This work was supported by the LabEx TRAIL grant, reference ANR-10-LABX-57, and a French-Swiss ANR-FNS grant reference ANR-15- CE37-0012. The authors thank Aur&#233;lien Trotier for his technical support.

All animal procedures were conducted in accordance with the Animal Experimentation Guidelines of the European Communities Council Directive of November 24, 1986 (86/609/EEC). The protocol met the ethical guidelines of the French Ministry of Agriculture and Forests and was approved by the local ethics committees (Comit&#233; d&#39;&#233;thique pour L&#39;exp&#233;rimentation Animale Bordeaux n&#176;50112090-A).
NOTE: During the MR measurements, an adequate level of anesthesia and physiological ...

<ol>
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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glutamate+uptake+into+astrocytes+stimulates+aerobic+glycolysis:+a+mechanism+coupling+neuronal+activity+to+glucose+utilization.">Glutamate uptake into astrocytes stimulates aerobic glycolysis: a mechanism coupling neuronal activity to glucose utilization.</a> Proceedings of the National Academy of Sciences of the United States of America. 91, 10625-10629 (1994).</li><li>Cholet, N., 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=Local+injection+of+antisense+oligonucleotides+targeted+to+the+glial+glutamate+transporter+GLAST+decreases+the+metabolic+response+to+somatosensory+activation.">Local injection of antisense oligonucleotides targeted to the glial glutamate transporter GLAST decreases the metabolic response to somatosensory activation.</a> Journal of Cerebral Blood Flow &amp; Metabolism. 21, 404-412 (2001).</li><li>Voutsinos-Porche, B., 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=Glial+Glutamate+Transporters+Mediate+a+Functional+Metabolic+Crosstalk+between+Neurons+and+Astrocytes+in+the+Mouse+Developing+Cortex.">Glial Glutamate Transporters Mediate a Functional Metabolic Crosstalk between Neurons and Astrocytes in the Mouse Developing Cortex.</a> Neuron. 37, 275-286 (2003).</li><li>Zimmer, E. 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=[18F]FDG+PET+signal+is+driven+by+astroglial+glutamate+transport.">[18F]FDG PET signal is driven by astroglial glutamate transport.</a> Nature Neuroscience. 20 (3), 393-395 (2017).</li><li>Haiss, F., 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=Improved+in+vivo+two-photon+imaging+after+blood+replacement+by+perfluorocarbon.">Improved in vivo two-photon imaging after blood replacement by perfluorocarbon.</a> The Journal of Physiology. , (2009).</li><li>Mullins, P. 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S., Durif, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+of+the+brain+hemodynamic+responses+to+sensorimotor+stimulation+in+a+rodent+model:+A+BOLD+fMRI+study.">Mapping of the brain hemodynamic responses to sensorimotor stimulation in a rodent model: A BOLD fMRI study.</a> PLoS One. 12, e0176512 (2017).</li><li>Heinke, W., Koelsch, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effects+of+anesthetics+on+brain+activity+and+cognitive+function.">The effects of anesthetics on brain activity and cognitive function.</a> Current Opinion in Anesthesiology. 18, 625-631 (2005).</li><li>Horn, T., Klein, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lactate+levels+in+the+brain+are+elevated+upon+exposure+to+volatile+anesthetics:+a+microdialysis+study.">Lactate levels in the brain are elevated upon exposure to volatile anesthetics: a microdialysis study.</a> Neurochemistry International. 57, 940-947 (2010).</li><li>Boretius, S., 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=Halogenated+volatile+anesthetics+alter+brain+metabolism+as+revealed+by+proton+magnetic+resonance+spectroscopy+of+mice+in+vivo.">Halogenated volatile anesthetics alter brain metabolism as revealed by proton magnetic resonance spectroscopy of mice in vivo.</a> Neuroimage. 69, 244-255 (2013).</li><li>Sinclair, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+of+the+physiological+effects+of+alpha2-agonists+related+to+the+clinical+use+of+medetomidine+in+small+animal+practice.">A review of the physiological effects of alpha2-agonists related to the clinical use of medetomidine in small animal practice.</a> Canadian Veterinary Journal. 44, 885-897 (2003).</li><li>Weber, 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=A+fully+noninvasive+and+robust+experimental+protocol+for+longitudinal+fMRI+studies+in+the+rat.">A fully noninvasive and robust experimental protocol for longitudinal fMRI studies in the rat.