We thank Prof. Christine Winter, Julia Klein, Alexandra de Francisco and Yolanda Sierra for their invaluable support in the optimization of the methodology here described.&#160;MLS was supported by the&#160;Ministerio de Ciencia e Innovaci&#243;n, Instituto de Salud Carlos III (project number PI17/01766&#160;and grant number BA21/0030)&#160;co- financed by European Regional Development Fund (ERDF), &#34;A way to make Europe&#34;; CIBERSAM (project number CB07/09/0031); Delegaci&#243;n del Gobierno para el Plan Nacional sobre Drogas (project number 2017/085); Fundaci&#243;n Mapfre; and Fundaci&#243;n Alicia Koplowitz.&#160;MCV was supported by Fundaci&#243;n Tatiana P&#233;rez de Guzm&#225;n el Bueno as scholarship holder of this institution, and EU Joint Programme - Neurodegenerative Disease Research (JPND). DRM was supported by Consejer&#237;a de Educaci&#243;n e Investigaci&#243;n, Comunidad de Madrid, co-funded by European Social Fund &#34;Investing in your future&#34; (grant number PEJD-2018-PRE/BMD-7899). NLR was supported by Instituto de Investigaci&#243;n Sanitaria Gregorio Mara&#241;&#243;n, &#34;Programa Intramural de Impulso a la I+D+I 2019&#34;. MD work was supported by Ministerio de Ciencia e Innovaci&#243;n&#160;(MCIN) and Instituto de Salud Carlos III (ISCIII) (PT20/00044).&#160;The CNIC is supported by the Instituto de Salud Carlos III (ISCIII), the Ministerio de Ciencia e Innovaci&#243;n (MCIN) and the Pro CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505).

Experimental animal procedures were conducted according to the European Communities Council Directive 2010/63/EU, and approved by the Ethics Committee for Animal Experimentation of the Hospital Gregorio Mara&#241;&#243;n. A graphical summary of the experimental protocol is shown in Figure 1A.
1. Brain target localization by in vivo neuroimaging
<ol>
	<li>Animal preparation 
	NOTE: Male Wistar rats of ~300 g were used.
	<ol>
		<li>Place the ...

<ol>
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Considerations in special situations.</a> Spanish Journal of Anesthesiology and Resuscitation. 60 (7), 392-398 (2013).</li><li>Casali, 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=State+of+the+art+of+18F-FDG+PET/CT+application+in+inflammation+and+infection:+a+guide+for+image+acquisition+and+interpretation.">State of the art of 18F-FDG PET/CT application in inflammation and infection: a guide for image acquisition and interpretation.</a> Clinical and Translational Imaging. 9 (4), 299-339 (2021).</li><li>Gonzalez-Escamilla, G., Muthuraman, M., Ciolac, D., Coenen, V. 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The authors declare that there are no conflicts of interest in connection with this article.

Given the advances in the understanding of brain function and the neural networks involved in the pathophysiology of neuropsychiatric disorders, more and more research is recognizing the potential of DBS in a wide range of neurologically-based pathologies2. However, the mechanism of action of this therapy remains unclear. Several theories have attempted to explain the effects obtained in specific pathological and stimulation circumstances, but the heterogeneity of the proposed studies makes it ver...

