DISTRIBUTION OF RAB3A IN RAT NERVOUS-SYSTEM - COMPARISON WITH OTHER SYNAPTIC VESICLE PROTEINS AND NEUROPEPTIDES

In the present study we have investigated the distribution of Rab3a in rat peripheral nervous system and compared it with the distribution o f other synaptic vesicle proteins (synaptophysin, synapsin I), neurope ptides (CGRP, SP, NPY) and tyrosine hydroxylase (TH). Rab3a immunoreac tivity (-IR) was always colocalized with synaptophysin-IR and synapsin I-IR in nerve terminals of the spinal cord and peripheral nerve endin gs. In many cases, Rab3a-IR was also present in the same axons and ter minals as peptides. In crushed sciatic nerve axons, Rab3a was colocali zed, proximal to the crush, with synaptophysin-IR, synapsin I-IR, CGRP -IR, and TH-IR, but only partially co-localized with NPY-IR and SP-IR. In the area distal to the crush, Rab3a-IR was very weakly positive in a few thin axons, while larger amount of synaptophysin, CGRP, NPY and SP immunoreactivities were detected. The subcellular distribution of peptides and Rab3a differed in that peptides were observed mainly in l arge granular structures, while Rab3a-IR was observed mainly as diffus e, finely granular immunoreactivity, in addition to a few exceptional large granules present in some axons. The results demonstrate that Rab 3a is widely distributed in different types of neurons, i.e. motor, se nsory, autonomic adrenergic and cholinergic neurons, and colocalized w ith other synaptic vesicle proteins, suggesting that Rab3a may play an essential role in neuronal function. Furthermore, Rab3a is present in many peptide containing axons and terminals, but with an apparently d ifferent subcellular distribution, being affiliated mostly with small synaptic vesicles and only occasionally with large vesicles, that may represent peptide contained vesicles.