One-pot synthesis of carboxymethyl-dextran coated iron oxide nanoparticles (CION) for preclinical fMRI and MRA applications

Das, Manasmita; Oyarzabal, Esteban A.; Chen, Lars; Lee, Sungho; Shah, Neal; Gerlach, Gabby; Zhang, Weiting; Chao, Tzu-Hao Harry; Berge, Nathalie Van Den; Liu, Carolyn; Donley, Carrie L.; Montgomery, Stephanie A.; Shih, Yu Jen

doi:10.1016/j.neuroimage.2021.118213

Cited by 21 publications

(20 citation statements)

References 138 publications

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“…Subjects were continuously recorded for 40 min with a dose of CNO (1 mg/kg) administered via an intraperitoneal catheter 10 min after scan onset. CBV-weighted fMRI was achieved by a bolus dose of an in-house–developed iron oxide nanoparticle (30 mg of Fe/kg, intravenously) ( 87 ). Rectal body temperatures were continuously maintained at 37° ± 0.5°C with a temperature controller (Oakton Temp9500, Cole-Parmer, Vernon Hills, IL, USA) coupled to a circulating water bath (Haake S13, Thermo Fisher Scientific, Waltham, MA, USA) that heats the MRI mouse cradle.…”

Section: Methodsmentioning

confidence: 99%

Chemogenetic stimulation of tonic locus coeruleus activity strengthens the default mode network

et al. 2022

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The default mode network (DMN) of the brain is functionally associated with a wide range of behaviors. In this study, we used functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and spectral fiber photometry to investigate the selective neuromodulatory effect of norepinephrine (NE)–releasing noradrenergic neurons in the locus coeruleus (LC) on the mouse DMN. Chemogenetic-induced tonic LC activity decreased cerebral blood volume (CBV) and glucose uptake and increased synchronous low-frequency fMRI activity within the frontal cortices of the DMN. Fiber photometry results corroborated these findings, showing that LC-NE activation induced NE release, enhanced calcium-weighted neuronal spiking, and reduced CBV in the anterior cingulate cortex. These data suggest that LC-NE alters conventional coupling between neuronal activity and CBV in the frontal DMN. We also demonstrated that chemogenetic activation of LC-NE neurons strengthened functional connectivity within the frontal DMN, and this effect was causally mediated by reduced modulatory inputs from retrosplenial and hippocampal regions to the association cortices of the DMN.

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Section: Methodsmentioning

confidence: 99%

Chemogenetic stimulation of tonic locus coeruleus activity strengthens the default mode network

et al. 2022

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“…A month after the virus microinjection, the skin was reopened to expose the skull, then the bone wax was removed and optical fibers (200 μm in diameter; NA: 0.39) were chronically implanted to coordinates 0.3 mm above the virus injection sites. We did not identify any significant size change in adult rat brains during the 1-month virus incubation before fiber implantation according to our recent study, 49 thus no re-adjustment of the coordinates for fiber implantation was applied. Four MR-compatible miniature brass screws (Item #94070A031, McMaster Carr, Atlanta, Georgia) were anchored to the skull, then the surface of the skull was covered with dental cement to seal implanted components and the wound was sutured to further protect the surgical site.…”

Section: Stereotactic Surgerymentioning

confidence: 99%

“…To untangle the GCaMP and Rhodamine spectra, mixed spectra acquired by fiber-photometry were analyzed using a spectral linear unmixing algorithm, which can effectively remove crosstalk between multicolor sensors as shown in previous studies. 42,43,49 Briefly, at any time point n, the mixed spectrum YðnÞ was modeled as E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 0 4 ; 1 1 6 ; 6 6 8…”