The term neurostimulation encompasses a number of different techniques aimed at stimulating the nervous system with a therapeutic objective1. Among them, deep brain stimulation (DBS) stands out as one of the most widespread neurostimulation strategies in clinical practice. DBS consists of the stimulation of deep brain nuclei with electrical pulses delivered by a neurostimulator, implanted directly into the patient&#39;s body, through electrodes placed into the brain target to be modulated by stereotactic surgery. The number of articles evaluating the feasibility of DBS application in different neurological and psychiatric disorders is continuously growing2, although only some of them have been approved by the Food and Drug Association&#160;(FDA) (i.e., essential tremor, Parkinson&#39;s disease, dystonia, obsessive-compulsive disorder, and medically refractory epilepsy)3. Furthermore, a large number of brain targets and stimulation protocols are under research for DBS treatment of many more pathologies than officially approved, but none of them are considered definitive. These inconsistencies in DBS research and clinical procedures may in part be due to a lack of full understanding of its mechanism of action4. Therefore, huge efforts are being made to decipher the in vivo effects of DBS on brain dynamics, as every advance, however small, will help refine DBS protocols for greater therapeutic success.
In this context, molecular imaging techniques open a direct window to observe in vivo neuromodulatory effects of DBS. These approaches provide the opportunity not only to determine the impact of DBS while it is being applied but also to unravel the nature of its consequences, prevent undesired side effects and clinical improvement, and even adapt stimulation parameters to the patient&#39;s needs5. Among these methods, positron emission tomography (PET) using 2-deoxy-2-[18F]fluoro-D-glucose (FDG) is of particular interest because it provides specific and real-time information on the activation state of different brain regions6. Specifically, FDG-PET imaging provides an indirect evaluation of neural activation based on the physiological principle of metabolic coupling between neurons and glial cells6. In this sense, several clinical studies have reported DBS-modulated brain activity patterns using FDG-PET (see3 for review). Nevertheless, clinical studies easily incur several drawbacks when focusing on patients, such as heterogeneity or recruitment difficulties, which strongly limit their research potential6. This context leads researchers to use animal models of human conditions to evaluate biomedical approaches before their clinical translation or, if already applied in clinical practice, to explain the physiological origin of therapeutic benefits or side effects. Thus, despite the large distances between human pathology and the modeled condition in laboratory animals, these preclinical approaches are essential for a safe and effective transition into clinical practice.
This manuscript describes an experimental DBS protocol for murine models, combined with a longitudinal FDG-PET study, in order to assess the acute consequences of DBS on brain metabolism. The outcomes obtained with this protocol may help to unravel the intricate modulatory patterns induced on brain activity by DBS. Therefore, a suitable experimental strategy to examine in vivo the consequences of stimulation is provided, allowing clinicians to anticipate therapeutic effects under specific circumstances and then adapt stimulation parameters to the patient&#39;s needs.

