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Smooth muscle‐associated protein 8: Distribution and biological activity in the rat brain
Author(s) -
Brailoiu G. Cristina,
Dun Siok L.,
Mizuo Keisuke,
Brailoiu Eugen,
Yang Jun,
Chang Jaw Kang,
Dun Nae J.
Publication year - 2007
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.21315
Subject(s) - supraoptic nucleus , hypothalamus , population , medicine , endocrinology , oxytocin , vasopressin , immunocytochemistry , biology , median eminence , neurophysins , western blot , extracellular , chemistry , microbiology and biotechnology , biochemistry , environmental health , gene
With the use of an antiserum directed against the human smooth muscle‐associated protein 8 (SMAP8) fragment SMAP8 98–138 , Western blot and immunohistochemical studies revealed SMAP8 expression in the rat brain. A band with a molecular size of about 45 kDa was detected in tissues from the rat hypothalamus and a weaker band from the cortex. SMAP8 immunoreactivity (irSMAP8) was detected in neurons of the hypothalamic paraventricular, supraoptic, and supraoptic retrochiasmatic nuclei; a few irSMAP8 cells were scattered in the zona incerta as well as the cerebral cortex. Immunoreactive cell processes were detected mostly in the internal layer of the median eminence. Double labeling the hypothalamic sections with SMAP8 and vasopressin (VP) or oxytocin (OT) antiserum revealed that a population of VP‐ and OT‐immunoreactive neurons expressed irSMAP8. The biological activity of SMAP8 in rat central neurons was assessed by the calcium microfluorimetric Fura‐2 method. SMAP8 (100 nM) elevated cytosolic calcium concentrations [Ca 2+ ] i in a population of dissociated and cultured rat hypothalamic neurons; the response was eliminated in Ca 2+ ‐free saline. This is the first evidence of irSMAP8 in a population of VP/OT‐containing hypothalamic neurons in the rat, and the peptide is biologically active in hypothalamic neurons, as evidenced by mobilization of extracellular Ca 2+ . © 2007 Wiley‐Liss, Inc.