title: Expression of exocytosis proteins in rat supraoptic nucleus neurones.
abstract: In magnocellular neurones of the supraoptic nucleus (SON), the neuropeptides vasopressin and oxytocin are synthesised and packaged into large dense-cored vesicles (LDCVs). These vesicles undergo regulated exocytosis from nerve terminals in the posterior pituitary gland and from somata/dendrites in the SON. Regulated exocytosis of LDCVs is considered to involve the soluble N-ethylmaleimide sensitive fusion protein attachment protein receptor (SNARE) complex [comprising vesicle associated membrane protein 2 (VAMP-2), syntaxin-1 and soluble N-ethylmaleimide attachment protein-25 (SNAP-25)] and regulatory proteins [such as synaptotagmin-1, munc-18 and Ca(2+) -dependent activator protein for secretion (CAPS-1)]. Using fluorescent immunocytochemistry and confocal microscopy, in both oxytocin and vasopressin neurones, we observed VAMP-2, SNAP-25 and syntaxin-1-immunoreactivity in axon terminals. The somata and dendrites contained syntaxin-1 and other regulatory exocytosis proteins, including munc-18 and CAPS-1. However, the distribution of VAMP-2 and synaptotagmin-1 in the SON was limited to putative pre-synaptic contacts because they co-localised with synaptophysin (synaptic vesicle marker) and had no co-localisation with either oxytocin or vasopressin. SNAP-25 immunoreactivity in the SON was limited to glial cell processes and was not detected in oxytocin or vasopressin somata/dendrites. The present results indicate differences in the expression and localisation of exocytosis proteins between the axon terminals and somata/dendritic compartment. The absence of VAMP-2 and SNAP-25 immunoreactivity from the somata/dendrites suggests that there might be different SNARE protein isoforms expressed in these compartments. Alternatively, exocytosis of LDCVs from somata/dendrites may use a different mechanism from that described by the SNARE complex theory.
authors: Centre for Integrative Physiology, University of Edinburgh, Edinburgh, UK.
authors: V
authors: V
authors: Tobin
authors: Y
authors: Y
authors: Schwab
authors: N
authors: N
authors: Lelos
authors: T
authors: T
authors: Onaka
authors: Q J
authors: QJ
authors: Pittman
authors: M
authors: M
authors: Ludwig
mesh_terms: D000818:Animals; D005089:Exocytosis / Q000502:physiology*; D005260:Female; D015870:Gene Expression / Q000502:physiology; D007150:Immunohistochemistry / Q000379:methods; D066298:In Vitro Techniques; D009457:Neuroglia / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D010121:Oxytocin / Q000502:physiology; D010904:Pituitary Gland, Posterior / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D050600:SNARE Proteins / Q000378:metabolism*; D022142:Secretory Vesicles / Q000378:metabolism; D013495:Supraoptic Nucleus / Q000166:cytology / Q000378:metabolism*; D014667:Vasopressins / Q000502:physiology
chemical_list: D050600:SNARE Proteins; D014667:Vasopressins; D010121:Oxytocin