the implant. Now mark the skull using India ink for drilling the screws with the drill bit one. Drill the burr holes for the screws using dental drill bit three and screw the head implant in place.Dry the skull using sterile gauze and apply a thin layer of tissue adhesive around and beneath the head implant to glue it to the skull. Use dental cement to support the head implant in place further and let the cement dry for two to three minutes. Further, use dental drill bit three to decrease the thickness of a 7.5 millimeter by 7.5 millimeter area on the left side of the skull just posterior the bregma and lateral to the midline to 50 micrometers.Apply topical antibiotic ointment over the surgical site and then cover it with a thin layer of silicone rubber to protect the thin skull. Next, cover the surgical site using the head cap and fix it in place with the two small pieces of wires going through both the head implant and the head cap. Apply silicone rubber to cover the head cap and skull to stabilize the head cap further on the rat's head.Administer buprenorphine and antibiotics intraperitoneally to manage pain and inflammation and prevent in infection respectively. The optical imaging signals from the summed response of an awake rat and a single trial of an anesthetized rat are shown. The functional response of the awake head fixed rat is 140 times stronger than that of the anesthetized rat.Be careful not to add too much cement over the head plate. It can obstruct the cap from being properly fixed. This method can be widely applied to awake head fixed thin skull neuroimaging.With craniotomies, it can be extended to other neuroimaging protocols including functional ultrasound imaging, calcium imaging, and fluorescence imaging. Awake imaging will allow for a new body of work without the confounding variables introduced with anesthetics.

head-implants-for-the-neuroimaging-of-awake-head-fixed-rats

Research

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Neuroscience

In Vitro Modeling of Cancerous Neural Invasion: The Dorsal Root Ganglion Model

One way that solid tumors disseminate is through neural invasion. This route is well-known in cancers of the head and neck, prostate, and pancreas. These neurotropic cancer cells have a unique ability to migrate unidirectionally along nerves towards the central nervous system (CNS). The dorsal root ganglia (DRG)/cancer cell model is a three dimensional (3D) in vitro model frequently used for studying the interaction between neural stroma and cancer cells. In this model, mouse or human cancer cell lines are grown in ECM adjacent to preparations of freshly dissociated cultured DRG. In this article, the DRG isolation protocol from mice, and implantation in petri dishes for co-culturing with pancreatic cancer cells are demonstrated. Five days after implantation, the cancer cells made contact with the DRG neurites. Later, these cells formed bridgeheads to facilitate more extensive polarized, neurotropic migration of cancer cells.

In Vitro Modeling of Cancerous Neural Invasion: The Dorsal Root Ganglion Model

This video article shows the use of the dorsal root ganglia (DRG)/cancer cell model in pancreatic ductal adenocarcinoma.

One way that solid tumors disseminate is through neural invasion. This route is well-known in cancers of the head and neck, prostate, and pancreas. These ...

Neuroimaging Field Methods Using Functional Near Infrared Spectroscopy (NIRS) Neuroimaging to Study Global Child Development: Rural Sub-Saharan Africa

Portable neuroimaging approaches provide new advances to the study of brain function and brain development with previously inaccessible populations and in remote locations. This paper shows the development of field functional Near Infrared Spectroscopy (fNIRS) imaging to the study of child language, reading, and cognitive development in a rural village setting of C&#244;te d&#39;Ivoire. Innovation in methods and the development of culturally appropriate neuroimaging protocols allow&#160;a first-time look into the brain&#39;s development and children&#39;s learning outcomes in understudied environments. This paper demonstrates protocols for transporting and setting up a mobile laboratory, discusses considerations for field versus laboratory neuroimaging, and presents a guide for developing neuroimaging consent procedures and building meaningful long-term collaborations with local government and science partners. Portable neuroimaging methods can be used to study complex child development contexts, including the impact of significant poverty and adversity on brain development. The protocol presented here has been developed for use in C&#244;te d&#39;Ivoire, the world&#39;s primary source of cocoa, and where reports of child labor in the cocoa sector are common. Yet, little is known about the impact of child labor on brain development and learning. Field neuroimaging methods have the potential to yield new insights into such urgent issues, and the development of children globally.

Neuroimaging Field Methods Using Functional Near Infrared Spectroscopy NIRS Neuroimaging to Study Global Child Development: Rural Sub-Saharan Africa

Portable neuroimaging approaches (functional Near Infrared Spectroscopy) provide advances to the study of the brain in previously inaccessible regions; here, rural C&#244;te d&#39;Ivoire. Innovation in methods and development of culturally-appropriate neuroimaging protocols permits novel study of the brain&#39;s development and children&#39;s learning outcomes in environments with significant poverty and adversity.

