Biocytin hydrazide an be used as microinjectable anterograde and transneuronal tracers that is fixable with aldehyde-based fixatives. Additionally, the primary aliphatic amine of this molecule can be reversibly coupled to aldehydes and ketones to form a Schiff base - which can be reduced to a stable amine derivative by sodium borohydride (NaBH₄) or sodium cyanoborohydride (NaCNH₃) to form new biotinylated probes. Carboxylic acids of proteins and other water-soluble biopolymers can be coupled to this molecule in aqueous solution using water-soluble carbodiimides such as EDAC (E2247).