Identification of spinothalamic tract cells in fresh, unfixed rat spinal cord

Diamidino yellow dihydrochloride (DY . 2HCl) can reliably label spinothalamic tract cells both in the perfused, fixed and in the fresh, unfixed rat spinal cord. The major advantages of DY . 2HCl as a retrograde marker are that it leaks from the cells very slowly and can be conveniently identified in unfixed neurons by fluorescence microscopy. DY . 2HCl will be a useful marker for identification of spinothalamic tract cells that are to be studied in vitro.