Fast Blue and Diamidino Yellow as retrograde tracers in peripheral nerves:efficacy of combined nerve injection and capsule application to transectednerves in the adult rat

Capsule application of Diamidino Yellow (DY) to the cut end of the sciatic nerve immediately followed by capsule application of Fast Blue (FB) resulte d in approximate to 95% double-labelled dorsal root ganglion neurones (DRGn ) and motoneurones (Mn). Nerve injection of DY followed either immediately or 2 months later by capsule application of FB resulted in approximate to 9 0% double-labelled DRGn and Mn, indicating that DY and FB label similar pop ulations of DRGn and Mn, and that insignificant DY fading occurred during t his period. Inversing the order of application, however, i.e. nerve injecti on of FB followed immediately by capsule application of DY, resulted in dou ble labelling in only approximate to 10% of the DRGn and Mn. These percenta ges increased to 70% of the DRGn and 60% of the Mn when the FB injection wa s followed 1 or 2 months after by the DY application, indicating that DY up take is blocked by recent administration of FB. The results indicate that D Y and FB might be useful for sequential labelling before and after nerve in jury as a tool to investigate the accuracy of sensory and motor regeneratio n. (C) 2000 Elsevier Science B.V. All rights reserved.