Immunochemical characterization of synaptosomal membrane antigens from chicken brain: Histochemical demonstration of changes in distribution during development

Characterization of an antiserum against an axolemma-enriched fraction

An antiserum was raised to rat central nervous system (CNS) axolemma-enriched fractions (AEF), which showed no cross-reactivity with myelin proteins or liver microsomes yet gave an endpoint titer of 1:51 200 to CNS AEF by the enzyme-linked immunosorbent assay (ELISA). Immunochemical staining of electroblotted proteins from rat CNS and peripheral nervous system (PNS) AEFs separated by gel electrophoresis identified a major reactive band at 38.5 kD. CNS AEF also showed major immunoreactivity at 91 kD (+/- 3 kD) and a broad band from 110 kD to 130 kD. By immunoperoxidase staining the antiserum specifically recognized the axolemma of peripheral nerve and synaptic terminals in the CNS. The significance of the specificity is discussed with respect to anti-synaptosome antisera.

Immunohistochemical localization of a phosphoprotein (B-50) isolated from rat brain synaptosomal plasma membranes

The endogenous phosphorylation in vitro of at least 5 protein bands of rat brain synaptosomal membranes (SPM) is inhibited by the behaviorally active peptide ACTH1-24. One of these proteins, the phosphoprotein band B-50, was isolated from rat brain SPM by SDS-slab gel electrophoresis. An antiserum to B-50 was raised in rabbits. The presence of antibodies to B-50 in the antiserum was demonstrated by immunoperoxidase staining of cryostat sections of a polyacrylamide gel containing the antigen. The production of antibodies was monitored by an indirect immunofluorescence technique using cryostat sections of quick-frozen rat cerebellum. Immunofluorescent staining of the molecular and granular layers was observed, whereas the white matter and the perikarya and Purkinje cells of the cerebellum were not stained. With the use of the peroxidase-antiperoxidase (PAP) method, the immunohistochemical localization of the antigen in the molecular and granular layer of the cerebellum was confirmed. Regions rich in neuropil, like the CA1, CA2, CA3, CA4 and dentate gyrus showed an intense immunostaining. Thus, in agreement with the synaptic origin of B-50, the antiserum reacted with tissue components present in brian regions in synaptic contacts.

Immunochemical comparison of synaptic plasma membrane and synaptic vesicle membrane antigens

A synaptic vesicle fraction and a synaptic plasma membrane fraction obtained after subfractionation of synaptosomes from chick forebrain have been used to produce antisera in rabbits. Immunofluorescence histology with the two antisera revealed that they reacted strongly with synaptic terminal regions present in the chick forebrain, cerebellum and spinal cord. In addition, the synaptic plasma membrane antiserum (but not the synaptic vesicle antiserum) reacted with preterminal axons in the cerebellum and spinal cord. Comparison of the two antisera by two-dimensional immunoelectrophoresis, revealed the presence of common antigens in the synaptosomal vesicle and plasma membrane fractions. Incubation of synaptosomes in vitro with the synaptosomal vesicle antiserum and complement produced a dose-dependent inhibition of synaptosome swelling up to a maximum of 55% of that obtained with the synaptosomal plasma membrane antiserum. The results of this test are consistent with the hypothesis that some synaptosomal vesicle antigens may be present also in the synaptosomal plasma membrane and imply that they face the external surface of the synaptosomes. The fate of vesicle membrane components in synaptosomal plasma membranes is not known. The possibility is discussed that they may be recycled locally by a mechanism similar to that proposed by Heuser and Reese (1973) for re-use of synaptic vesicle membranes at the neuromuscular junction.