Adrenergic mechanisms of the Kölliker-Fuse/A7 area on the control of water and sodium intake

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The blockade of serotoninergic receptors with methysergide or the activation of alpha(2)-adrenoceptors with moxonidine into the lateral parabrachial nucleus (LPBN) increases water and 0.3 M NaCl intake in rats treated with furosemide (FURO) combined with captopril (CAP). In the present study we investigated the effects of bilateral injections of noradrenaline (the endogenous neurotransmitter for alpha-adrenoceptors) alone or combined with the alpha(2)-adrenoceptor antagonist RX 821002 into the LPBN or into the rostral portion of the Kolliker-Fuse nucleus that includes also the A7 area (KF/A7 area) on FURO+CAP-induced water and 0.3 M NaCl intake. Male Holtzman rats with bilateral stainless steel guide-cannulas implanted into KF/A7 area or LPBN were used. FURO+CAP-induced 0.3 M NaCl intake strongly increased after bilateral injections of noradrenaline (80 or 160 nmol/0.2 mu l) into LPBN (26.5 +/- 5.9 and 20.7 +/- 2.0 ml/2 h versus saline: 4.4 +/- 0.9 ml/2 h) or into the KF/A7 area (31.5 +/- 6.1 and 25.9 +/- 4.7 ml/2 h versus saline: 7.2 +/- 1.6 ml/2 h). Water intake increased with noradrenaline injected in KF/A7 area, however, this treatment reduced 0.06 M sucrose intake, suggesting that the increase of water and NaCl intake is not related to non-specific effect. Bilateral injections of RX 821002 (160 nmol/0.2 mu l) into LPBN or KF/A7 area abolished the effects of noradrenaline (160 nmol/0.2 mu l) in the same areas on 0.3 M NaCl intake (7.5 +/- 2.5 and 9.8 +/- 4.4 ml/2 h, respectively). Moxonidine (0.5 nmol/0.2 mu l) injected bilaterally into the KF/A7 area increased 0.3 M NaCl intake (39.5 +/- 6.3 ml/3 h) and water intake, while methysergide (4 mu g/0.2 mu l) into the KF/A7 area did not alter 0.3 M NaCl or water intake. The results suggest that alpha(2)-adrenoceptor activation is a common mechanism in the KF/A7 area and LPBN to facilitate sodium intake. However, the serotonergic mechanism is present in LPBN, not in the KF/A7 area. (C) 2009 IBRO. Published by Elsevier Ltd. All rights reserved.