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This Article Full Text Full Text (PDF) All Versions of this Article: 92/5/923    most recent expphysiol.2007.037317v1 Alert me when this article is cited Alert me if a correction is posted 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 Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Cedraz-Mercez, P. L. Articles by Reis, L. C. Search for Related Content PubMed PubMed Citation Articles by Cedraz-Mercez, P. L. Articles by Reis, L. C.

¹ Department of Physiological Sciences, Biology Institute, Federal Rural University of Rio de Janeiro, BR465, Km 7, 23890-000, Seropédica, RJ, Brazil

The present study was carried out to assess the influence of noradrenergic stimulation of the midbrain dorsal (DRN) and median raphe nuclei (MRN) on urinary volume and electrolyte excretion in hydrated rats. Wistar rats were implanted with a guide cannula into the MRN or DRN and then submitted to two intragastric administrations of water in order to attain an increased diuresis. The following treatments were performed. (1) Intra-DRN microinjections of saline (0.2 µl), ₁-adrenergic agonist phenylephrine (PHE, 0.49 and 4.9 nmol in 0.2 µl), ₂-adrenergic antagonist idazoxan (IDZ, 0.42 and 4.2 nmol in 0.2 µl) or the ₁-adrenergic antagonist prazosin (PRZ, 0.24 and 2.4 nmol in 0.2 µl). (2) Intra-MRN microinjections of saline, IDZ (4.2 nmol in 0.2 µl), PHE (4.9 nmol in 0.2 µl) or PRZ (2.4 nmol in 0.2 µl). Urine samples were subsequently collected over 120 min at 20 min intervals for photometric measurement of sodium and potassium. Intra-DRN administration of PHE and IDZ significantly increased the urinary volume, natriuresis and kaliuresis. Intra-DRN microinjection of a higher dose of PRZ reduced the urinary volume and both sodium and potassium excretion. Intra-MRN microinjections of PHE, IDZ or PRZ did not induce any significant effect on urinary volume or electrolyte excretion. These data suggest that the increase of tonic excitatory noradrenergic input conveyed to DRN influences the hydroelectrolyte homeostasis, possibly through 5-HTergic circuitry.

(Received 15 February 2007; accepted after revision 19 June 2007; first published online 25 June 2007)
Corresponding author L. C. Reis: Department of Physiological Sciences, Biology Institute, Federal Rural University of Rio de Janeiro, BR465, Km 7, 23890-000, Seropédica, RJ, Brazil. Email: lcreis{at}ufrrj.br