Portable neuroimaging approaches provide new advances to the study of brain function and brain development with previously inaccessible populations and in ...

Visualizing Protein Kinase A Activity In Head-fixed Behaving Mice Using In Vivo Two-photon Fluorescence Lifetime Imaging Microscopy

Neuromodulation exerts powerful control over brain function. Dysfunction of neuromodulatory systems results in neurological and psychiatric disorders. Despite their importance, technologies for tracking neuromodulatory events with cellular resolution are just beginning to emerge. Neuromodulators, such as dopamine, norepinephrine, acetylcholine, and serotonin, trigger intracellular signaling events via their respective G protein-coupled receptors to modulate neuronal excitability, synaptic communications, and other neuronal functions, thereby regulating information processing in the neuronal network. The above mentioned neuromodulators converge onto the cAMP/protein kinase A (PKA) pathway. Therefore, in vivo PKA imaging with single-cell resolution was developed as a readout for neuromodulatory events in a manner analogous to calcium imaging for neuronal electrical activities. Herein, a method is presented to visualize PKA activity at the level of individual neurons in the cortex of head-fixed behaving mice. To do so, an improved A-kinase activity reporter (AKAR), called tAKAR&#945;, is used, which is based on F&#246;rster resonance energy transfer (FRET). This genetically-encoded PKA sensor is introduced into the motor cortex via in utero electroporation (IUE) of DNA plasmids, or stereotaxic injection of adeno-associated virus (AAV). FRET changes are imaged using two-photon fluorescence lifetime imaging microscopy (2pFLIM), which offers advantages over ratiometric FRET measurements for quantifying FRET signal in light-scattering brain tissue. To study PKA activities during enforced locomotion, tAKAR&#945; is imaged through a chronic cranial window above the cortex of awake, head-fixed mice, which run or rest on a speed-controlled motorized treadmill. This imaging approach will be applicable to many other brain regions to study corresponding behavior-induced PKA activities and to other FLIM-based sensors for in vivo imaging.

A procedure is presented to visualize protein kinase A activities in head-fixed, behaving mice. An improved A-kinase activity reporter, tAKAR&#945;, is expressed in cortical neurons and made accessible for imaging through a cranial window. Two-photon fluorescence lifetime imaging microscopy is used to visualize PKA activities in vivo during enforced locomotion.

Neuromodulation exerts powerful control over brain function. Dysfunction of neuromodulatory systems results in neurological and psychiatric disorders. ...

Injections of AAV Vectors for Optogenetics in Anesthetized and Awake Behaving Non-Human Primate Brain

Optogenetic techniques have revolutionized neuroscience research and are poised to do the same for neurological gene therapy. The clinical use of optogenetics, however, requires that safety and efficacy be demonstrated in animal models, ideally in non-human primates (NHPs), because of their neurological similarity to humans. The number of candidate vectors that are potentially useful for neuroscience and medicine is vast, and no high-throughput means to test these vectors yet exists. Thus, there is a need for techniques to make multiple spatially and volumetrically accurate injections of viral vectors into NHP brain that can be identified unambiguously through postmortem histology. Described herein is such a method. Injection cannulas are constructed from coupled polytetrafluoroethylene and stainless-steel tubes. These cannulas are autoclavable, disposable, and have low minimal-loading volumes, making them ideal for the injection of expensive, highly concentrated viral vector solutions. An inert, red-dyed mineral oil fills the dead space and forms a visible meniscus with the vector solution, allowing instantaneous and accurate measurement of injection rates and volumes. The oil is loaded into the rear of the cannula, reducing the risk of co-injection with the vector. Cannulas can be loaded in 10 min, and injections can be made in 20 min. This procedure is well suited for injections into awake or anesthetized animals. When used to deliver high-quality viral vectors, this procedure can produce robust expression of optogenetic proteins, allowing optical control of neural activity and behavior in NHPs.

As currently implemented, optogenetics in non-human primates requires injection of viral vectors into the brain. An optimal injection method should be reliable and, for many applications, capable of targeting individual sites of arbitrary depth that are readily and unambiguously identified in postmortem histology. An injection method with these properties is presented.

Optogenetic techniques have revolutionized neuroscience research and are poised to do the same for neurological gene therapy. The clinical use of ...

