Efeitos crônicos do aumento da liberação de serotonina, da inibição da recaptação pré-sináptica de serotonina e da estimulação de receptor 5-HT1A, na sede e no apetite por sódio em ratos

Abstract

In order to investigate the hypothesis of the influence of serotonergic system on the control of dipsogenic and sodium appetite, we examined the effects of chronicallytreated rats with the brain serotonin releaser, fenfluramine, the 5-HT1A agonist, 8-OHDPAT and the selective serotonin re-uptake inhibitor, sertraline. Animals treated with 5- HT1A agonist and brain serotonin releaser were sodium depleted and then their fluids intake analyzed. The first group decreased significantly the salt intake response while the second group intensified the sodium appetite 2 weeks after the first administration of fenfluramine. The water consumption was not altered in none of the groups when compared to their respective controls. Sodium-depleted animals that were treated with sertraline showed a more intense natriorexigenic response. On the other hand, water deprivation induced a lower water intake in SERT-treated rats than the controls. Osmotic simulation evoked a dipsogenic response significantly lower in SERT group. Fluids and food deprivation induced a weak dipsogenic response in SERT treated-rats compared to controls but without difference on saline intake. An increased urinary density and decreased plasma sodium levels in SERT-treated rats correlated with the highest plasma vasopressin and oxytocin levels at the 3rd week post-treatment. The obtained results in chronically-treated rats with the 5-HT1A agonist and the brain serotonin releaser, suggest that the alteration on the brain serotoninergic activity influences the sodium appetite expression, possibly after 5-HT1A autoreceptor desensitization produced by 8-OH-DPAT or brain serotonin depletion achieved with fenfluramine treatment. The results of chronically-treated rats with sertraline, constitute the first evidence of alterations on the threshold for thirst and sodium appetite response in SERT-chronically-treated rats. These alterations possibly are consequence of the hyponatremia provided by inappropriate secretion of AVP and OT.