Fig. 5 The ion map for m/z 772, m/z 734 and m/z 744 obtained from the slices of the spinal cord for norharmane matrix with the different number of matrix layers (A) and four different heights of spraying nozzle (B) for the positive ionization mode (matrix: 6 mg/ml norharmane (chloroform:MeOH:H2O))