Functional characterization of adenosine receptors in the nucleus tractus solitarius mediating hypotensive responses in the rat

Abstract

1The aim of this study was to characterize adenosine receptors located in the nucleus tractus solitarius (NTS) that mediate decreases in blood pressure in the anaesthetized rat. To determine the adenosine receptor subtype involved, a range of selective agonists and antagonists were studied and their relative potencies evaluated. 2 The rank order of agonist potency in inducing decreases in diastolic blood pressure was N6-3 The hypotensive action of CPA following microinjection into the NTS was antagonized by i.v. infusions (50 Mug kg-' min-') of adenosine receptor antagonists, 8-cyclopentyl-1,3 dipropylxanthine (DPCPX), 8-phenyltheophylline (8-PT), 8-(p-sulphophenyl)theophylline (8-SPT), and 1,3-dipropyl-8-N-(2-(diethylamino)ethyl)-N methyl-4-(2,3,6,7-tetrahydro-2,6-dioxo) benzenesulphonamidexanthine (PD 115199). The antagonist potency order was DPCPX>PD115199 >8-PT. Intravenous infusion of 8-SPT had no effect on blood pressure responses to microinjection of CPA into the NTS.4 The results suggest that adenosine Al receptors in the NTS mediate hypotensive responses in the anaesthetized rat preparation.

Mechanisms mediating regional sympathoactivatory responses to stimulation of NTS A1 adenosine receptors

“…Previous studies have shown that stimulation of NTS A 1 receptors evokes variable hemodynamic effects: it usually increases MAP in a dose-dependent manner, whereas HR slightly decreases (1); however, the depressor effects also have been reported (36). There is also evidence that adenosine A 1 receptors located in the NTS and rostral ventrolateral medulla play a role in hypothalamic defense response facilitating the pressor component (30,31).…”

Chronic Caffeine Treatment Causes Changes in Cardiac Adenosine Receptor Function in Rats

“…Activation of adenosine A 1 receptors produces negative inotropy, chronotropy and dromotropy, inhibition of renin release and inhibition of catecholamine release via an action in the cardiovascular control centre [6][7][8] and diuresis via reduced tubular sodium reabsorption [9]. A 2a receptor activation produces most notably dilation of coronary blood vessels [10].…”

Natural Protection Against Cardiac Arrhythmias During Hibernation: Significance of Adenosine

“…NTS influences cardiovascular system. Hypotensive responses in the cardiovascular system are mediated through A 1 AR in NTS (White et al, 1996). Adenosine microinjections into the NTS result in a slow and regulated decrease in heart rate (Tseng et al, 1995;Phillis et al, 1997;Ho et al, 2008).…”