title: Importance of central AT₁ receptors for sodium intake induced by GABAergic activation of the lateral parabrachial nucleus.
abstract: The blockade of the inhibitory mechanisms for sodium intake with GABAergic activation in the lateral parabrachial nucleus (LPBN) induces strong ingestion of water and hypertonic NaCl in satiated and normovolemic rats. A question that remains is if the activity of facilitatory mechanisms, like angiotensin II, is necessary for sodium and water intake induced by muscimol (GABA(A) receptor agonist) injected into the LPBN. Therefore, in the present study, we investigated the effects of the blockade of angiotensinergic AT(1) receptors with losartan injected i.c.v. on 0.3 M NaCl and water intake induced by muscimol injected into the LPBN in satiated and normovolemic rats. Male Holtzman rats with stainless steel cannulas implanted bilaterally into the LPBN and unilaterally into the lateral ventricle were used. Bilateral injections of muscimol (0.5 nmol/0.2 μl) into the LPBN combined with i.c.v. injection of vehicle induced 0.3 M NaCl (31.7 ± 1.8 ml/240 min, vs. saline: 0.4 ± 0.3 ml/240 min) and water intake (21.5 ± 1.9 ml/240 min, vs. saline: 0.8 ± 0.2 ml/240 min). Losartan (50 and 100 μg/1.0 μl) injected i.c.v. reduced the effects of LPBN-muscimol on 0.3 M NaCl (18.9 ± 1.9 and 9.9 ± 1.7 ml/240 min, respectively) and water intake (9.8 ± 1.7 and 5.1 ± 1.1 ml/240 min, respectively). The results suggest that the activation of central AT(1) angiotensinergic receptors is essential for hypertonic NaCl and water intake induced by the blockade of the inhibitory mechanisms with muscimol injected into the LPBN in satiated and normovolemic rats.
authors: Department of Physiology and Pathology, School of Dentistry, São Paulo State University, UNESP, Araraquara, São Paulo, Brazil.
authors: C F
authors: CF
authors: Roncari
authors: R B
authors: RB
authors: David
authors: P M
authors: PM
authors: de Paula
authors: D S A
authors: DS
authors: Colombari
authors: L A
authors: LA
authors: de Luca
authors: J V
authors: JV
authors: Menani
mesh_terms: D000804:Angiotensin II / Q000502:physiology; D047228:Angiotensin II Type 1 Receptor Blockers / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D004326:Drinking / Q000187:drug effects / Q000502:physiology*; D058785:GABA-A Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D007276:Injections, Intraventricular; D019808:Losartan / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008845:Microinjections; D009118:Muscimol / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011149:Pons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012462:Saline Solution, Hypertonic
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D058785:GABA-A Receptor Agonists; D012462:Saline Solution, Hypertonic; D000804:Angiotensin II; D009118:Muscimol; D019808:Losartan