Dorsal raphe nucleus lesion modulates sodium appetite

C. PORCARI; B. BAEZ; L. VIVAS; A. GODINO

Huerta Grande, Córdoba

Congreso; Congreso Anual de la SAN (Sociedad Argentina de Neurociencia); 2014

Sociedad Argentina de Neurociencia

Previous studies from our laboratory have shown that acute Na depletion (SD) by peritoneal dialysis produces a rapid and significant drop in serum and CSF Na concentration within 1-4 hours later; however sodium appetite (SA) became evident just 20 hours later when the extracellular sodium levels has been recovered maybe thanks to body sodium reservoirs from bone or liver. To explain the long delay between the SD and SA after the onset of hypovolemia/hyponatremia, our hypothesis proposes that the stimulatory effects of angiotensin II on sodium appetite normally involve interactions with tonic inhibitory brain serotonin (5-HT) circuits, particularly 5HT neurons of the dorsal raphe nucleus (DRN), which should be inhibited in order to release SA. The aim of this work was to analyze the DRN participation in the temporal dissociation between SD and the appearance of SA behavior, particularly, 2h after SD when the rats are hypovolemic/hyponatremic but SA is not evident. In adult male Wistar rats we investigated the effects of DRN transitory lesion induced by 2% lidocaine injection on hypertonic-NaCl intake 2h after SD stimulated by Furosemide combined with low-sodium diet. DRN lesion (0.5 ìl site) increased NaCl intake, 2 h after SD in comparison with sham-lesioned rats (p=0.005; DRN-lesion=0.6ml/100 bw vs DRN-sham lesion= 0ml). In summary, these results show that DRN modulates sodium intake during the delay of SA appearance, being in part responsible for the temporal dissociation between SD and the behavioral arousal.