Correlation between choline signal intensity and acetylcholine level in different brain regions of rat

Acetylcholine is an important excitatory neurotransmitter, which plays a crucial role in synaptic transmission. The level of acetylcholine is decreased in the early stages of Alzheimer disease (AD), the most common neurodegenerative disease. Therefore, measurement of acetylcholine in the brain may help the clinical diagnosis of AD. However, the methods used till now to detect the brain acetylcholine level are invasive, which are neither recommended nor acceptable in the clinic. Acetylcholine is synthesized from choline-containing compounds (Cho), the latter can be estimated by noninvasive proton magnetic resonance spectroscopy ((1)H MRS). To explore whether the Cho signal intensity could be used to represent the acetylcholine level in the brain, we employed (1)H MRS to detect the Cho signal, and simultaneously, we also used microdialysis and high-performance liquid chromatography (HPLC) to measure the level of acetylcholine in hippocampus, striatum, frontal cortex, and somatosensory barrel field (S1BF cortex) of rats, respectively. The results showed that the correlations between Cho signal intensity and acetylcholine level in hippocampus, striatum, frontal cortex, and S1BF cortex were, respectively, 0.823 (p = 0.044), 0.851 (p = 0.032), 0.817 (p = 0.047), and 0.822 (p = 0.045). The F-values of the regression model were, respectively, 8.404 (p = 0.044), 10.47 (p = 0.032), 8.000 (p = 0.047), and 8.326 (p = 0.045). And the derived regression equations were y = 0.67x + 1.363 (hippocampus), y = 5.398x + 6.684 (striatum), y = 0.656x + 0.564 (frontal cortex), and y = 0.394x + 1.127 (S1BF cortex), respectively (y means acetylcholine, and x means Cho). These data suggest that the Cho signal intensity observed by (1)H MRS may be used as an indicator of acetylcholine level in different brain regions of the rats.