Assessing Changes in Synaptic Plasticity Using an Awake Closed-Head Injury Model of Mild Traumatic Brain Injury

Mild traumatic brain injuries (mTBIs) are a prevalent health issue in North America. There is increasing pressure to utilize ecologically valid models of closed-head mTBI in the preclinical setting to increase translatability to the clinical population. The awake closed-headed injury (ACHI) model uses a modified controlled cortical impactor to deliver closed-headed injury, inducing clinically relevant behavioral deficits without the need for a craniotomy or the use of an anesthetic.
This technique does not normally induce fatalities, skull fractures, or brain bleeds, and is more consistent with being a mild injury. Indeed, the mild nature of the ACHI procedure makes it ideal for studies investigating repetitive mTBI (r-mTBI). Growing evidence indicates that r-mTBI can result in a cumulative injury that produces behavioral symptoms, neuropathological changes, and neurodegeneration. r-mTBI is common in youths playing sports, and these injuries occur during a period of robust synaptic reorganization and myelination, making the younger population particularly vulnerable to the long-term influences of r-mTBI.
Further, r-mTBI occurs in cases of intimate partner violence, a condition for which there are few objective screening measures. In these experiments, synaptic function was assessed in the hippocampus in juvenile rats that had experienced r-mTBI using the ACHI model. Following the injuries, a tissue slicer was utilized to make hippocampal slices to evaluate bidirectional synaptic plasticity in the hippocampus at either 1 or 7 days following the r-mTBI. Overall, the ACHI model provides researchers with an ecologically valid model to study changes in synaptic plasticity following mTBI and r-mTBI.

Here, it is demonstrated how an awake closed-head injury model can be used for examining the effects of repeated mild traumatic brain injury (r-mTBI) on synaptic plasticity in the hippocampus. The model replicates important features of r-mTBI in patients and is used in conjunction with in vitro electrophysiology.

Mild traumatic brain injuries (mTBIs) are a prevalent health issue in North America. There is increasing pressure to utilize ecologically valid models of ...

Abdominal VNS for Treating Inflammatory Conditions in Rat Models

Implantation Surgery for Abdominal Vagus Nerve Stimulation and Recording Studies in Awake Rats

Abdominal vagus nerve stimulation (VNS) can be applied to the subdiaphragmatic branch of the vagus nerve of rats. Due to its anatomical location, it does not have any respiratory and cardiac off-target effects commonly associated with cervical VNS. The lack of respiratory and cardiac off-target effects means that the intensity of stimulation does not need to be lowered to reduce side effects commonly experienced during cervical VNS. Few recent studies demonstrate the anti-inflammatory effects of abdominal VNS in rat models of inflammatory bowel disease, rheumatoid arthritis, and glycemia reduction in a rat model of type 2 diabetes. Rat is a great model to explore the potential of this technology because of the well-established anatomy of the vagus nerve, the large size of the nerve that allows easy handling, and the availability of many disease models. Here, we describe the methods for cleaning and sterilizing the abdominal VNS electrode array and surgical protocol in rats. We also describe the technology required for confirmation of suprathreshold stimulation by recording evoked compound action potentials. Abdominal VNS has the potential to offer selective, effective treatment for a variety of conditions, including inflammatory diseases, and the application is expected to expand similarly to cervical VNS.

Author Spotlight: Exploring Abdominal VNS for Inflammatory Conditions

The present protocol describes the surgical technique for implanting an electrode array onto the abdominal vagus nerve in rats, along with methods for chronic electrophysiology testing and stimulation using the implanted device.

Abdominal vagus nerve stimulation (VNS) can be applied to the subdiaphragmatic branch of the vagus nerve of rats. Due to its anatomical location, it does ...

Multilayer Imaging with Microprism in Head-Fixed and Freely Moving Animals

Long-Term Imaging of Identified Neural Populations using Microprisms in Freely Moving and Head-Fixed Animals