</a> Neuroimage. 29, 1303-1310 (2006).</li><li>Hartmann, M. J., Johnson, N. J., Towal, R. B., Assad, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+characteristics+of+rat+vibrissae:+resonant+frequencies+and+damping+in+isolated+whiskers+and+in+the+awake+behaving+animal.">Mechanical characteristics of rat vibrissae: resonant frequencies and damping in isolated whiskers and in the awake behaving animal.</a> The Journal of Neuroscience. 23, 6510-6519 (2003).</li><li>Prichard, 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=Lactate+rise+detected+by+1H+NMR+in+human+visual+cortex+during+physiologic+stimulation.">Lactate rise detected by 1H NMR in human visual cortex during physiologic stimulation.</a> Proceedings of the National Academy of Sciences of the United States of America. 88, 5829-5831 (1991).</li><li>Sappey-Marinier, D., 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=Effect+of+photic+stimulation+on+human+visual+cortex+lactate+and+phosphates+using+1H+and+31P+magnetic+resonance+spectroscopy.">Effect of photic stimulation on human visual cortex lactate and phosphates using 1H and 31P magnetic resonance spectroscopy.</a> Journal of Cerebral Blood Flow &amp; Metabolism. 12, 584-592 (1992).</li><li>Mazuel, L., 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=A+neuronal+MCT2+knockdown+in+the+rat+somatosensory+cortex+reduces+both+the+NMR+lactate+signal+and+the+BOLD+response+during+whisker+stimulation.">A neuronal MCT2 knockdown in the rat somatosensory cortex reduces both the NMR lactate signal and the BOLD response during whisker stimulation.</a> PLoS One. 12, e0174990 (2017).</li><li>Castellano, G., 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=NAA+and+NAAG+variation+in+neuronal+activation+during+visual+stimulation.">NAA and NAAG variation in neuronal activation during visual stimulation.</a> Brazilian Journal of Medical and Biological Research. 45, 1031-1036 (2012).</li><li>Sarchielli, 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=Functional+1H-MRS+findings+in+migraine+patients+with+and+without+aura+assessed+interictally.">Functional 1H-MRS findings in migraine patients with and without aura assessed interictally.</a> Neuroimage. 24, 1025-1031 (2005).</li><li>Baslow, M. H., Hrabe, J., Guilfoyle, D. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+relationship+between+neurostimulation+and+N-acetylaspartate+metabolism+in+the+human+visual+cortex:+evidence+that+NAA+functions+as+a+molecular+water+pump+during+visual+stimulation.">Dynamic relationship between neurostimulation and N-acetylaspartate metabolism in the human visual cortex: evidence that NAA functions as a molecular water pump during visual stimulation.</a> Journal of Molecular Neuroscience. 32, 235-245 (2007).</li><li>Mangia, S., Tkac, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+relationship+between+neurostimulation+and+N-acetylaspartate+metabolism+in+the+human+visual+cortex:+evidence+that+NAA+functions+as+a+molecular+water+pump+during+visual+stimulation.">Dynamic relationship between neurostimulation and N-acetylaspartate metabolism in the human visual cortex: evidence that NAA functions as a molecular water pump during visual stimulation.</a> Journal of Molecular Neuroscience. 35, 245-248 (2008).</li><li>Baslow, M. H., Hrabal, R., Guilfoyle, D. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Response+of+the+authors+to+the+Letter+by+Silvia+Mangia+and+Ivan+Tkac.">Response of the authors to the Letter by Silvia Mangia and Ivan Tkac.</a> Journal of Molecular Neuroscience. 35, 247-248 (2008).</li><li>Barros, L. F., Weber, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CrossTalk+proposal:+an+important+astrocyte-to-neuron+lactate+shuttle+couples+neuronal+activity+to+glucose+utilisation+in+the+brain.">CrossTalk proposal: an important astrocyte-to-neuron lactate shuttle couples neuronal activity to glucose utilisation in the brain.</a> The Journal of Physiology. 596, 347-350 (2018).</li><li>Bak, L. K., Walls, A. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CrossTalk+opposing+view:+lack+of+evidence+supporting+an+astrocyte-to-neuron+lactate+shuttle+coupling+neuronal+activity+to+glucose+utilisation+in+the+brain.">CrossTalk opposing view: lack of evidence supporting an astrocyte-to-neuron lactate shuttle coupling neuronal activity to glucose utilisation in the brain.</a> The Journal of Physiology. 596, 351-353 (2018).</li></ol>

