Axonal transport of neuropeptides: Retrograde tracing study in live cell cultures of rat sympathetic cervical ganglia

Abstract

Previous studies demonstrated that neuropeptides are transported with fast axonal transport. Considerable amounts (30-40%) of anterogradely transported peptides accumulated distal to a crush, apparently recycling to the cell bodies. In the present study, we used primary and compartmented cultures of sympathetic cervical ganglia (SCG) to address questions on the origin of the recycling peptides. In primary cultures, distinct labeling of neuropeptide Y (NPY) or secretoneurin (SN) immunoreactivities was detected in varicosities and in cell bodies, after administration of NPY or SN antibodies to the living cultures. Simultaneous addition to the medium with antibody against the N-terminal (lumen) domain of synaptotagmin, resulted in a partial overlapping between synaptotagmin and NPY/SN. In compartmented chamber cultures, in which cell body and proximal segments of the processes are restricted to the central chamber and the distal processes are present in peripheral compartments, antibody administration was performed in the peripheral compartment. KCl (60-120 mM) was added to the central chamber for 10 sec, followed by washing, and 30-60 min later clear labeling was detected in the cell bodies, suggesting that the antibodies were now present in structures that were transported from the distal segments in the peripheral compartment to the cell body. The results indicate 1) that peptide release from large dense cored vesicles is incomplete; 2) that the remaining peptides, together with the membrane, are retrogradely transported to cell bodies; and 3) that the recycling peptides accumulating distal to a crush of a peripheral nerve are most likely to be recycled from the nerve terminals.