title: Participation of the median raphe nucleus and central serotoninergic pathways in the control of water electrolyte excretion.
abstract: 1. The role of the median raphe nucleus (MRN) and of increased central serotonin (5HT) synthesis/release in the mediation of Na+ excretion (UNaV) and K+ excretion (UKV) and of urine output (UV) was evaluated for 120 min. 2. Male Wistar rats weighing 220-280 g were used in each group of 12-13 animals. The rats implanted with a cannula in the MRN were injected with saline (0.5 microliters) or with 5.0 and 15.0 ng/0.5 microliters kainic acid (KA), an excitatory amino acid (EAA). Another group of rats was injected ip with 200 mg/kg saline or tryptophan, the initial precursor of 5HT synthesis. 3. Injection of both kainic acid and tryptophan led to increased Na+ excretion, but the magnitude and time course were different for each treatment. 4. Both KA doses were effective in increasing UNaV (0.61 +/- 0.08, mean +/- SEM, and 0.95 +/- 0.19 microEq/min, respectively, vs 0.27 +/- 0.04 microEq/min for saline at 60 min). The effect on UKV was statistically significant with the 15.0 ng dose (0.44 +/- 0.05 microEq/min vs 0.25 +/- 0.03 microEq/min for saline) at 20 min. 5. Tryptophan administration caused an initial gradual increase in UNaV which became steady and significant after 60 min (1.02 +/- 0.15 microEq/min vs 0.36 +/- 0.06 microEq/min for saline), as well as an increase in UKV (0.58 +/- 0.06 microEq/min vs 0.26 +/- 0.04 microEq/min for saline) at 60 min and throughout the remainder of the observation period. 6. KA-induced MRN stimulation and systemic tryptophan overload significantly increased UV at 60, 80 and 100 min (30 to 97% above control values).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Brasil.
authors.forename: L C
authors.initials: LC
authors.lastname: Reis
authors.forename: M J
authors.initials: MJ
authors.lastname: Ramalho
authors.forename: J
authors.initials: J
authors.lastname: Antunes-Rodrigues
mesh_terms: D000818:Animals; D007608:Kainic Acid / Q000494:pharmacology*; D008297:Male; D011188:Potassium / Q000378:metabolism*; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism / Q000494:pharmacology*; D014556:Urine; D014882:Water-Electrolyte Balance / Q000187:drug effects*
chemical_list: D011985:Receptors, Serotonin; D014364:Tryptophan; D012964:Sodium; D011188:Potassium; D007608:Kainic Acid