title: Moxonidine into the lateral parabrachial nucleus reduces renal and hormonal responses to cell dehydration.
abstract: The deactivation of the inhibitory mechanisms with injections of moxonidine (α2-adrenoceptor/imidazoline receptor agonist) into the lateral parabrachial nucleus (LPBN) increases hypertonic NaCl intake by intra- or extracellular dehydrated rats. In the present study, we investigated the changes in the urinary sodium and volume, sodium balance, and plasma vasopressin and oxytocin in rats treated with intragastric (i.g.) 2 M NaCl load (2 ml/rat) combined with injections of moxonidine into the LPBN. Male Holtzman rats (n=5-12/group) with stainless steel cannulas implanted bilaterally into LPBN were used. Bilateral injections of moxonidine (0.5 nmol/0.2 μl) into the LPBN decreased i.g. 2 M NaCl-induced diuresis (4.6±0.7 vs. vehicle: 7.4±0.6 ml/120 min) and natriuresis (1.65±0.29 vs. vehicle: 2.53±0.17 mEq/120 min), whereas the previous injection of the α2-adrenoceptor antagonist RX 821002 (10 nmol/0.2 μl) into the LPBN abolished the effects of moxonidine. Moxonidine injected into the LPBN reduced i.g. 2 M NaCl-induced increase in plasma oxytocin and vasopressin (14.6±2.8 and 2.2±0.3 vs. vehicle: 25.7±7 and 4.3±0.7 pg/ml, respectively). Moxonidine injected into the LPBN combined with i.g. 2 M NaCl also increased 0.3 M NaCl intake (7.5±1.7 vs. vehicle: 0.5±0.2 mEq/2 h) and produced positive sodium balance (2.3±1.4 vs. vehicle: -1.2±0.4 mEq/2 h) in rats that had access to water and NaCl. The present results show that LPBN α2-adrenoceptor activation reduces renal and hormonal responses to intracellular dehydration and increases sodium and water intake, which facilitates sodium retention and body fluid volume expansion.
authors.affiliation: Department of Physiology and Pathology, School of Dentistry, São Paulo State University, UNESP, Rua Humaitá, 1680, Centro, 14801-903 Araraquara, SP, Brazil. carina.andrade@foar.unesp.br
authors.forename: C A F
authors.initials: CA
authors.lastname: Andrade
authors.forename: L O
authors.initials: LO
authors.lastname: Margatho
authors.forename: G M F
authors.initials: GM
authors.lastname: Andrade-Franzé
authors.forename: L A
authors.initials: LA
authors.lastname: De Luca
authors.forename: J
authors.initials: J
authors.lastname: Antunes-Rodrigues
authors.forename: J V
authors.initials: JV
authors.lastname: Menani
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood; D009320:Atrial Natriuretic Factor / Q000097:blood; D001810:Blood Volume / Q000187:drug effects; D001917:Brachial Plexus; D003681:Dehydration / Q000378:metabolism* / Q000473:pathology; D004231:Diuresis / Q000187:drug effects; D006728:Hormones / Q000097:blood*; D019329:Idazoxan / Q000031:analogs & derivatives / Q000494:pharmacology; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D054755:Imidazoline Receptors / Q000008:administration & dosage / Q000819:agonists*; D007668:Kidney / Q000166:cytology / Q000187:drug effects*; D008297:Male; D009318:Natriuresis / Q000187:drug effects; D009994:Osmolar Concentration; D010121:Oxytocin / Q000097:blood; D011188:Potassium / Q000652:urine; D051381:Rats; D017207:Rats, Sprague-Dawley; D012083:Renin / Q000097:blood; D012964:Sodium / Q000097:blood / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D014882:Water-Electrolyte Balance / Q000187:drug effects
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D000317:Adrenergic alpha-Antagonists; D006728:Hormones; D007093:Imidazoles; D054755:Imidazoline Receptors; D001127:Arginine Vasopressin; D012965:Sodium Chloride; D010121:Oxytocin; D009320:Atrial Natriuretic Factor; D012964:Sodium; C043482:moxonidine; C058525:2-methoxyidazoxan; D012083:Renin; D011188:Potassium; D019329:Idazoxan