Funktionel Neuroimaging Med Ultrasonic blod-hjerne barrieren forstyrrelser og mangan-forstærket MRI
Summary
En teknik er beskrevet for bredt åbning af blod-hjerne-barrieren hos mus ved hjælp af mikrobobler og ultralyd. Anvendelse af denne teknik, kan mangan indgives til musehjerne. Fordi mangan er en MRI-kontrastmiddel, der ophobes i depolariserede neuroner, denne tilgang gør det muligt billeder af neuronal aktivitet.
Abstract
Selv mus er den dominerende model for at studere de genetiske og molekylære fundament for neurovidenskab, funktionel Neuroimaging i mus er stadig teknisk udfordrende. Én fremgangsmåde, aktiverings-induceret mangan-MRI (AIM MRI) er blevet anvendt med succes til at kortlægge neuronal aktivitet i gnavere 1-5. I AIM MRI, + Mn 2 virker som en calcium analog og akkumuleres i depolariserede neuroner 6,7. Fordi Mn 2 + forkorter T 1 vævet ejendom, vil regionerne i forhøjet neuronal aktivitet styrke i MRI. Endvidere Mn2 + fjerner langsomt fra aktiverede regioner, og derfor kan stimulation udføres uden magneten før billeddannelse, hvilket muliggør større eksperimentel fleksibilitet. Men fordi Mn2 +, ikke let krydser blod-hjerne-barrieren (BBB), behovet for at åbne BBB har begrænset anvendelsen af AIM MRI, især i mus.
Et redskab til at åbne BBB er ULTrasound. Selvom potentielt skadelig, hvis ultralyd administreres i kombination med gasfyldte mikrobobler (dvs. ultralydskontrastmidler), den akustiske tryk, der kræves for BBB åbning er betydeligt lavere. Denne kombination af ultralyd og mikrobobler kan anvendes til pålideligt at åbne BBB uden at forårsage vævsbeskadigelse 8-11.
Her, er en fremgangsmåde præsenteres til udførelse AIM MRI ved hjælp mikrobobler og ultralyd til at åbne BBB. Efter en intravenøs injektion af perflutren mikrobobler er en ufokuseret pulserende ultralydsstrålen påføres barberede muse hovedet i 3 minutter. For nemheds skyld henviser vi til denne teknik på BBB Åbning med Mikrobobler og ultralyd som BOMUS 12. Anvendelse BOMUS at åbne BBB hele begge cerebrale hemisfærer, er mangan administreres til hele musehjerne. Efter eksperimentel stimulering af let sederede mus, AIM MRI anvendt til at kortlægge den neuronale respons.
Tildemonstrere denne fremgangsmåde, er heri BOMUS og AIM MRI anvendt til at kortlægge ensidig mekanisk stimulering af vibrissae i let sederede mus 13. Fordi BOMUS kan åbne BBB hele begge halvkugler, er den ustimulerede side af hjernen, der anvendes til at kontrollere for ikke-specifik baggrund stimulering. Den resulterende 3D aktiveringskort stemmer godt overens med offentliggjorte repræsentationer vibrissae regioner cylinderen felt cortex 14. Ultralyd åbning BBB er hurtig, ikke-invasiv, og reversibel, og derfor er denne fremgangsmåde egnet til high-throughput og / eller langsgående undersøgelser i vågne mus.
Protocol
Discussion
Her blev en metode præsenteret for invasiv åbne BBB hele musen hjernen med ultralyd og mikrobobler (BOMUS). Med BBB åben + Mn 2 blev administreret, og aktiverings-induceret mangan-MRI (AIM MRI) blev anvendt til at afbilde neuronal respons på kortvarig stimulering let sederede mus.
Passende BBB åbning blev opnået med en spids-negativ akustisk tryk på 0,36 MPa. Bemærk, er trykket ved hovedbunden overflade ved midten af ultralydsstrålen. Målinger af en enke…
Disclosures
The authors have nothing to disclose.
Acknowledgements
Alt arbejde blev udført på Duke Center for In Vivo Microscopy, en NIH / NIBIB National Biomedical Technology Resource Center (P41 EB015897) og NCI Mindre Husdyrs Imaging Resource Program (U24 CA092656). Yderligere støtte blev givet fra NSF Graduate Research Fellowship (2003014921).
Materials
| Name of the reagent | Company | Catalog number | Comments |
| Hydrophone | Sonora Medical Systems, Longmont, CA | SN S4-251 | |
| Translation stage | Newport Corporation, Irvine, CA | ||
| Ultrasound transducer | Olympus NDT, Inc., Waltham MA | A306S-SU | Review the manufacturer’s test sheet that accompanies the transducer to find the exact center frequency of that particular transducer, which may differ from the nominal frequency listed in the catalog. (e.g., the nominal frequency of our transducer was 2.25 MHz, but the actual center frequency was 2.15 MHz.) |
| Vevo Imaging Station | VisualSonics, Inc. Toronto, Canada | ||
| 50 dB power amplifier | E&I, Rochester, NY | model 240L | |
| Signal generator | Agilent Technologies, Santa Clara, CA | model 33220A | |
| MnCl2-(H2O)4 | Sigma | Molecular weight varies by batch, call manufacturer for exact measurement | |
| Perflutren lipid microspheres | Lantheus Medical Imaging, N. Billerica, MA | DEFINITY | |
| Microsphere agitator | Lantheus Medical Imaging, N. Billerica, MA | VIALMIX | |
| MR imaging coil | m2m Imaging Corp., Hillcrest, OH | 35 mm diameter quadrature transmit/receive volume coil | |
| MRI system | GE Healthcare, Milwaukee, WI | GE EXCITE console operating a 7-T horizontal bore magnet | |
| Image analysis environment | Visage Imaging, San Diego, CA, MathWorks, Natick MA | Amira MATLAB |
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