Norepinephrine stimulates immunoreactive (Ir) atrial natriuretic peptide (anp) secretion and pro-anp mrna expression from rat hypothalamic neurons in culture: Effects of α2-adrenoceptors

Weiqing Huang, Dan Lee, Zhiyu Yang, David L. Copolov, Alan T. Lim

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23 Citations (Scopus)

Abstract

Although ANP or its smaller congeners are produced and secreted from rat hypothalami, the role or roles of neurotransmitter(s) in regulating their release and production from the neurons remains unclear. We report here that norepinephrine or epinephrine (NE/EPI) facilitates irANP secretion and pro-ANP mRNA expression in long term cultures of rat hypothalamic neurons through their effects on (α2-adrenoceptors. Hypothalami of 3 day-old Sprague-Dawley rats were removed and digested with collagenase. The dispersed cells were plated on poty-D-tysine coated culture dishes (106cells/well) in Hepes buffered Dulbecco’s Modified Eagle Medium supplemented with 8% fetal calf serum. Six days after plating, media were replenished with serum free media and the cultures incubated for 4 more days with vehicle or various doses of NE, EPI, α- or β-adrenoceptor agonists in the presence or absence of antagonists. Culture media were then extracted with C18Sep-pak and the levels of irANP determined by a well characterised R1A for ANP. NE or EPI treatment significantly increased irANP secretion from the cultures in a dose related manner with ED50and Emaxof approximately 0.2 µM and 1µM respectively. The stimulation effect of NE was blocked by yohimbine (α2-antagonist), but not prazosin (α1-antagonist) or propranolol (β-antagonist). Clonidine (α2-agonist), but not phenylephrine (α2-agonist) or isoprenaline (β-agonist) mimicked the effects of NE or EPI. At the concentration of 0.1 µM, clonidine increased irANP release approximately 3 fold above that of control values (34.7 ± 3.3; mean ± SE, n = 4). These changes were accompanied by corresponding increments in the abundance of pro-ANP mRNA in the cultures as examined by a colorimetric Northern blot analysis. Our results indicate that NE or EPI, acting through its (α2-adrenoceptors, may modulate the function of ANP neurons in rat hypothalami by regulating the secretion and production of the neuropeptide at the genomic level.

Original languageEnglish
Pages (from-to)2426-2428
Number of pages3
JournalEndocrinology
Volume130
Issue number4
DOIs
Publication statusPublished - 1 Jan 1992
Externally publishedYes

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