Endogenous fluorescence induced by multiphoton microscopy on rehydrated cryosections of mouse brain.

A: Multiphoton image of cortical tissue after 240 scans in the area indicated by the box and TPEF images showing the irradiated area at scan n. 1, 94, 168 and 240; the arrow indicates the very first increase of TPEF at scan 110. B: Cerebellar tissue after 224 scans in the area indicated by the box and TPEF images showing the irradiated area at scan n. 1, 108, 162 and 224; the arrow indicates the very first increase of TPEF at scan n. 108. In both cases H&E staining of a consecutive section is provided as reference for tissue structures. C: Magnified image of the region indicated by the dashed box in B: TPEF (green) and CARS (red) are shown separately and merged. Arrows indicate spots of strong TPEF that colocalize with decreased CARS signal intensity. All experiments were performed with a total laser power of ∼52 mW in the sample.