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	<tbody>
		<tr>
			<td>7-Tesla Biospec 70/20 scanner</td>
			<td>Bruker, Germany</td>
			<td>SN0021</td>
			<td>MRI scanner for small animal imaging</td>
		</tr>
		<tr>
			<td>Betadine</td>
			<td>Meda Pharma S.L., Spain</td>
			<td>644625.6</td>
			<td>Iodine solution (iodopovidone)</td>
		</tr>
		<tr>
			<td>Beurer IL 11</td>
			<td>Beurer</td>
			<td>SN87318</td>
			<td>Infra-red light</td>
		</tr>
		<tr>
			<td>Bipolar cable 50 cm w/50 cm mesh covering up to 100 cm</td>
			<td>Plastics One, USA</td>
			<td>305-305 (CM)</td>
			<td></td>
		</tr>
		<tr>
			<td>Bipolar cable TT2&#160; 50 cm up to 100 cm</td>
			<td>Plastics One, USA</td>
			<td>305-340/2</td>
			<td>Bipolar cable TT2&#160; 50 cm up to 100 cm</td>
		</tr>
		<tr>
			<td>Buprex</td>
			<td>Schering-Plough, S.A</td>
			<td>961425</td>
			<td>Buprenorphine (analgesic)</td>
		</tr>
		<tr>
			<td>Ceftriaxona Reig Jofr&#233; 1g IM</td>
			<td>Laboratorio Reig Jofr&#233; S.A., Spain</td>
			<td>624239.1</td>
			<td>Ceftriaxone (antibiotic)</td>
		</tr>
		<tr>
			<td>Commutator</td>
			<td>Plastics One, USA</td>
			<td>SL2+2C</td>
			<td>4 Channel Commutator for DBS</td>
		</tr>
		<tr>
			<td>Concentric bipolar platinum-iridium electrodes</td>
			<td>Plastics One, USA</td>
			<td>MS303/8-AIU/Spc</td>
			<td>Electrodes for DBS</td>
		</tr>
		<tr>
			<td>Driller</td>
			<td>Bosh</td>
			<td>T58704</td>
			<td>Driller</td>
		</tr>
		<tr>
			<td>FDG</td>
			<td>Curium Pharma Spain S.A., Spain</td>
			<td>-----</td>
			<td>2-[18F]fluoro-2-deoxy-D-glucose (PET radiotracer)</td>
		</tr>
		<tr>
			<td>Heating pad</td>
			<td>DAGA, Spain</td>
			<td>23115</td>
			<td>Heating pad</td>
		</tr>
		<tr>
			<td>Ketolar</td>
			<td>Pfizer S.L., Spain</td>
			<td>776211.9</td>
			<td>Ketamine (anesthetic drug)</td>
		</tr>
		<tr>
			<td>Lipolasic 2 mg/g</td>
			<td>Bausch &#38; Lomb S.A, Spain</td>
			<td>65277</td>
			<td>Ophthalmic lubricating gel</td>
		</tr>
		<tr>
			<td>MatLab R2021a</td>
			<td>The MathWorks, Inc</td>
			<td></td>
			<td>Support software for SPM12</td>
		</tr>
		<tr>
			<td>MRIcro</td>
			<td>McCausland Center for Brain Imaging,&#160; University of South Carolina, USA</td>
			<td>v2.1.58-0</td>
			<td>Software for imaging preprocessing and analysis</td>
		</tr>
		<tr>
			<td>Multimodality Workstation (MMWKS)</td>
			<td>BiiG, Spain</td>
			<td></td>
			<td>Software for imaging processing and analysis</td>
		</tr>
		<tr>
			<td>Omicrom VISION VET</td>
			<td>RGB Medical Devices, Spain</td>
			<td>731100 ReV B</td>
			<td>Cardiorrespiratory monitor for small imaging</td>
		</tr>
		<tr>
			<td>Prevex Cotton buds</td>
			<td>Prevex, Finland</td>
			<td>-----</td>
			<td>Cotton buds</td>
		</tr>
		<tr>
			<td>Sevorane</td>
			<td>AbbVie Spain, S.L.U, Spain</td>
			<td>673186.4</td>
			<td>Sevoflurane (inhalatory anesthesia)</td>
		</tr>
		<tr>
			<td>Small screws</td>
			<td>Max Witte GmbH</td>
			<td>1,2 x 2 DIN 84 A2</td>
			<td>Small screws</td>
		</tr>
		<tr>
			<td>Standard U-Frame Stereotaxic Instrument for Rat, 18&#176; Ear Bar</td>
			<td>Harvard Apparatus, USA</td>
			<td>75-1801</td>
			<td>Two-arms Stereotactic frame for rat</td>
		</tr>
		<tr>
			<td>Statistical Parametric Mapping (SPM12)</td>
			<td>The Wellcome Center for Human Neuroimaging, UCL Queen Square Institute of Neurology, UK</td>
			<td>SPM12</td>
			<td>Software for voxel-wise imaging analysis</td>
		</tr>
		<tr>
			<td>STG1004</td>
			<td>Multi Channel Systems GmbH, Germany</td>
			<td>STG1004</td>
			<td>Isolated stimulator</td>
		</tr>
		<tr>
			<td>SuperArgus PET/CT scanner</td>
			<td>Sedecal, Spain</td>
			<td>S0026403</td>
			<td>NanoPET/CT scanner for small animal imaging</td>
		</tr>
		<tr>
			<td>Suture thread with needle, 1/&#186;</td>
			<td>Lorca Mar&#237;n S.A., Spain</td>
			<td>55325</td>
			<td>Braided natural silk non-absorbable suture 1/0, with triangle needle</td>
		</tr>
		<tr>
			<td>Technovit 4004 (powder and liquid)</td>
			<td>Kulzer Technique, Germany</td>
			<td>64708471; 64708474</td>
			<td>Acrylic dental cement for craniotomy tap</td>
		</tr>
		<tr>
			<td>Wistar rats (Rattus norvergicus)</td>
			<td>Charles River, Spain</td>
			<td>animal facility</td>
			<td>Animal model used</td>
		</tr>
		<tr>
			<td>Xylagesic</td>
			<td>Laboratorios Karizoo, A.A, Spain</td>
			<td>572599-4</td>
			<td>Xylazine (anesthetic drug)</td>
		</tr>
		<tr>
			<td></td>
			<td>Normon S.A., Spain</td>
			<td>602910</td>
			<td>Mepivacaine in gel for topical use</td>
		</tr>
	</tbody>
</table>

in vivo positron emission tomography to reveal activity patterns induced by deep brain stimulation in rats

