Name: functional magnetic resonance spectroscopy at 7 t in the rat barrel cortex during whisker activation
Uploaded: 2019-02-08T14:00:00
Description: Watch this Scientific Journal Video about Functional Magnetic Resonance Spectroscopy at 7 T in the Rat Barrel Cortex During Whisker Activation at JoVE.com

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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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>
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			<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>
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		<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>
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		<tr>
			<td>Arduino Uno based pulsing device</td>
			<td>custom made</td>
			<td></td>
			<td></td>
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			<td>Atipamezole</td>
			<td>V&#233;toquinol, S.A., France</td>
			<td>V8335602</td>
			<td>Antisedan, 4.28 mg</td>
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			<td>Breathing mask</td>
			<td>custom made</td>
			<td></td>
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			<td>Eye ointment</td>
			<td>TVM laboratoire, France</td>
			<td>40365</td>
			<td>Ocry gel 10 g</td>
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			<td>Induction chamber</td>
			<td>custom made</td>
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			<td>30x17x15 cm</td>
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			<td>Inlet flexible pipe</td>
			<td>Gardena, Germany</td>
			<td>1348-20</td>
			<td>4.6-mm diameter, 3m long</td>
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			<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>
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			<td>Isoflurane, liquid for inhalation</td>
			<td>Vertflurane, Virbac, France</td>
			<td>QN01AB06</td>
			<td>1000 mg/mL</td>
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			<td>KD Scientific syringe pump</td>
			<td>KD sientific, Holliston, USA</td>
			<td>Legato 110</td>
			<td></td>
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		<tr>
			<td>LCModel software</td>
			<td>LCModel Inc., Ontario, Canada</td>
			<td>6.2</td>
			<td></td>
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			<td>Medetomidine hydrochloride</td>
			<td>V&#233;toquinol, S.A., France</td>
			<td>QN05CM91</td>
			<td>Domitor, 1 mg/mL</td>
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		<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>
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		<tr>
			<td>NaCl</td>
			<td>Fresenius Kabi, Germany</td>
			<td>B05XA03</td>
			<td>0.9 % 250 mL</td>
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			<td>Outlet flexible pipe</td>
			<td>Gardena, Germany</td>
			<td>1348-20</td>
			<td>4.6-mm diameter, 4m long</td>
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		<tr>
			<td>Paravision software</td>
			<td>Bruker, Ettlingen, Germany</td>
			<td>6.0.1</td>
			<td></td>
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		<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>
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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 ...

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Combined Transcranial Magnetic Stimulation and Electroencephalography of the Dorsolateral Prefrontal Cortex

Transcranial magnetic stimulation (TMS) is a non-invasive method that produces neural excitation in the cortex by means of brief, time-varying magnetic ...

Conducting Hyperscanning Experiments with Functional Near-Infrared Spectroscopy

Concurrent brain recordings of two or more interacting persons, an approach termed hyperscanning, are gaining increasing importance for our understanding ...

Diffusion Tensor Magnetic Resonance Imaging in Chronic Spinal Cord Compression

Chronic spinal cord compression is the most common cause of spinal cord impairment in patients with nontraumatic spinal cord damage. Conventional magnetic ...