Pyrylium based derivatization imaging mass spectrometer revealed the localization of L-DOPA

PLoS One. 2022 Aug 2;17(8):e0271697. doi: 10.1371/journal.pone.0271697. eCollection 2022.


Simultaneous imaging of l-dihydroxyphenylalanine (l-DOPA), dopamine (DA) and norepinephrine (NE) in the catecholamine metabolic pathway is particularly useful because l-DOPA is a neurophysiologically important metabolic intermediate. In this study, we found that 2,4,6-trimethylpyrillium tetrafluoroborate (TMPy) can selectively and efficiently react with target catecholamine molecules. Specifically, simultaneous visualization of DA and NE as metabolites of l-DOPA with high steric hinderance was achieved by derivatized-imaging mass spectrometry (IMS). Interestingly, l-DOPA showed strong localization in the brainstem, in contrast to the pattern of DA and NE, which co-localized with tyrosine hydroxylase (TH). In addition, to identify whether the detected molecules were endogenous or exogenous l-DOPA, mice were injected with l-DOPA deuterated in three positions (D3-l-DOPA), which was identifiable by a mass shift of 3Da. TMPy-labeled l-DOPA, DA and NE were detected at m/z 302.1, 258.1 and 274.1, while their D3 versions were detected at 305.0, 261.1 and 277.1 in mouse brain, respectively. l-DOPA and D3-l-DOPA were localized in the BS. DA and NE, and D3-DA and D3-NE, all of which are metabolites of L-DOPA and D3-l-DOPA, were localized in the striatum (STR) and locus coeruleus (LC). These findings suggest a mechanism in the brainstem that allows l-DOPA to accumulate without being metabolized to monoamines downstream of the metabolic pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Catecholamines
  • Dopamine* / metabolism
  • Levodopa*
  • Mass Spectrometry
  • Mice
  • Norepinephrine / metabolism


  • Catecholamines
  • Levodopa
  • Dopamine
  • Norepinephrine

Grants and funding

This research was funded by Japan Science and Technology (JST) Grants-in-A-STEP (VP30118067678 to S.T.), Grant-in-Aid for Scientific Research B (21H02133 to S.T.) and the LOTTE Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.