The barrel cortex, also called S1BF for the somatosensory cortex or barrel field, is a region within the cortical layer IV that can be observed using cytochrome c oxidase staining9, and its organization is well known since it has been largely described10,11. One vibrissa is connected to one barrel, in which around 19,000 neurons are organized in a column12. The whisker-to-barrel cortex pathway has several advantages...

The brain possesses intrinsic mechanisms that allow the regulation of its major substrate (i.e., glucose), both for its contribution and its utilization, depending on variations in local cerebral activity. Although glucose is the main energy substrate for the brain, experiments performed in recent years have shown that lactate, which is produced by the astrocytes, could be an efficient energy substrate for the neurons. This raises the hypothesis of a lactate shuttle between astrocytes and neurons1. Known as ANLS, for astrocyte-neuron lactate shuttle2, the theory is still highly debated but has led to the proposal that glucose, rather than going directly into neurons, may enter the astrocytes, where it is metabolized into lactate, a metabolite that is, then, transferred to the neurons, which use it as efficient energy substrate. If such a shuttle exists in vivo, it would have several important consequences, both for the understanding of basic techniques in functional cerebral imaging (positron emission tomography [PET]) and for deciphering the metabolic alterations observed in brain pathologies.
To study brain metabolism and, particularly, metabolic interactions between neurons and astrocytes, four main techniques are available (not including micro-/nanosensors): autoradiography, PET, two-photon fluorescent confocal microscopy, and MRS. Autoradiography was one of the first methods proposed and provides images of the regional accumulation of radioactive 14C-2-deoxyglucose in brain slices, while PET yields in vivo images of the regional uptake of radioactive 18F-deoxyglucose. They both have the disadvantage of using irradiative molecules while producing low-spatial resolution images. Two-photon microscopy provides cellular resolution of fluorescent probes, but light scattering by tissue limits the imaging depth. These three techniques have been used previously to study neuroenergetics in rodents during whisker stimulation3,4,5,6. In vivo MRS has the dual advantage of being noninvasive and nonradioactive, and any brain structure can be explored. Moreover, MRS can be performed during neuronal activation, a technique called functional MRS (fMRS), which has been developed very recently in rodents7. Therefore, a protocol to monitor brain metabolism during cerebral activity by 1H-MRS in vivo and noninvasively is proposed. The procedure is described in adult healthy rats with brain activation obtained by an air-puff whisker stimulation performed directly in a 7 T magnetic resonance (MR) imager but may be adapted in genetically modified animals, as well as in any pathological condition.

