title: Chronic excitotoxic lesion of the dorsal raphe nucleus induces sodium appetite.
abstract: We determined if the dorsal raphe nucleus (DRN) exerts tonic control of basal and stimulated sodium and water intake. Male Wistar rats weighing 300-350 g were microinjected with phosphate buffer (PB-DRN, N = 11) or 1 microg/0.2 microl, in a single dose, ibotenic acid (IBO-DRN, N = 9 to 10) through a guide cannula into the DRN and were observed for 21 days in order to measure basal sodium appetite and water intake and in the following situations: furosemide-induced sodium depletion (20 mg/kg, sc, 24 h before the experiment) and a low dose of dietary captopril (1 mg/g chow). From the 6th day after ibotenic acid injection IBO-DRN rats showed an increase in sodium appetite (12.0 +/- 2.3 to 22.3 +/- 4.6 ml 0.3 M NaCl intake) whereas PB-DRN did not exceed 2 ml (P < 0.001). Water intake was comparable in both groups. In addition to a higher dipsogenic response, sodium-depleted IBO-DRN animals displayed an increase of 0.3 M NaCl intake compared to PB-DRN (37.4 +/- 3.8 vs 21.6 +/- 3.9 ml 300 min after fluid offer, P < 0.001). Captopril added to chow caused an increase of 0.3 M NaCl intake during the first 2 days (IBO-DRN, 33.8 +/- 4.3 and 32.5 +/- 3.4 ml on day 1 and day 2, respectively, vs 20.2 +/- 2.8 ml on day 0, P < 0.001). These data support the view that DRN, probably via ascending serotonergic system, tonically modulates sodium appetite under basal and sodium depletion conditions and/or after an increase in peripheral or brain angiotensin II.
authors.affiliation: Departamento de Ciências Fisiológicas, Instituto de Biologia, Universidade Federal Rural do Rio de Janeiro, Seropédica, RJ, Brazil.
authors.forename: H R
authors.initials: HR
authors.lastname: Cavalcante-Lima
authors.forename: D
authors.initials: D
authors.lastname: Badauê-Passos
authors.forename: W
authors.initials: W
authors.lastname: de-Lucca
authors.forename: H R C
authors.initials: HR
authors.lastname: Lima
authors.forename: R H
authors.initials: RH
authors.lastname: Costa-e-Sousa
authors.forename: E L
authors.initials: EL
authors.lastname: Olivares
authors.forename: P L
authors.initials: PL
authors.lastname: Cedraz-Mercez
authors.forename: R O
authors.initials: RO
authors.lastname: Reis
authors.forename: M A
authors.initials: MA
authors.lastname: Medeiros
authors.forename: W S
authors.initials: WS
authors.lastname: Côrtes
authors.forename: L C
authors.initials: LC
authors.lastname: Reis
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D001066:Appetite / Q000187:drug effects* / Q000502:physiology; D002021:Buffers; D002216:Captopril / Q000494:pharmacology; D004326:Drinking / Q000187:drug effects* / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity*; D005665:Furosemide / Q000494:pharmacology; D007051:Ibotenic Acid / Q000633:toxicity*; D008297:Male; D010710:Phosphates; D011903:Raphe Nuclei / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000494:pharmacology; D012982:Sodium, Dietary; D013997:Time Factors
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D002021:Buffers; D018690:Excitatory Amino Acid Agonists; D010710:Phosphates; D049994:Sodium Potassium Chloride Symporter Inhibitors; D012982:Sodium, Dietary; D007051:Ibotenic Acid; D005665:Furosemide; D002216:Captopril