Key result
Chronic intracerebroventricular infusion of Angiotensin II significantly increased mean arterial pressure from 87 to 109 mmHg and enhanced GABAB receptor expression in the nucleus tractus solitarii of rats.
Chronic central administration of Angiotensin II increases blood pressure and selectively enhances functional GABA(B) receptor expression and inhibitory GABAergic neurotransmission in the NTS of rats.
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.
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Zhang et al. (2009) studied Hypertension (Animal Model). Angiotensin II (ANG II) vs. Artificial cerebrospinal fluid (aCSF) was evaluated on Mean arterial pressure (MAP) (p=<0.05). Chronic intracerebroventricular infusion of Angiotensin II significantly increased mean arterial pressure from 87 to 109 mmHg and enhanced GABAB receptor expression in the nucleus tractus solitarii of rats.
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