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.

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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 ...

Abdominal VNS for Treating Inflammatory Conditions in Rat Models

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

Author Spotlight: Exploring Abdominal VNS for Inflammatory Conditions

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

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

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

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

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

Open&#45;Source Implant for Multi&#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

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

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