At the present, we mainly combine in situ enzyme histochemistry and MALDI imaging mass spectrometry to be able to quickly identify and map the effect of different enzyme inhibitors in brain and spinal cord. We have recently published a proof-of-concept study that demonstrate how different enzymes are localized to specific areas of the brain and contribute to different metabolic profiles. We have introduced two variants of the method; one based on using a simple micropipette to apply reagents and that can be used in any lab with a MALDI-TOF mass spectrometer. The other variant use a chemical ink-jet printer in order to decrease variability and increase precision, so that the metabolites can be localized to various anatomical regions. By using a printer we will be able to increase incubation times without risking peptide delocalization, and thereby we will be able to study the stability of the enzyme inhibitors in situ. Preliminary data show complete block of conversion into certain fragments using pM concentrations, which equals to 10 attomol per matrix deposit demonstrating a very high sensitivity of ISH MALDI imaging MS. This new method can be used for a variety of enzyme systems and models.