Spatial pharmacometabolomic profiling of two antipsychotics reveals region-specific neurochemical alterations in the rat brain.

Defining how antipsychotic drugs acutely reshape neurochemical signaling across discrete brain regions is critical for understanding their central pharmacological actions. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) enables spatially resolved, untargeted molecular profiling directly in tissue and is well suited to investigate early drug-induced effects. Here, we applied MALDI-MSI to characterize acute neurochemical and metabolomic alterations and to explore trypsin-digested peptidomic changes in rat brain following single-dose exposure to the atypical antipsychotics risperidone and olanzapine. By using MALDI matrices optimized for neurotransmitters, small metabolites, and peptides, we achieved broad molecular coverage across cortical, striatal, and hippocampal regions. This approach revealed distinct, drug-specific spatial signatures encompassing monoamine-related metabolites, purine metabolism, and lipids. In the striatum, both compounds altered dopamine metabolism, as reflected by changes in 3-methoxytyramine, 3,4-dihydroxyphenylacetic acid, and homovanillic acid. In cortical and hippocampal regions, risperidone selectively increased levels of the norepinephrine metabolite 3-methoxy-4-hydroxyphenylethyleneglycol sulfate, indicating a distinct noradrenergic signature. Pathway analysis identified purine metabolism as a major treatment-responsive pathway, consistent with altered nucleotide homeostasis and energy metabolism. Together, these findings provide spatially resolved insight into how atypical antipsychotics modulate brain chemistry, revealing region-specific neurochemical signatures underlying their pharmacological effects.