alpha(2)-Adrenoceptor-Mediated Inhibition of Catecholamine Release from the Adrenal Medulla of Spontaneously Hypertensive Rats is Preserved in the Early Stages of Hypertension

• Type: Article in International Scientific Journal
• Date: 2011

Authors

moura, e (Author) Other; pinto, ce (Author) Other; calo, a (Author) Other; serrao, mp (Author) Other; afonso, j (Author) Other; vieira-coelho, ma (Author) FMUP

Journal

Title: Basic and Clinical Pharmacology and Toxicology

Vol. 109

Pages: 253-260

ISSN: 1742-7835

Publisher: Wiley-Blackwell

Indexing

ISI Web of Knowledge - 5 Citations

Scopus - 5 Citations

Scientific classification

FOS: Medical and Health sciences > Basic medicine

Other information

Authenticus ID: P-002-MA7

DOI: 10.1111/j.1742-7843.2011.00712.x

Abstract (EN): In this study, we evaluated the effect of alpha(2)-adrenoceptor activation on catecholamine release from the adrenal medulla of pre-hypertensive (6-week-old) and hypertensive (16-week-old) spontaneously hypertensive rats (SHR) and of age-matched normotensive control Wistar Kyoto (WKY) rats. Catecholamine overflow from isolated adrenal medullae was evoked by the nicotinic receptor agonist 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP) in the absence and presence of the alpha(2)-adrenoceptor agonist medetomidine (MED). The spontaneous outflow of adrenaline was similar between age-matched SHR and WKY rats. However, the spontaneous outflow of noradrenaline was significantly lower in SHR compared with age-matched WKY rats. DMPP (0.1-3 mM) increased the outflow of noradrenaline and adrenaline in a concentration-dependent manner. The E-max values for adrenaline overflow were similar between strains, but the E-max values for noradrenaline overflow were significantly lower in SHR. The EC50 values for noradrenaline and adrenaline overflow were significantly higher in SHR compared with age-matched WKY rats. MED (0.1-300 nM) reduced the DMPP-evoked overflow (DMPP 500 mu M) of noradrenaline and adrenaline in a concentration-dependent manner and was capable of totally inhibiting this effect. The inhibitory action of MED was similar between age-matched SHR and WKY rats. In the adrenals, the alpha(2A)- and alpha(2B)-adrenoceptor subtypes had the highest mRNA expression levels; the alpha(2C)-adrenoceptor subtype had the lowest mRNA expression levels. The mRNA levels for the three subtypes were similar between strains. In conclusion, in SHR during the development of hypertension, adrenal alpha(2)-adrenoceptor inhibitory function is conserved, accompanied by reduced noradrenaline release and unchanged adrenaline release.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8