A1 noradrenergic neurons lesions reduce natriuresis and hypertensive responses to hypernatremia in rats
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2013-09
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Noradrenergic neurons in the caudal ventrolateral medulla (CVLM; A1 group) contribute to cardiovascular regulation. The
present study assessed whether specific lesions in the A1 group altered the cardiovascular responses that were evoked by
hypertonic saline (HS) infusion in non-anesthetized rats. Male Wistar rats (280–340 g) received nanoinjections of
antidopamine-b-hydroxylase-saporin (A1 lesion, 0.105 ng.nL 21 ) or free saporin (sham, 0.021 ng.nL 21 ) into their CVLMs. Two
weeks later, the rats were anesthetized (2% halothane in O 2 ) and their femoral artery and vein were catheterized and led to
exit subcutaneously between the scapulae. On the following day, the animals were submitted to HS infusion (3 M NaCl,
1.8 ml N kg 21 , b.wt., for longer than 1 min). In the sham-group (n = 8), HS induced a sustained pressor response (DMAP:
3563.6 and 1161.8 mmHg, for 10 and 90 min after HS infusion, respectively; P,0.05 vs. baseline). Ten min after HS
infusion, the pressor responses of the anti-DbH-saporin-treated rats (n = 11)were significantly smaller(DMAP: 1861.4 mmHg;
P,0.05 vs. baseline and vs. sham group), and at 90 min, their blood pressures reached baseline values (261.6 mmHg).
Compared to the sham group, the natriuresis that was induced by HS was reduced in the lesioned group 60 min after the
challenge (19665.5 mM vs. 26267.6 mM, respectively; P,0.05). In addition, A1-lesioned rats excreted only 47% of their
sodium 90 min after HS infusion, while sham animals excreted 80% of their sodium. Immunohistochemical analysis
confirmed a substantial destruction of the A1 cell group in the CVLM of rats that had been nanoinjected withanti-DbH-
saporin. These results suggest that medullary noradrenergic A1 neurons are involved in the excitatory neural pathway that
regulates hypertensive and natriuretic responses to acute changes in the composition of body fluid.
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SILVA, Elaine Fernanda da; FREIRI-OLIVEIRA, André Henrique; CUSTODIO, Carlos Henrique Xavier; GHEDINI, Paulo César; BATAUS, Luiz Artur Mendes; COLOMBARI, Eduardo; CASTRO, Carlos Henrique de; COLUGNATI, Diego Basile; ROSA, Daniel Alves; CRAVO, Sergio L. D.; PEDRINO, Gustavo Rodrigues. A1 noradrenergic neurons lesions reduce natriuresis and hypertensive responses to hypernatremia in rats. Plos One, San Francisco, v. 8, n. 9, e73187, Sept. 2013.