Section: Fiber-photometry Spectral Unmixingmentioning

confidence: 99%

Computing hemodynamic response functions from concurrent spectral fiber-photometry and fMRI data

et al. 2022

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Significance: Although emerging evidence suggests that the hemodynamic response function (HRF) can vary by brain region and species, a single, canonical, human-based HRF is widely used in animal studies. Therefore, the development of flexible, accessible, brain-region specific HRF calculation approaches is paramount as hemodynamic animal studies become increasingly popular.Aim: To establish an fMRI-compatible, spectral, fiber-photometry platform for HRF calculation and validation in any rat brain region.Approach: We used our platform to simultaneously measure (a) neuronal activity via genetically encoded calcium indicators (GCaMP6f), (b) local cerebral blood volume (CBV) from intravenous Rhodamine B dye, and (c) whole brain CBV via fMRI with the Feraheme contrast agent. Empirical HRFs were calculated with GCaMP6f and Rhodamine B recordings from rat brain regions during resting-state and task-based paradigms.Results: We calculated empirical HRFs for the rat primary somatosensory, anterior cingulate, prelimbic, retrosplenial, and anterior insular cortical areas. Each HRF was faster and narrower than the canonical HRF and no significant difference was observed between these cortical regions. When used in general linear model analyses of corresponding fMRI data, the empirical HRFs showed better detection performance than the canonical HRF.Conclusions: Our findings demonstrate the viability and utility of fiber-photometry-based HRF calculations. This platform is readily scalable to multiple simultaneous recording sites, and adaptable to study transfer functions between stimulation events, neuronal activity, neurotransmitter release, and hemodynamic responses.

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“…Next, rats were secured in a custom MRI cradle and a fiber optic patch cable (200 µm core, .22 NA, 7 m long), set to deliver blue light from a solid-state laser, was connected to the implanted fiber in each rat for optogenetic stimulation of the AI. Subsequently, rats were positioned in the MRI bore, anatomical scans were completed, then a functional scan was acquired during which the CBV contrast agent Feraheme (30 mg/kg intravenous) was administered to augment detection sensitivity and measure CBV-weighted signal changes (41,(79)(80)(81). Finally, rats were switched to a well-established sedation protocol combining low dose (0.5%) isoflurane with a cocktail of intravenous dexmedetomidine (0.05 mg/kg/hr) and pancuronium (0.5 mg/kg/hr), and allowed 30 minutes for their physiological parameters to stabilize before optogenetic-fMRI scanning.…”

Section: Preparation Of Rats For Fmri Scanningmentioning

confidence: 99%

Optogenetic stimulation of anterior insular cortex neurons reveals causal mechanisms underlying suppression of the default mode network by the salience network

Menon

Cerri

Lee³

et al. 2022

Preprint

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The salience network (SN) and default mode network (DMN) are among the most widely investigated networks in the human brain. The SN, anchored in the anterior insular cortex (AI), is thought to play a critical role in stimulus-driven suppression of DMN nodes. However, the causal neural mechanisms underlying DMN suppression and SN-DMN interactions are poorly understood. Here we combine feedforward optogenetic AI stimulation with fMRI and computational modeling to dissect the causal role of AI in dynamic functional interactions between SN and DMN nodes in the rat brain. Optogenetic stimulation of Chronos-expressing AI neurons in rats suppressed DMN activity and decreased AI-DMN and intra-DMN functional connectivity. Our findings demonstrate that feedforward optogenetic stimulation of AI neurons induces dynamic suppression and decoupling of the DMN and elucidates previously unknown features of rodent brain network organization. Our study advances foundational knowledge of causal mechanisms underlying dynamic cross-network interactions and brain network switching.

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One-pot synthesis of carboxymethyl-dextran coated iron oxide nanoparticles (CION) for preclinical fMRI and MRA applications

Cited by 21 publications

References 138 publications

Chemogenetic stimulation of tonic locus coeruleus activity strengthens the default mode network

Chemogenetic stimulation of tonic locus coeruleus activity strengthens the default mode network

Computing hemodynamic response functions from concurrent spectral fiber-photometry and fMRI data

Optogenetic stimulation of anterior insular cortex neurons reveals causal mechanisms underlying suppression of the default mode network by the salience network

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