Chemical exchange saturation transfer (CEST) MRI was performed for the evaluation of cerebral metabolic changes in a rat model of depressive-like disease induced by chronic unpredictable mild stress (CUMS). CEST Z-spectra were acquired on a 7 T MRI with two saturation B₁ amplitudes (0.5 and 0.75 µT) to measure the magnetization transfer ratio (MTR), CEST and relayed nuclear Overhauser effect (rNOE). Cerebral cortex and hippocampus were examined in two groups of animals: healthy control (n = 10) and stressed (n = 14), the latter of which was exposed to eight weeks of the CUMS protocol. The stressed group Z-spectrum parameters, primarily MTRs, were significantly lower than in controls, at all selected frequency offsets (3.5, 3.0, 2.0, − 3.2, − 3.6 ppm) in the cortex (the largest difference of ~ 3.5% at − 3.6 ppm, p = 0.0005) and the hippocampus (MTRs measured with a B₁ = 0.5 µT). The hippocampal rNOE contributions decreased significantly in the stressed brains. Glutamate concentration (assessed using ELISA) and MTR at 3 ppm correlated positively in both brain regions. GABA concentration also correlated positively with CEST contributions in both cerebral areas, while such correlation with MTR was positive in hippocampus, and nonsignificant in cortex. Results indicate that CEST is sensitive to neurometabolic changes following chronic stress exposure.

化学交换饱和转移 (CEST) MRI 用于评估慢性不可预知轻度应激 (CUMS) 诱导的抑郁样疾病大鼠模型的脑代谢变化。CEST Z 谱是在具有两个饱和度 B _{1的 7 T MRI 上采集的}振幅（0.5 和 0.75 µT）以测量磁化传递比 (MTR)、CEST 和中继核 Overhauser 效应 (rNOE)。在两组动物中检查了大脑皮层和海马体：健康对照组 (n = 10) 和压力组 (n = 14)，后者暴露于 CUMS 方案的八周。在皮层中所有选定的频率偏移（3.5、3.0、2.0、- 3.2、- 3.6 ppm），压力组 Z 谱参数（主要是 MTR）明显低于对照组（最大差异为 ~ 3.5%，在 - 3.6 ppm，p = 0.0005）和海马体（用 B _{1测量的 MTR} = 0.5 µT)。海马 rNOE 贡献在受压大脑中显着下降。谷氨酸浓度（使用 ELISA 评估）和 3 ppm 的 MTR 在两个大脑区域呈正相关。GABA 浓度也与两个大脑区域的 CEST 贡献呈正相关，而这种与 MTR 的相关性在海马体中呈正相关，而在皮质中则不显着。结果表明 CEST 对慢性应激暴露后的神经代谢变化敏感。