Deep brain stimulation (DBS) is an invasive neurosurgical technique based on the application of electrical pulses to brain structures involved in the patient&#39;s pathophysiology. Despite the long history of DBS, its mechanism of action and appropriate protocols remain unclear, highlighting the need for research aiming to solve these enigmas. In this sense, evaluating the in vivo effects of DBS using functional imaging techniques represents a powerful strategy to determine the impact of stimulation on brain dynamics. Here, an experimental protocol for preclinical models (Wistar rats), combined with a longitudinal study [18F]-fluorodeoxyclucose positron emission tomography (FDG-PET), to assess the acute consequences of DBS on brain metabolism is described. First, animals underwent stereotactic surgery for bilateral implantation of electrodes into the prefrontal cortex. A post-surgical computerized tomography (CT) scan of each animal was acquired to verify electrode placement. After one week of recovery, a first static FDG-PET of each operated animal without stimulation (D1) was acquired, and two days later (D2), a second FDG-PET was acquired while animals were stimulated. For that, the electrodes were connected to an isolated stimulator after administering FDG to the animals. Thus, animals were stimulated during the FDG uptake period (45 min), recording the acute effects of DBS on brain metabolism. Given the exploratory nature of this study, FDG-PET images were analyzed by a voxel-wise approach based on a paired T-test between D1 and D2 studies. Overall, the combination of DBS and imaging studies allows describing the neuromodulation consequences on neural networks, ultimately helping to unravel the conundrums surrounding DBS.

The animals were sacrificed using CO2&#160;at the end of the study or when the animal&#8217;s welfare was compromised. An example of a complete PET/CT study from an operated animal is shown in Figure 3. Thus, the electrode inserted into the rat brain can be clearly observed in the CT image shown in Figure 3A. This imaging modality provides good anatomical information and facilitates the registration of FDG-PET images, given that functional modalities ...

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In vivo Positron Emission Tomography to Reveal Activity Patterns Induced by Deep Brain Stimulation in Rats

We describe a preclinical experimental method to evaluate metabolic neuromodulation induced by acute deep brain stimulation with in vivo FDG-PET. This manuscript includes all experimental steps, from stereotaxic surgery to the application of the stimulation treatment and the acquisition, processing, and analysis of PET images.

In vivo Positron Emission Tomography to Reveal Activity Patterns Induced by Deep Brain Stimulation in Rats

Deep brain stimulation (DBS) is an invasive neurosurgical technique based on the application of electrical pulses to brain structures involved in the ...