With the advancement of multi-photon microscopy and molecular technologies, fluorescence imaging is rapidly growing to become a powerful approach for studying the structure, function, and plasticity of living brain tissues. In comparison to conventional electrophysiology, fluorescence microscopy can capture the neural activity as well as the morphology of the cells, enabling long-term recordings of the identified neuron populations at single-cell or subcellular resolution. However, high-resolution imaging typically requires a stable, head-fixed setup that restricts the movement of the animal, and the preparation of a flat surface of transparent glass allows visualization of neurons at one or more horizontal planes but is limited in studying the vertical processes running across different depths. Here, we describe a procedure to combine a head plate fixation and a microprism that gives multilayer and multimodal imaging. This surgical preparation not only gives access to the entire column of the mouse visual cortex but allows two-photon imaging in a head-fixed position and one-photon imaging in a freely moving paradigm. Using this approach, one can sample identified cell populations across different cortical layers, register their responses under head-fixed and freely moving states, and track the long-term changes over months. Thus, this method provides a comprehensive assay of the microcircuits, enabling direct comparison of neural activities evoked by well-controlled stimuli and under a natural behavioral paradigm.

Author Spotlight: Comparative Imaging of Neural Activity in Awake and Freely Moving States

When integrated with a head-plate and an optical design compatible with both single- and two-photon microscopes, the microprism lens presents a significant advantage in measuring neural responses in a vertical column under diverse conditions, including well-controlled experiments in head-fixed states or natural behavioral tasks in freely moving animals.

With the advancement of multi-photon microscopy and molecular technologies, fluorescence imaging is rapidly growing to become a powerful approach for ...

Fabrication and Surgical Implantation of Electromyographic Electrodes in Mice

Recording Forelimb Muscle Activity in Head&#45;Fixed Mice with Chronically Implanted EMG Electrodes

Powerful genetic and molecular tools available in mouse systems neuroscience research have enabled researchers to interrogate motor system function with unprecedented precision in head-fixed mice performing a variety of tasks. The small size of the mouse makes the measurement of motor output difficult, as the traditional method of electromyographic (EMG) recording of muscle activity was designed for larger animals like cats and primates. Pending commercially available EMG electrodes for mice, the current gold-standard method for recording muscle activity in mice is to make electrode sets in-house. This article describes a refinement of established procedures for hand fabrication of an electrode set, implantation of electrodes in the same surgery as headplate implantation, fixation of a connector on the headplate, and post-operative recovery care. Following recovery, millisecond-resolution EMG recordings can be obtained during head-fixed behavior for several weeks without noticeable changes in signal quality. These recordings enable precise measurement of forelimb muscle activity alongside in vivo neural recording and/or perturbation to probe mechanisms of motor control in mice.

Author Spotlight: Investigating Mouse Motor Cortex Interactions from Muscle Activity to Neural Dynamics

This protocol describes the hand fabrication and surgical implantation of electromyographic (EMG) electrodes in the forelimb muscles of mice to record muscle activity during head-fixed behavior experiments.

Powerful genetic and molecular tools available in mouse systems neuroscience research have enabled researchers to interrogate motor system function with ...

Open&amp;#45;Source Implant for Multi&amp;#45;Region Electrophysiological Monitoring in Rats

The TD Drive: A Parametric, Open-Source Implant for Multi&#45;Area Electrophysiological Recordings in Behaving and Sleeping Rats

Intricate interactions between multiple brain areas underlie most functions attributed to the brain. The process of learning, as well as the formation and consolidation of memories, are two examples that rely heavily on functional connectivity across the brain. In addition, investigating hemispheric similarities and/or differences goes hand in hand with these multi-area interactions. Electrophysiological studies trying to further elucidate these complex processes thus depend on recording brain activity at multiple locations simultaneously and often in a bilateral fashion. Presented here is a 3D-printable implant for rats, named TD Drive, capable of symmetric, bilateral wire electrode recordings, currently in up to ten distributed brain areas simultaneously. The open-source design was created employing parametric design principles, allowing prospective users to easily adapt the drive design to their needs by simply adjusting high-level parameters, such as anterior-posterior and mediolateral coordinates of the recording electrode locations. The implant design was validated in n = 20 Lister Hooded rats that performed different tasks. The implant was compatible with tethered sleep recordings and open field recordings (Object Exploration) as well as wireless recording in a large maze using two different commercial recording systems and headstages. Thus, presented here is the adaptable design and assembly of a new electrophysiological implant, facilitating fast preparation and implantation.

Author Spotlight: Deciphering Memory and Learning Through Neural Implants for Multi&amp;#45;Region Brain Studies

Here, we present a unique, 3D-printable implant for rats, named TD Drive, capable of symmetric, bilateral wire electrode recordings, currently in up to ten distributed brain areas simultaneously.

Intricate interactions between multiple brain areas underlie most functions attributed to the brain. The process of learning, as well as the formation and ...