Brain Research 981 (2003) 151–159 www.elsevier.com / locate / brainres Research report Central 5-HT and 5-HT receptor stimulation decreases salt 2B/2C 3 intake in sodium-depleted rats a a a a ´ ´ Letıcia Castro , Rodrigo Athanazio , Marcelo Barbetta , Ana Claudia Ramos , a a a b ˜ Ana Luiza Angelo , Igor Campos , Bruno Varjao , Hilda Ferreira , a a, * Josmara Fregoneze , Emilio de Castro e Silva a Department of Physiology, Health Sciences Institute, Federal University of Bahia, 40110-100 Salvador—Bahia, Brazil b Life Sciences Department, Bahia State University, 41195-001 Salvador—Bahia, Brazil Accepted 14 May 2003 Abstract In the present study, we investigated the participation of central 5-HT and 5-HT receptors in the salt intake induced by sodium 2B/2C 3 depletion in Wistar male rats. Sodium depletion was produced by the administration of furosemide associated with a low salt diet. Third ventricle injections of mCPP, a 5-HT agonist, at doses of 80, 160 and 240 nmol, promoted a dose-dependent reduction in salt intake 2B/2C in sodium-depleted rats. The inhibitory effect produced by central administration of mCPP was abolished by the central pretreatment with SDZ SER 082, a 5-HT antagonist. Similar results were obtained with third ventricle injections of m-CPBG (80, 160 and 240 nmol), 2B/2C a selective 5-HT agonist that also induced a dose-related decrease in salt intake in sodium-depleted rats. The central pretreatment with 3 LY-278,584, a selective 5-HT receptor antagonist, was able to impair the salt intake inhibition elicited by third ventricle injections of 3 m-CPBG. Central administration of each one of the antagonists alone or a combination of both antagonists together did not significantly change salt intake after sodium depletion. On the other hand, the central administration of both mCPP and m-CPBG, in the highest dose used to test their effect on salt intake (240 nmol), was unable to modify blood pressure in sodium-depleted rats. It is concluded that: (1) pharmacological activation of central 5-HT and 5-HT receptors diminishes salt intake during sodium depletion, (2) an inhibitory 2B/2C 3 endogenous drive exerted by central 5-HT and 5-HT receptors does not seem to exist and (3) the reduction in salt intake generated 2B/2C 3 by the pharmacological activation of these central receptors is not produced by an acute hypertensive response.  2003 Elsevier B.V. All rights reserved. Theme: Neural basis of behavior Topic: Ingestive behaviors Keywords: Sodium appetite; Serotonin; Sodium depletion 1. Introduction both osmolarity and blood pressure, results from very fine regulatory actions adjusting the intake / excretion balance Osmolarity and blood pressure control in mammals is of water and sodium. The sodium intake / excretion balance achieved by the action of multiple regulatory loops induc- is mainly dependent on two complementary parameters— ing endocrine, nervous and behavioral effects designed to sodium appetite and renal sodium excretion—that are maintain those parameters within their narrow physiologi- strongly controlled by the central nervous system [20]. cal ranges [4]. Brain serotonin circuitries are clearly involved in the Sodium homeostasis, a necessary step in the control of control of sodium appetite, the crucial motivation inducing sodium intake. Indeed, serotonin pathways in lateral parabrachial nucleus seem to exert a tonic inhibition in salt *Corresponding author. Tel.: 155-71-235-7518; fax: 155-71-337- intake induced by sodium depletion [24] or by the stimula- 0591. E-mail address: emilio@ufba.br (E. de Castro e Silva). tion of prosencephalic angiotensinergic pathways [11]. 0006-8993 / 03 / $ – see front matter  2003 Elsevier B.V. All rights reserved. doi:10.1016 / S0006-8993(03)03015-4