FAST AXONAL-TRANSPORT OF THE VESICULAR ACETYLCHOLINE TRANSPORTER (VACHT) IN CHOLINERGIC NEURONS IN THE RAT SCIATIC-NERVE

The sciatic nerve, as a part of the peripheral nervous system (PNS), h as been used to study axonal transport for decades. It contains motor. sensory as well as autonomic axons. The present study has concentrate d on the axonal transport of the synaptic vesicle acetylcholine transp orter (VAChT), using the ''stop-flow/nerve crush'' method. After block ing fast axonal transport by means of a crush, distinct accumulations of various synaptic vesicle proteins, including VAChT, and peptides de veloped during the first hour after crush-operation and marked increas es were observed up to 8 h post-operative. Semiquantitative analysis, using cytofluorimetric scanning (CFS) of immuno-incubated sections, re vealed a rapid rate of accumulation proximal to the crush, and that th e ratio between distal accumulations (organelles in retrograde transpo rt) and proximal accumulations (organelles in anterograde transport) w as about 40%. Most synaptic vesicle proteins were colocalized in the a xons proximal to the crush. VAChT-immunoreactive axons were also immun oreactive for choline acetyltransferase (ChAT). Autonomic axons with V AChT also contained VIP-LI. The results demonstrate (1) that VAChT, as well as other synaptic vesicle proteins, is transported with fast axo nal transport in motor axons as well as in autonomic post-ganglionic n eurons in this nerve, (2) VAChT colocalized in motor axons with SV2 as well as with synaptophysin, indicating storage in the same axonal par ticle, (3) in the autonomic postganglionic sympathetic cholinergic fib res, VAChT colocalized with VIP, but VIP-LI was present in rather larg e granular structures while VAChT-LI was present mostly as small granu lar elements, (4) in motor as well as in autonomic axons ChAT-LI was p resent in VAChT-positive axons, and (5) the ratio of recycling (retrog radely accumulated) VAChT-IR was about 40%, in contrast to the recycli ng fraction of synaptophysin that was about 70%. (C) 1998 Elsevier Sci ence Ltd. All rights reserved.