Localization & Quantification of Monoamines Neurotransmitters for Neuron Metabolism Comprehension Enhancing

MSI

Bioavailability of Neurotransmitters by Mass
Spectrometry Imaging

Neurotransmitters are critical chemical messengers that transmit signals between neurons. Changes in their concentrations are associated with numerous normal neuronal processes, such as sleep and aging, but also several disease states, including Alzheimer’s disease (AD), Parkinson’s disease (PD), depression, drug addiction, and attention deficit hyperactivity disorder. Small molecules neurotransmitters as monoamines (Dopamine, Adrenaline, Noradrenaline, Serotonin) may represent strategic targets for interventions aimed at sustaining normal mood, motor, and cognitive functions.

ImaBiotech developed a multimodal imaging platform to quantify and localize drug and biomarkers at cellular level with label free imaging techniques. These techniques enable the simultaneous detection of multiple endogenous compounds, as neurotransmitters or neuropeptide (See previous application note), and pharmaceutical agents, as drugs. To date, only limited applications are based on the study of neurotransmitters due to their poor detection. Only few developments allowed to visualize endogenous neurotransmitters in brain tissue sections (1,2). We present in this paper the development of new protocols and reagents enable neurotransmitters extraction increase and facilitating their detection to envision pharmacodynamics studies and disease investigations.

Case Study Illustration

Here we describe an approach that includes a method development for  the histological imaging of monoamines neurotransmitters in histological brain tissue sections. We report an example of the simultaneous mapping of several messengers following in situ derivatization in rat brain tissue sections, in a striatum plan (A) and in a hippocampus plan (B) (Nissl staining) (Figure 1). The derivatization reagent then the matrix was deposited after leaving the reaction for a period of incubation. MSI was applied, and the Figure 1 and 2 summarize the obtained results.

Thanks to the staining / molecular distribution overlay, it is possible to visualize the compound distribution in a specific region of interest. The choice of the type of coloration depends on the structures that one wishes to highlight. In this example, Nissl staining was the more appropriate staining for brain substructures visualization.

So, in this section plan, Dopamine is highlighted in the caudate putamen and the arcuate hypothalamic nucleus, according to the literature (3). Noradrenalin is highly localized in the hypothalamus area (4), Serotonin in the thalamus (5), and Adrenaline in the caudate putamen area (6).

Multimaging software have been also optimized to be able to load large high resolution images (up to 100X) and manage all raw data whatever generated by histology – microscopy or mass spectrometry imaging, in order to obtain more complete and accurate information on the histological localization of the molecules of interest.

Finally, a reproducibility test was then performed to evaluate the analytical variability that could be due to the new sample preparation step (derivatization). To do so, six analytical replicates prepared and analyzed on different days. The table below shows an average variability that was comprised between 10 and 32%.

This development allowed visualizing several monoamines neurotransmitters in rodent brain section. It would be interesting to study animal models with neurological disorders, like Alzheimer disease, Parkinson disease, schizophrenia or depression. It is also applied in order to measure and quantify the drug efficacy to restore the neurotransmitter level into the brain.

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