Vasopressin is a major vasoconstrictor involved in hindlimb vascular responses to stimulation of adenosine A1 receptors in the nucleus of the solitary tract

AUTOR(ES)

McClure, Joseph M.

FONTE

American Physiological Society

RESUMO

Our previous study showed that stimulation of adenosine A1 receptors located in the nucleus of the solitary tract (NTS) exerts counteracting effects on the iliac vascular bed: activation of the adrenal medulla and β-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 A1 receptor agonist N6-cyclopentyladenosine (CPA; 330 pmol in 50 nl) in intact (Int) animals and following: V1 vasopressin receptor blockade (VX), angiotensin II AT1 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 A1 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 A1 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 β-adrenergic vasodilation in iliac vascular responses triggered by stimulation of NTS A1 adenosine receptors, whereas angiotensin II and norepinephrine do not contribute significantly to the vasoconstrictor responses.

Documentos Relacionados

• Enhanced tubuloglomerular feedback in mice with vascular overexpression of A1 adenosine receptors
• A1 adenosine receptors mediate hypoxia-induced ventriculomegaly
• Adenosine acts by A1 receptors to stimulate release of prolactin from anterior-pituitaries in vitro
• The vasopressin mRNA poly(A) tract is unusually long and increases during stimulation of vasopressin gene expression in vivo.
• Characteristics of Rostral Solitary Tract Nucleus Neurons With Identified Afferent Connections That Project to the Parabrachial Nucleus in Rats