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This Article Full Text Full Text (PDF) Buy All Versions of this Article: 297/5/H1837    most recent 00354.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Zhang, Q. Articles by Sun, C. PubMed PubMed Citation Articles by Zhang, Q. Articles by Sun, C.

Angiotensin II enhances GABA_B receptor-mediated responses and expression in nucleus tractus solitarii of rats

Department of Pharmaceutical Sciences, College of Pharmacy, North Dakota State University, Fargo, North Dakota

Submitted April 10, 2009 ; accepted in final form September 10, 2009

Angiotensin II (ANG II) increases GABA_B receptor expression in neuronal cultures from the nucleus tractus solitarii (NTS). In the present study, the chronic effects of ANG II on GABA_B receptor expression and activity were examined in the NTS of Sprague-Dawley rats. Intracerebroventricular infusion of ANG II caused a significant elevation in blood pressure (BP) and an increase in GABA_B receptor expression in the NTS. Conversely, chronic N^G-nitro-L-arginine methyl ester (L-NAME) treatment also increased BP, but had no effect on GABA_B receptor expression in the NTS. Next, we examined the BP response to the GABA_B receptor agonist baclofen microinjected into the NTS of ANG II- or artificial cerebrospinal fluid (aCSF)-infused rats. NTS microinjection of baclofen increased BP in both groups of rats. However, the pressor response to baclofen was enhanced in ANG II-infused rats compared with aCSF-infused rats. In addition, bilateral microinjection of the GABA_B receptor antagonist CGP-35348 into the NTS evoked a decrease in BP in both group of rats, and the depressor responses to CGP-35348 were enhanced in the ANG II-infused rats. In contrast, the pressor responses to the GABA_A receptor agonist muscimol and the depressor responses to the GABA_A receptor antagonist bicuculline were comparable between aCSF- and ANG II-infused rats. These results indicate that chronic ANG II infusion stimulates GABA_B receptor expression and augments GABA_B receptor-mediated responses in the NTS. This effect could contribute to the central nervous system actions of ANG II that result in dampening of baroreflexes and elevation in arterial BP.

hypertension; -aminobutyric acid; blood pressure; gene expression