Differential regulation of central vasopressin receptors in transgenic rats with low brain angiotensinogen

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Item Type:	Article
Title:	Differential regulation of central vasopressin receptors in transgenic rats with low brain angiotensinogen
Creators Name:	Campos, L.A., Couto, A.S., Iliescu, R., Santos, J.A., Santos, R.A.S., Ganten, D., Campagnole-Santos, M.J., Bader, M. and Baltatu, O.
Abstract:	The consequences of permanent alteration to the brain renin-angiotensin system (RAS) on central vasopressinergic system was studied in transgenic rats with low brain angiotensinogen [TGR(ASrAOGEN)]. Levels of vasopressin (AVP) and V1a receptor mRNAs were measured by ribonuclease protection assay (RPA) and AVP by radioimmunoassay (RIA). AVP (100 pmol/50nl) was microinjected into the nucleus tractus solitarii (NTS) of urethane-anesthetized TGR(ASrAOGEN) and Sprague-Dawley (SD) rats and the mean arterial pressure (MAP) and heart rate (HR) baroreflex induced by phenylephrine were evaluated. AVP but not its mRNA levels were significantly lower in the hypothalamus and hypophysis of TGR(ASrAOGEN) rats. Brainstem V1a mRNA levels were significantly higher in TGR(ASrAOGEN) in comparison to SD rats (5.2±0.4% vs. 3.3±0.2% of β-actin mRNA, P<0.05). In contrast, the hypothalamic V1a mRNA levels in TGR(ASrAOGEN) were not different from those found in SD rats. AVP microinjections induced a greater decrease in MAP in TGR(ASrAOGEN) in comparison with SD rats (-19.9±5.2 vs. -7.5±0.7 mm Hg, P<0.01). The significantly higher baroreflex sensitivity observed in TGR compared to that of SD rats was normalized after AVP microinjection. The increased brainstem V1a mRNA levels and sensitivity to AVP in TGR(ASrAOGEN) rats indicates a functional upregulation of AVP receptors in the NTS. The fact that the hypothalamic V1a mRNA levels are not altered indicates that these receptors are differentially regulated in different brain regions. This study demonstrates that a permanent deficit in brain angiotensinogen synthesis can alter the functionality of central vasopressinergic system.
Keywords:	Central Vasopressin Receptors, Transgenic Rats, Brain Angiotensinogen, Animals, Rats
Source:	Regulatory Peptides
ISSN:	0167-0115
Publisher:	Elsevier
Volume:	119
Number:	3
Page Range:	177-182
Date:	15 July 2004
Official Publication:	https://doi.org/10.1016/j.regpep.2004.02.001
PubMed:	View item in PubMed

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