A Mouse Holder for Awake Functional Imaging in Unanesthetized Mice: Applications in 31P Spectroscopy, Manganese-Enhanced Magnetic Resonance Imaging Studies, and Resting-State Functional Magnetic Resonance Imaging

Abstract

Anesthesia is often used in preclinical imaging studies that incorporate mouse or rat models. However, multiple reports indicate that anesthesia has significant physiological impacts. Thus, there has been great interest in performing imaging studies in awake, unanesthetized animals to obtain accurate results without the confounding physiological effects of anesthesia. Here, we describe a newly designed mouse holder that is interfaceable with existing MRI systems and enables awake in vivo mouse imaging. This holder significantly reduces head movement of the awake animal compared to previously designed holders and allows for the acquisition of improved anatomical images. In addition to applications in anatomical T2-weighted magnetic resonance imaging (MRI), we also describe applications in acquiring 31P spectra, manganese-enhanced magnetic resonance imaging (MEMRI) transport rates and resting-state functional magnetic resonance imaging (rs-fMRI) in awake animals and describe a successful conditioning paradigm for awake imaging. These data demonstrate significant differences in 31P spectra, MEMRI transport rates, and rs-fMRI connectivity between anesthetized and awake animals, emphasizing the importance of performing functional studies in unanesthetized animals. Furthermore, these studies demonstrate that the mouse holder presented here is easy to construct and use, compatible with standard Bruker systems for mouse imaging, and provides rigorous results in awake mice.

Construction of a Functional Nucleic Acid-Based Artificial Vesicle-Encapsulated Composite Nanoparticle and Its Application in Retinoblastoma-Targeted Theranostics

“…Meanwhile, the release of Mn 2+ was determined by a MR spectrometer due to the paramagnetism of Mn 2+ , thus enabling sensitive tumor imaging by MRI. 53 As shown in Figure 3C,D, a negligible T1 MRI signal of Apt-EG@Dual/ hMNs was observed without GSH. However, after the addition of GSH, the T1 signal of Apt-EG@Dual/hMNs was significantly elevated and showed a high signal shadow in the T1 relaxation MRI mode.…”

“…To verify this hypothesis, Dual/hMNs was incubated in PBS with different concentrations of GSH in the range of cancer cell GSH concentrations (1–10 mM) and showed that the fluorescence intensity gradually recovered with increasing concentration of GSH (Figures B and S4), suggesting that hMNs can be reduced by GSH and consequently release DNAzymes. Meanwhile, the release of Mn 2+ was determined by a MR spectrometer due to the paramagnetism of Mn 2+ , thus enabling sensitive tumor imaging by MRI . As shown in Figure C,D, a negligible T1 MRI signal of Apt-EG@Dual/hMNs was observed without GSH.…”

The eyelid and pupil dynamics underlying stress levels in awake mice

“…However, one significant challenge needs to be carefully considered, i.e., the potential stress caused to the animals during the imaging procedures, which can severely affect physiological states and brain hemodynamic activities. In previous studies, researchers have utilized various methods to measure stress levels in rodents, such as plasma corticosterone levels [2], changes in blood pressure, respiration rate or heat rate [7][8][9], etc. Though those measurements can be applied, it is still crucial to consider the limitations and potential confounding factors of each method when applying to the awake animals, particularly for awake fMRI protocols.…”

In Vivo Biomarker Imaging: Paving the Way for Precision Medicine

“…The advancement of powerful in vivo imaging technology necessitates not only the development of more sensitive and specific imaging agents, but also more accurate detection and analysis methods. In this Special Issue, three reports focus on technical advancements [ 8 , 9 , 10 ]. These technical advances have led to enhanced in vivo imaging platforms that aid in the observation and quantification of intricate physiological and pathological changes.…”

“…These technical advances have led to enhanced in vivo imaging platforms that aid in the observation and quantification of intricate physiological and pathological changes. Notably, the development of a holder that is suited to the functional and molecular imaging of awake mice provides more rigorous results than those obtained from anesthetized mice [ 9 ].…”