<table>
	<tbody>
		<tr>
			<td>0.5 mL syringe with needle</td>
			<td>Becton, Dickinson and Company, USA</td>
			<td>2020-10</td>
			<td>0.33 mm (29 G) x 12.7 mm</td>
		</tr>
		<tr>
			<td>1H spectroscopy surface coil</td>
			<td>Bruker, Ettlingen, Germany</td>
			<td>T116344</td>
			<td></td>
		</tr>
		<tr>
			<td>7T Bruker Biospec system</td>
			<td>Bruker, Ettlingen, Germany</td>
			<td>70/20 USR</td>
			<td></td>
		</tr>
		<tr>
			<td>Arduino Uno based pulsing device</td>
			<td>custom made</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Atipamezole</td>
			<td>V&#233;toquinol, S.A., France</td>
			<td>V8335602</td>
			<td>Antisedan, 4.28 mg</td>
		</tr>
		<tr>
			<td>Breathing mask</td>
			<td>custom made</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Eye ointment</td>
			<td>TVM laboratoire, France</td>
			<td>40365</td>
			<td>Ocry gel 10 g</td>
		</tr>
		<tr>
			<td>Induction chamber</td>
			<td>custom made</td>
			<td></td>
			<td>30x17x15 cm</td>
		</tr>
		<tr>
			<td>Inlet flexible pipe</td>
			<td>Gardena, Germany</td>
			<td>1348-20</td>
			<td>4.6-mm diameter, 3m long</td>
		</tr>
		<tr>
			<td>Isoflurane pump, Model 100 series vaporizer, classic T3</td>
			<td>Surgivet, Harvard Apparatus</td>
			<td>WWV90TT</td>
			<td>from OH 43017, U.S.A</td>
		</tr>
		<tr>
			<td>Isoflurane, liquid for inhalation</td>
			<td>Vertflurane, Virbac, France</td>
			<td>QN01AB06</td>
			<td>1000 mg/mL</td>
		</tr>
		<tr>
			<td>KD Scientific syringe pump</td>
			<td>KD sientific, Holliston, USA</td>
			<td>Legato 110</td>
			<td></td>
		</tr>
		<tr>
			<td>LCModel software</td>
			<td>LCModel Inc., Ontario, Canada</td>
			<td>6.2</td>
			<td></td>
		</tr>
		<tr>
			<td>Medetomidine hydrochloride</td>
			<td>V&#233;toquinol, S.A., France</td>
			<td>QN05CM91</td>
			<td>Domitor, 1 mg/mL</td>
		</tr>
		<tr>
			<td>Micropore roll of adhesive plaster</td>
			<td>3M micropore, Minnesota, United States</td>
			<td>MI912</td>
			<td></td>
		</tr>
		<tr>
			<td>Micropore roll of adhesive plaster</td>
			<td>3M micropore, Minnesota, United States</td>
			<td>MI925</td>
			<td></td>
		</tr>
		<tr>
			<td>Monitoring system of physiologic parameter</td>
			<td>SA Instruments, Inc, Stony Brook, NY, USA</td>
			<td>Model 1025</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Fresenius Kabi, Germany</td>
			<td>B05XA03</td>
			<td>0.9 % 250 mL</td>
		</tr>
		<tr>
			<td>Outlet flexible pipe</td>
			<td>Gardena, Germany</td>
			<td>1348-20</td>
			<td>4.6-mm diameter, 4m long</td>
		</tr>
		<tr>
			<td>Paravision software</td>
			<td>Bruker, Ettlingen, Germany</td>
			<td>6.0.1</td>
			<td></td>
		</tr>
		<tr>
			<td>Peripheral intravenous catheter</td>
			<td>Terumo, Shibuya, Tokyo, Japon</td>
			<td>SP500930S</td>
			<td>22 G x 1&#34;, 0.85x25 mm, 35 mL/min</td>
		</tr>
		<tr>
			<td>Rat head coil</td>
			<td>Bruker, Ettlingen, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sodic heparin, injectable solution</td>
			<td>Choai, Sanofi, Paris, France</td>
			<td>B01AB01</td>
			<td>5000 IU/mL</td>
		</tr>
		<tr>
			<td>Solenoid control valves, plunger valve 2/2 way direct-acting</td>
			<td>Burkert, Germany</td>
			<td>3099939</td>
			<td>Model type 6013</td>
		</tr>
		<tr>
			<td>Terumo 2 ml syringe</td>
			<td>Terumo, Shibuya, Tokyo, Japon</td>
			<td>SY243</td>
			<td>with 21 g x 5/8&#34; needle</td>
		</tr>
		<tr>
			<td>Terumo 5 mL syringe</td>
			<td>Terumo, Shibuya, Tokyo, Japon</td>
			<td>05SE1</td>
			<td></td>
		</tr>
		<tr>
			<td>Wistar RJ-Han rats</td>
			<td>Janvier Laboratories, France</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

functional magnetic resonance spectroscopy at 7 t in the rat barrel cortex during whisker activation

