Retrograde axonal transport of receptor-bound opiate in the vagus and delayed accumulation in the nodose ganglion.

Opiate receptors measured in vivo with [3H]lofentanil in the rat vagus nerve were found to accumulate on both sides of a ligature. The time-course of accumulation was completely different in the proximal and the distal segments; the labelling was maximal 4 h after injection of [3H]lofentanil above the ligature but 16-24 h below the ligature. In unligated rats, a peak of radioactivity appeared in the nodose ganglion 16 h after injection; vagotomy, vinblastine or chronic treatment with capsaicin prevented the appearance of this delayed accumulation in the ganglion. These foregoing experiments suggest that opiate may act in the cell body of sensory neurones after being internalized at the nerve terminals and then transported retrogradely through fast axoplasmic mechanisms.