Blackwell Publishing Journal Backfiles 1879-2005
1. The modulatory actions of both adenosine A1 and K1-opioid receptor agonists on β-adrenoceptor stimulation in the heart of both spontaneously hypertensive rats (SHR) and nor-motensive Wistar-Kyoto (WKY) rats were compared.2. In both types of rats, bot. R(-)-N6-(2-phenyliso-propyl)adenosine (R-PIA), an adenosine A1 receptor agonist, and U50 488H, a K1-opioid receptor agonist, inhibited the stimulatory effects of β-adrenoceptor activation on electrically induced [Ca2+]i transients measured by a spectrofluorometric method with fura-2/AM as the calcium indicator. The effects of these two agonists were blocked by their respective antagonists, namely 8-cyclopentyl-l,3-diprolxanthine and norbinaltorphimine.3. The inhibitory actions of both R-PIA and U50488H on β-adrenoceptor augmentation of electrically induce. [Ca2+]i transients in the heart were more significantly reduced in SHR than in WKY rats, suggesting the negative modulatory actions of endogenous substances on 3-adrenoceptors were impaired in SHR, which may contribute to hypertension.
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