Long-term retention of Fast Blue in sympathetic neurones after axotomy and regeneration--demonstration of incorrect reconnections.

Using the fluorescent dyes Fast Blue and Diamidino Yellow to trace neuronal connections, the regeneration of the superior cervical ganglionic neurones after axotomy has been examined. Fast Blue has the property of remaining within the neuronal perikaryon for many months after its retrograde axonal transport, even after transection of the axon. Thus, Fast Blue can be used to label neurones as to their original target and Diamidino Yellow subsequently used to demonstrate the specificity of reconnection. The results suggest that apparent return of appropriate function occurs in the presence of a large component of inappropriate reconnections.