title: Inhibition of natriuresis in median eminence polydipsia: effects after intake of diets with different osmolalities and after hypertonic NaCl administration.
abstract: Lesions in the hypothalamic median eminence (ME) induce polydipsia and polyuria in male rats. A first experiment was designed to examine the effect of salt consumption (standard 0.25 percent Na+ vs. low-salt 0.04 percent Na+ diet) on the fluid-electrolytic balance (plasma sodium, urinary sodium excretion, urine osmolality) and water intake of ME polydipsic animals. In the first 6 h post-surgery, the natriuretic response was higher in ME-lesioned animals than in control groups. At 24 h post-surgery, however, less sodium was excreted by ME rats fed with a standard salt diet (ME/SS), despite showing no decrease in salt intake, and they evidenced an increase in plasma sodium concentration and water intake. Urine osmolality was significantly higher in control animals than in either ME-lesioned group. In experiment 2, hypertonic NaCl administration (2 ml/2M) increased the polydipsic behavior of ME-lesioned but not control rats (day 2). Animals deprived of food/salt showed a significant reduction (on day 2) in the initial (day 1) polydipsia, which increased on day 3 when the animals had access to a standard-salt diet. These results suggest that the reduced natriuretic response and the consequent sodium retention observed in ME animals may exacerbate the hydromineral imbalance of this polydipsic syndrome.
authors.affiliation: Department of Psychobiology, University of Granada, Granada, Spain, jmahia@ugr.es.
authors.forename: Javier
authors.initials: J
authors.lastname: Mahía
authors.forename: Antonio
authors.initials: A
authors.lastname: Bernal
authors.forename: Amadeo
authors.initials: A
authors.lastname: Puerto
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001930:Brain Injuries / Q000150:complications / Q000473:pathology; D004326:Drinking / Q000187:drug effects / Q000502:physiology; D004435:Eating / Q000187:drug effects / Q000502:physiology; D008297:Male; D008473:Median Eminence / Q000187:drug effects / Q000293:injuries / Q000378:metabolism*; D009994:Osmolar Concentration; D059606:Polydipsia / Q000097:blood / Q000209:etiology / Q000473:pathology* / Q000652:urine; D051381:Rats; D017208:Rats, Wistar; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage*; D012965:Sodium Chloride / Q000378:metabolism*; D012982:Sodium, Dietary / Q000008:administration & dosage* / Q000652:urine; D013997:Time Factors; D014882:Water-Electrolyte Balance / Q000187:drug effects* / Q000502:physiology
chemical_list: D012462:Saline Solution, Hypertonic; D012982:Sodium, Dietary; D012965:Sodium Chloride