October 28, 2024Open Access

Detection of changes in membrane potential by magnetic resonance imaging

Q: What is the clinical evidence from this study?

Study design: Other. Population: Membrane potential changes (n=12). Intervention: Membrane potential depolarization via high K+ concentration vs. Baseline aCSF (3 mM K+). Primary outcome: Change in T2 relaxation time (ΔT2) at 24 minutes (ΔT2 difference 0.918 ms, p=0.00172).

Key Result

Depolarization of the membrane potential using 80 mM K+ significantly increased T2 relaxation time by 1.10 ms compared to 0.181 ms in controls in an in vivo rat model.

Structured PICO

Does manipulation of membrane potential alter magnetic resonance parameters (T2 and PSR) in cultured cells and in vivo rat models?

Population

Cultured human cell lines (SH-SY5Y neuroblastoma and Jurkat leukemia) and in vivo male Wistar rats (8 weeks old, 250-300 g, n=12).

Intervention

Modulation of membrane potential using varying extracellular potassium concentrations ([K+] 0.2-80 mM) or barium ions (10 mM) in vitro, and artificial cerebrospinal fluid with high [K+] (40, 80 mM) in vivo.

Comparator

Control conditions with baseline potassium concentrations ([K+] = 4.2 mM in vitro; [K+] = 3 mM in vivo).

Outcome

Changes in magnetic resonance parameters (T2 relaxation time, pool size ratio [PSR], and magnetization transfer rate [kmf]).surrogate

MRI parameters such as T2 relaxation time and pool size ratio can detect changes in cellular membrane potential, offering a potential noninvasive approach for functional imaging.

Main Result

Effect estimate: ΔT2 difference 0.918 ms

Absolute Event Rate: 1.1% vs 0.181%

p-value: p=0.00172

Limitations

Actual extracellular [K+] experienced by cells in the rat cortex may be lower than that of the perfused aCSF due to diffusion-limiting barriers
Removal of excessive K+ by clearing mechanisms
Partial volume effects and cell type differences
Changes in MR parameters do not measure the membrane potential itself
Other factors such as pH, energy depletion, or extracellular osmolarity may affect MR parameters by altering cell volume
Experimental paradigm was based on clamping the membrane potential at a specific level rather than dynamic changes

Abstract

Abstract Membrane potential plays a crucial role in various cellular functions. However, existing techniques for measuring membrane potential are often invasive or have limited recording depth. In contrast, magnetic resonance imaging (MRI) offers noninvasive imaging with desirable spatial resolution over large areas. This study investigates the feasibility of utilizing MRI to detect membrane potential changes by measuring magnetic resonance parameters while manipulating membrane potential in cultured cells and in vivo rat models. Our findings reveal that depolarization (or hyperpolarization) of the membrane potential increases (or decreases) the T2 relaxation time, while the ratio of bound to free water proton shows the opposite trend. These findings also suggest a pioneering approach to noninvasively detect changes in membrane potential using MRI.

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Cite This Study

Min et al. (Mon,) conducted a other in Membrane potential changes (n=12). Membrane potential depolarization via high K+ concentration vs. Baseline aCSF (3 mM K+) was evaluated on Change in T2 relaxation time (ΔT2) at 24 minutes (ΔT2 difference 0.918 ms, p=0.00172). Depolarization of the membrane potential using 80 mM K+ significantly increased T2 relaxation time by 1.10 ms compared to 0.181 ms in controls in an in vivo rat model.

synapsesocial.com/papers/6a0dd15fcae7912d2fa553ab https://doi.org/https://doi.org/10.7554/elife.101642.1

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