ULTRASTRUCTURAL-LOCALIZATION OF NEUROPEPTIDE Y-IMMUNOREACTIVITY IN THE AXONAL RETICULUM ELEMENTS, ACCUMULATING ANTEROGRADELY IN TRANSECTED RAT SCIATIC-NERVE

The detection of dopamine-beta-hydroxylase and cytochrome B561 on the membranes of the axonal reticulum demonstrated that in sympathetic neu rons the different compartments of the axonal reticulum participate in the formation of neurosecretory vesicles. In the present study we tri ed to reveal that the components of the vesicular content are also cha nneled along the axonal reticulum, by examining whether neuropeptide Y could be localized in elements of the axonal reticulum. Therefore 6 h transected rat sciatic nerve was embedded in glycolmethacrylate and a n immunogold labeling was performed. Counterstaining with phosphotungs tic acid at low pH selectively contrasted the accumulated axonal retic ulum elements and associated granules. In the non-myelinated axons gol d labeling was localized on granules and on tubular and granular profi les, demonstrating the presence of neuropeptide Y in the accumulated a xonal reticulum elements. This indicates that neuropeptides are indeed transported via the axonal reticulum to the nerve ending and suggests that the accumulation of large dense-cored vesicles at a block is mai nly due to local new formation rather than down transport.