Nuclear magnetic resonance (NMR) spectroscopy offers the opportunity to measure cerebral metabolite contents in vivo and noninvasively. Thanks to technological developments over the last decade and the increase in magnetic field strength, it is now possible to obtain good resolution spectra in vivo in the rat brain. Neuroenergetics (i.e., the study of brain metabolism) and, especially, metabolic interactions between the different cell types have attracted more and more interest in recent years. Among these metabolic interactions, the existence of a lactate shuttle between neurons and astrocytes is still debated. It is, thus, of great interest to perform functional proton magnetic resonance spectroscopy (1H-MRS) in a rat model of brain activation and monitor lactate. However, the methyl lactate peak overlaps lipid resonance peaks and is difficult to quantify. The protocol described below allows metabolic and lactate fluctuations to be monitored in an activated brain area. Cerebral activation is obtained by whisker stimulation and 1H-MRS is performed in the corresponding activated barrel cortex, whose area is detected using blood-oxygen-level-dependent functional magnetic resonance imaging (BOLD fMRI). All steps are fully described: the choice of anesthetics, coils, and sequences, achieving efficient whisker stimulation directly in the magnet, and data processing.

This protocol allows the quantification of metabolite fluctuations during cerebral activation, which is obtained by right whisker stimulation directly in the magnet.
In this study, the overall goal of BOLD fMRI was to check that the whisker stimulation was efficient, to visualize the activated S1BF area, and to correctly locate the voxel for 1H-fMRS. The device built for whisker activation is efficient. Indeed, when r...

Watch this Scientific Journal Video about Functional Magnetic Resonance Spectroscopy at 7 T in the Rat Barrel Cortex During Whisker Activation at JoVE.com

Functional Magnetic Resonance Spectroscopy at 7 T in the Rat Barrel Cortex During Whisker Activation

After checking by blood-oxygen-level-dependent functional magnetic resonance imaging (BOLD fMRI) that the corresponding somatosensory barrel field cortex area (called S1BF) is correctly activated, the main goal of this study is to quantify lactate content fluctuations in the activated rat brains by localized proton magnetic resonance spectroscopy (1H-MRS) at 7 T.

Nuclear magnetic resonance (NMR) spectroscopy offers the opportunity to measure cerebral metabolite contents in vivo and noninvasively. Thanks to ...

