DIFFERENCES IN THE DISTRIBUTION OF CYTOCHROME B(561) AND SYNAPTOPHYSIN IN DOG SPLENIC NERVE - A BIOCHEMICAL AND IMMUNOCYTOCHEMICAL STUDY

Compared with neurons of the CNS, the organization of the peripheral a drenergic axon and nerve terminal is more complex because two types of neurotransmitter-containing vesicles, i.e., large (LDVs) and small de nse-core vesicles, coexist with the axonal reticulum (AR) and the well -characterized small synaptic vesicles. The AR, which is still poorly examined, is assumed to play some role in neurosecretion. We have stud ied the subcellular localization of noradrenaline, cytochrome b(561), and synaptophysin in control and ligated dog splenic nerve using both biochemical and ultrastructural approaches. Noradrenaline and cytochro me b(561) coaccumulated proximal to a ligation, whereas distally only the latter was found. Despite a codistribution with noradrenaline at h igh densities in sucrose gradients, synaptophysin did not accumulate o n either side of the ligation. At the ultrastructural level, cytochrom e b(561) immunoreactivity was found on LDVs and AR elements, both accu mulating proximal to the ligation. Distally, the multivesicular bodies (MVBs), immunolabeled for cytochrome b(561), account for the retrogra de transport of LDVs and AR membranes retrieved at the nerve terminal. No synaptophysin immunoreactivity could be detected on LDVs, AR, or M VBs. The results obtained from the ligation experiments together with the ultrastructural data clearly illustrate that synaptophysin is abse nt from LDVs and AR elements in adrenergic axons.