A2 noradrenergic lesions prevent renal sympathoinhibition induced by hypernatremia in rats
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2012-05
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Renal vasodilation and sympathoinhibition are recognized responses induced by hypernatremia, but the central neural
pathways underlying such responses are not yet entirely understood. Several findings suggest that A2 noradrenergic
neurons, which are found in the nucleus of the solitary tract (NTS), play a role in the pathways that contribute to body fluid
homeostasis and cardiovascular regulation. The purpose of this study was to determine the effects of selective lesions of A2
neurons on the renal vasodilation and sympathoinhibition induced by hypertonic saline (HS) infusion. Male Wistar rats (280–
350 g) received an injection into the NTS of anti-dopamine-beta-hydroxylase-saporin (A2 lesion; 6.3 ng in 60 nl; n = 6) or
free saporin (sham; 1.3 ng in 60 nl; n = 7). Two weeks later, the rats were anesthetized (urethane 1.2 g?kg 21 b.wt., i.v.) and
the blood pressure, renal blood flow (RBF), renal vascular conductance (RVC) and renal sympathetic nerve activity (RSNA)
were recorded. In sham rats, the HS infusion (3 M NaCl, 1.8 ml?kg 21 b.wt., i.v.) induced transient hypertension (peak at
10 min after HS; 962.7 mmHg) and increases in the RBF and RVC (14167.9% and 14067.9% of baseline at 60 min after HS,
respectively). HS infusion also decreased the RSNA (24565.0% at 10 min after HS) throughout the experimental period. In
the A2-lesioned rats, the HS infusion induced transient hypertension (661.4 mmHg at 10 min after HS), as well as increased
RBF and RVC (13365.2% and 13466.9% of baseline at 60 min after HS, respectively). However, in these rats, the HS failed to
reduce the RSNA (11563.1% at 10 min after HS). The extent of the catecholaminergic lesions was confirmed by
immunocytochemistry. These results suggest that A2 noradrenergic neurons are components of the neural pathways
regulating the composition of the extracellular fluid compartment and are selectively involved in hypernatremia-induced
sympathoinhibition.
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PEDRINO, Gustavo Rodrigues; FREIRIA-OLIVEIRA, André Henrique; COLOMBARI, Débora Simões Almeida; ROSA, Daniel Alves ; CRAVO, Sergio Luiz. A2 noradrenergic lesions prevent renal sympathoinhibition induced by hypernatremia in rats. Plos One, San Francisco, v. 7, n. 5, e37587, May 2012.