title: Effect of electrolytic lesion of the dorsal raphe nucleus on water intake and sodium appetite.
abstract: The present study determined the effect of an electrolytic lesion of the dorsal raphe nucleus (DRN) on water intake and sodium appetite. Male Wistar rats weighing 290-320 g with a lesion of the DRN (L-DRN), performed two days before experiments and confirmed by histology at the end of the experiments, presented increased sensitivity to the dehydration induced by fluid deprivation. The cumulative water intake of L-DRN rats reached 23.3   1.9 ml (a 79% increase, N = 9) while sham-lesioned rats (SL-DRN) did not exceed 13.0   1.0 ml (N = 11, P < 0.0001) after 5 h. The L-DRN rats treated with isoproterenol (300  g kg-1 ml-1, sc) exhibited an increase in water intake that persisted throughout the experimental period (L-DRN, 15.7   1.47 ml, N = 9 vs SL-DRN, 9.3   1.8 ml, N = 11, P < 0.05). The L-DRN rats also showed an increased spontaneous sodium appetite during the entire period of assessment. The intake of 0.3 M NaCl after 12, 24, 36 and 72 h by the L-DRN rats was always higher than 20.2   4.45 ml (N = 10), while the intake by SL-DRN was always lower than 2.45   0.86 ml (N = 10, P < 0.00001). Sodium- and water-depleted L-DRN rats also exhibited an increased sodium appetite (13.9   2.0 ml, N = 11) compared to SL-DRN (4.6   0.64 ml, N = 11) after 120 min of observation (P < 0.02). The sodium preference of L-DRN rats in both conditions was always higher than that of SL-DRN rats. These results suggest that electrolytic lesion of the DRN overcomes a tonic inhibitory component of sodium appetite.
authors.affiliation: Departamento de Ciências Fisiológicas, Instituto de Biologia, Universidade Federal Rural do Rio de Janeiro, Seropédica, RJ, Brasil.
authors.forename: E L
authors.initials: EL
authors.lastname: Olivares
authors.forename: R H
authors.initials: RH
authors.lastname: Costa-E-Sousa
authors.forename: H R
authors.initials: HR
authors.lastname: Cavalcante-Lima
authors.forename: H R C
authors.initials: HR
authors.lastname: Lima
authors.forename: P L
authors.initials: PL
authors.lastname: Cedraz-Mercez
authors.forename: L C
authors.initials: LC
authors.lastname: Reis
mesh_terms: D000818:Animals; D001066:Appetite / Q000502:physiology*; D004326:Drinking / Q000502:physiology*; D004556:Electric Injuries / Q000503:physiopathology; D008297:Male; D011903:Raphe Nuclei / Q000293:injuries*; D051381:Rats; D017208:Rats, Wistar; D012965:Sodium Chloride / Q000008:administration & dosage*; D013997:Time Factors
chemical_list: D012965:Sodium Chloride