Journal
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Volume 297, Issue 5, Pages H1661-H1672Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.00432.2009
Keywords
purinergic receptors; V-1 receptor blockade; angiotensin II type 1 receptor blockade; ganglionic blockade; adrenalectomy; lumbar sympathectomy; iliac vascular conductance
Funding
- National Heart, Lung, and Blood Institute [HL-67814]
- Merit Review Award by Department of Veterans Affairs
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McClure JM, Rossi NF, Chen H, O'Leary DS, Scislo TJ. Vasopressin is a major vasoconstrictor involved in hindlimb vascular responses to stimulation of adenosine A(1) receptors in the nucleus of the solitary tract. Am J Physiol Heart Circ Physiol 297: H1661-H1672, 2009. First published September 11, 2009; doi:10.1152/ajpheart.00432.2009. Our previous study showed that stimulation of adenosine A(1) receptors located in the nucleus of the solitary tract (NTS) exerts counteracting effects on the iliac vascular bed: activation of the adrenal medulla and beta-adrenergic vasodilation versus vasoconstriction mediated by neural and unknown humoral factors. In the present study we investigated the relative contribution of three major potential humoral vasoconstrictors: vasopressin, angiotensin II, and norepinephrine in this response. In urethane-chloralose anesthetized rats we compared the integral changes in iliac vascular conductance evoked by microinjections into the NTS of the selective A(1) receptor agonist N-6-cyclopentyladenosine (CPA; 330 pmol in 50 nl) in intact (Int) animals and following: V-1 vasopressin receptor blockade (VX), angiotensin II AT(1) receptor blockade (ATX), bilateral adrenalectomy + ganglionic blockade (ADX + GX; which eliminated the potential increases in circulating norepinephrine and epinephrine), ADX + GX + VX and ADX + GX + VX + ATX. In Int animals, stimulation of NTS A(1) adenosine receptors evoked typical variable responses with prevailing pressor and vasoconstrictor effects. VX reversed the responses to depressor ones. ATX did not significantly alter the responses. ADX + GX accentuated pressor and vasoconstrictor responses, whereas ADX + GX + VX and ADX + GX + VX + ATX virtually abolished the responses. Stimulation of NTS A(1) adenosine receptors increased circulating vasopressin over fourfold (26.4 +/- 10.4 vs. 117.0 +/- 19 pg/ml). These data strongly suggest that vasopressin is a major vasoconstrictor factor opposing beta-adrenergic vasodilation in iliac vascular responses triggered by stimulation of NTS A(1) adenosine receptors, whereas angiotensin II and norepinephrine do not contribute significantly to the vasoconstrictor responses.
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