Investigation of the Role of AT2 Receptors in the Nucleus Tractus Solitarii of Normotensive Rats in Blood Pressure Control

The nucleus tractus solitarii (NTS) densely expresses angiotensin II type 2 receptors (AT2R), which are mainly located on inhibitory gamma-aminobutyric acid (GABA) neurons. Central AT2R stimulation reduces blood pressure, and AT2R stimulation in the rostral ventrolateral medulla (RVLM), mediates a h...

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Bibliographic Details
Published in:Frontiers in neuroscience 2019-06, Vol.13, p.589-589
Main Authors: Légat, Laura, Smolders, Ilse J, Dupont, Alain G
Format: Article
Language:English
Subjects:
Amino acids
Angiotensin
Angiotensin II
angiotensin II type 2 receptor
Blood pressure
Brain research
Chromatography
Compound 21
gamma-aminobutyric acid
Heart
Heart rate
Hypertension
Hypotheses
mean arterial blood pressure
Medulla oblongata
Microdialysis
Neuroscience
nucleus tractus solitarii
Perfusion
renin-angiotensin–aldosterone system
Rodents
Solitary tract nucleus
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Summary:The nucleus tractus solitarii (NTS) densely expresses angiotensin II type 2 receptors (AT2R), which are mainly located on inhibitory gamma-aminobutyric acid (GABA) neurons. Central AT2R stimulation reduces blood pressure, and AT2R stimulation in the rostral ventrolateral medulla (RVLM), mediates a hypotensive response through a GABAergic mechanism. We aimed to test the hypothesis that an AT2R mediated inhibition of the GABA release within the NTS might be involved in this hypotensive response, by assessing possible alterations in blood pressure and heart rate, as well as in GABA levels in normotensive Wistar rats. microdialysis was used for measurement of extracellular GABA levels and for perfusion of the selective AT2R agonist, Compound 21, within the NTS. Our set-up allowed to determine simultaneously the excitatory glutamate dialysate levels. The mean arterial pressure and heart rate responses were monitored with a pressure transducer. Local perfusion of Compound 21 into the NTS did not modify blood pressure and heart rate, nor glutamate and GABA levels compared to baseline concentrations. A putative effect was also not unmasked by concomitant angiotensin II type 1 receptor blockade with candesartan. Positive control experiments confirmed that the experimental set up had enough sensitivity to detect a reduction in GABA dialysate levels and blood pressure. The results did not provide evidence for a role of the AT2R within the NTS in the control of blood pressure, nor for an interaction with local GABAergic signaling in normotensive rats.
ISSN:1662-4548
1662-453X
1662-453X
DOI:10.3389/fnins.2019.00589