This method can help answer key questions in the field of neuro genetics and decipher the metabolic changes that occur between rest and activated states.The main advantage of this technique is to follow this variation in vivo in real time in a non-invasive manner.Notably this technique can be applied to pathological or genetically modified animals, for example to determine the role of a specific protein in metabolic interaction between neurons and lyocells.Begin by placing a breathing sensor on the magnet bed and transferring the rat to the magnet bed in the prone position with its nose in the isoflurane mask and with the breathing sensor located between the rib cage and the magnet bed.Ensure that the right whiskers are free and secure the rat with tape.Use tape to make a sale that traps all of the right whiskers and align the flexible outlet pipe of the air puff system along the rat MRI bed so that the part exiting the tube is perpendicular and about one and a half centimeters from the sale.Then fix the pipe into position with more tape.Next connect the flexible inlet pipe from a compressed air source to a solenoid control valve input and the outlet pipe to the solenoid control valve output, taking care that the solenoid control valve remains outside of the magnet room.Use the transistor transistor-logic port to plug the pulsing device into the solenoid valve and the magnet and configure the device so that the pulsing frequency is eight Hertz, the pulsing time is 20 seconds, and the resting time is 10 seconds.For whisker stimulation place the rat with the brain in an upright position and secure the animal with ear bars.Place the volume array coil above the head and fix the array with tape.Turn on the air puff system to check that the sale moves in the anteroposterior direction with no rotation and no friction.Then switch the air puff system off and place the bed end coil into the center of the magnet.For blood oxygen level dependent functional resonance imaging, check the sale movement again and use a localization sequence to confirm that the rat is well positioned.Drag the localizer sequence tab into the instruction name and click continue.If the location is okay drag the T2 Star FID EPI sequence tab into the instruction name, center the field of view on the middle of the brain, and click adjustment platform to open the edited scan instruction.Then record a B0 map and start the T2 Star FID EPI sequence.Acquire another localization sequence as just demonstrated to compare with the first one and check whether the rat has moved during the T2 Star FID EPI sequence.Then return the bed to its initial position and remove the volume array coil.To process the images open the T2 Star FID EPI file and read the T2 Star FID EPI image in the image display.Open the start-up window of the functional controller and in the processing tab select the functional imaging window.Define the stimulation protocol and select the protocol window, setting the on period to 40 and the off period to 20.Click invert attribution and drag the stimulation state slider to the left to select a value of one.In the pre-processing window set the median filter in plain for pre-processing and the median filter 2D 3D for post-processing.Then click execute.Drag the cursors to adjust the overlay lookup table and visualize the activated brain area.To correctly position the surface coil for proton magnetic resonance spectroscopy or MRS, rotate the head approximately 30 degrees clockwise so that the surface coil can be placed just above the left barrel cortex in a horizontal position and located at the magnet center when inside the magnet.Plug the surface coil and fix the coil into place with tape.Check that the sale can still move correctly when the air puff system is on.Then place the bed into the magnet and check the sale movement again.Confirm the correct position of the animal with the localization sequence as demonstrated and drag the T2-TurboRARE sequence tab into the instruction name window.Then click continue to execute the scan program and to allow the correct localization of the voxel within the somatosensory barrel field cortex.At the end of the scan drag the laser sequence tab into the instruction name window and place the voxel at the center of the somatosensory barrel field cortex area.Click adjustment platform to open the edited scan instruction and click wobble to slightly change the impedance of the receiver coil for tuning.When the tuning is finished, click apply to close the instruction editor and to apply the changes in the edited instruction.Record a B0 map and start the pro diem MRS acquisition during a resting period.Acquire another localization sequence to compare with the first one and confirm that the rat did not move during the laser acquisition.Then turn on the air puff system and use the laser sequence to perform a second proton MRS.Perform a final localization sequence to check whether the rat has moved before returning the bed to its initial position.Then remove the surface coil and return the rat to the bench with monitoring until full recovery.To process the MRS images open the linear combination of model spectra or LC model software and select the appropriate data type and file.Click okay and in the title section manually enter a title and define an adequate parts per milliliter range.Then click run LC model to start the LC model quantification.When right whiskers are stimulated using the homemade air puff system as demonstrated a positive BOLD signal is detected in the left barrel cortex, also called the somatosensory barrel field.Using anatomical magnetic resonance images and a rat brain atlas scheme the activated brain area visualized by BOLD functional MRI allows a voxel to be placed in the somatosensory barrel field area that is activated during the whisker stimulation.When the paradigm for whisker stimulation is turned on an increase in lactate content is observed in the left somatosensory barrel field.To better visualize the metabolic fluctuations between resting and activated periods a spectral subtraction can be performed.From this subtracted spectrum the increase in lactate content with brain activation can be visualized much more easily.For example in this rat the N-Acetylaspartate signal was slightly decreased.While the lactate peak is hardly detected on this in vivo deconvolution spectrum at rest the LC model was able to quantify the peak with a good accuracy and Cram

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Research

JoVE Journal

Neuroscience

8.5K Views.  Centre National de la Recherche Scientifique (CNRS)/Université Bordeaux. This method can help answer key questions in the field of neuro genetics and decipher the metabolic changes that occur between rest and activated states.The main advantage of this technique is to follow this variation in vivo in real time in a non-invasive manner.Notably this technique can be applied to pathological or genetically modified animals, for example to determine the role of a specific protein in metabolic interaction between neurons and lyocells.Begin by placing a breathing sensor ...