This protocol allows to study the stimulation consequences on neural networks helping to unravel the enigma surrounding DBS. And to determine the impact of a stimulation on brain dynamics. The main advantage of using FD repair during a stimulation is that we can visualize the in vivo consequences of the acute stimulation on brain dynamics and then refine in vivo the stimulation protocols.This method is of particular relevance in the fields of neurology and psychiatry. As it is in these medical specialties in which DBS has its major impact as an anthroponotic strategy. To begin, lay the anesthetized animal supine on the CT bed.For CT imaging, secure the face mask or nose cone to the rat. Locate the head in the center of the field of view of the CT scanner. Proceed to acquire the CT image using acquisition parameters according to the scanner's specifications.For MR Imaging, lay the animal supine on the MRI bed. To avoid movements during MRI acquisition, secure the head to a stereotactic frame placed on the scanner bed. Also, secure the rest of the rat body with silk tape.Once the position is correct, acquire the MRI image. Use an image processing software to spatially normalize CT and MRI using an automatic rigid registration algorithm based on mutual information. Localize the bregma line in the co-registered image.And measure the distance in the AP, ML, and DV access from bregma to the medial prefrontal cortex according to the Paxinos and Watson Rat Brain Atlas. Shave the area between the ears and the eyes. Place the animal in the prone position on the stereotactic frame.Ensure immobility of the head by using the rat ear bars. Be careful not to insert the ear bars too deep as this may damage the eardrum. Use the head holding adapter for rats to maintain the animal in the correct position during the surgery.Apply Athymic lubricating gel to the rat eyes to prevent dryness during surgery and cover them with sterile gauze. Make a longitudinal incision in the skin overlying the skull between the ears. Extending 1.5 to two centimeters from lambda to bregma.Expose the skull with the help of two or three clamps. Remove the periosteum with scissors and clean the blood with saline solution To expose bregma and the sagittal sutures. Remove the excess saline solution with gauze.Before positioning the electrodes, straighten them with plastic tweezers to ensure the correct placement during the surgery. Place one electrode on the holder of the right arm of the stereotactic frame. Move the right arm holding the electrode through the stereotactic frame.And place the tip of the electrode exactly over bregma. Try to bring the electrode tip as close as possible to the skull without touching it To avoid electrode deformation. Note the resulting coordinates for bregma provided by the stereotaxic frame.Using a surgical pen, make a mark on the skull indicating the initial position of the electrode. Move the holder to the AP and ML coordinates obtained earlier. And make a mark on the skull with a surgical pen indicating the position of the electrode target.Remove the right arm of the stereotactic frame holding the electrode. Be careful not to touch anything with the electrode. Using a small electric drill, make a hole through the skull in the target position until the dura is visible.Use a cotton bud to stop the bleeding. Drill four holes along the skull to place four screws. To increase the dental cement surface area and locate the ground.Then attach the screws. Locate the right arm of the stereotactic frame with the right electrode. Move the arm to the calculated position which should coincide with the hole.Then lower the electrode until it touches the dura mater. This position will serve as zero level in the DV direction. Using the DV coordinates obtained earlier, insert the tip of the electrode in the DV direction.Attach the ground to one of the screws closest to the electrode and apply dental cement around the electrode and screws. Repeat the same electrode placement procedure for the other hemisphere of the brain. Apply more dental cement to form a cap without covering the electrode and wait until it hardens.Use iodopovidone solution to disinfect the surgical area. Remove the rat from the stereotactic frame and proceed with CT imaging as demonstrated earlier to evaluate the correct placement of the electrodes. Fast the rat for eight to 12 hours prior to each PET scan.Fill a 27 gauge syringe with approximately 37 megabecquerel of the FDG solution in the least possible volume as measured in an activimeter. Place a heating pad under the animal's tail or use infrared light to dilate the tail veins. Inject the FDG solution through one of the lateral tail veins.Place the animal back in the cage and allow 45 minutes for radio tracer uptake before initiating the image acquisition session. For the D2 study, delivered DBS during the FDG uptake period. Prepare the isolated stimulator and the required wires in a vast and quiet room with enough space for the animal cages and minimal influence of potentially disturbing stimuli.Connect the stimulation wires to the swivels to allow animals to freely move within the cages and to the stimulator. Set the stimulation parameters as described in the text manuscript. Use an oscilloscope to check the current mode, frequency, and pulse width.Confirm the biphasic wave form with a rectangular pulse shape. The CT image clearly visualized the electrode inserted into the rat brain. The imaging modality used in this study also provided good anatomical information and facilitated the registration of FDG-PET images.A fused PET-CT image of the same animal spatially registered to the same stereotaxic space. The brain metabolic differences were observed between PET sessions as T-maps superimposed on sequential one millimeter brain slices from an MRI registered to the reference CT image. These differences consisted of increases and decreases in FDG uptake shown as warm and cold colors respectively.A detailed summary of the statistical results obtained from the analysis indicated the modulated brain region and the brain hemisphere in which the modulation was observed. The T statistic, the cluster size, the direction of modulation, and P-values obtained at peak and cluster levels. It is crucial to maintain an adequate aesthetic level and of the head during the surgery.Moreover, coordinate calculation and a straightness of the electrodes are essential. New operators are advised to be meticulous and follow all the steps. After completing the whole procedure animals can be subjected to behavioral test to evaluate the stimulation impact on different cognitive domains.In addition, a number of image studies can be performed to assess the DBS consequences at the cellular level.

in-vivo-positron-emission-tomography-to-reveal-activity-patterns

Research

JoVE Journal

Neuroscience

2.0K visualizações.  Centro Nacional de Investigaciones Cardiovasculares (CNIC). Este protocolo permite estudar as consequências da estimulação em redes neurais, ajudando a desvendar o enigma em torno da DBS. E para determinar o impacto de uma estimulação na dinâmica do cérebro. A principal vantagem de usar o reparo de FD durante uma estimulação é que podemos visualizar as consequências in vivo da estimulação aguda na dinâmica cerebral e, em seguida, refinar in vivo os protocolos de estimulação.Este método é de particular relevância nos campos da...