DORSAL RAPHE NUCLEUS INVOLVEMENT IN SODIUM APPETITE DELAY

A. GODINO; C. PORCARI; L. VIVAS

Congreso; 1 Panamerican congress of physiological Sciences; 2014

DORSAL RAPHE NUCLEUS INVOLMENT IN SODIUM APPETITE DELAY Previous studies from our laboratory have shown that acute Na depletion (SD) by peritoneal dialysis (PD)produces a rapid and significant drop in serum and CSF Na concentration within 1-4 hours after PD; 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 proposed that the stimulatory effects of angitoensin II on sodium appetite normally involves interactions with inhibitory serotonergic (5-HT) brain circuits, mainly 5HT neurons of the dorsal raphe nucleus (DRN), and that system have to be inhibit to release SA. The aim of the present work was to analyze the participation of DRN in the temporal dissociation between sodium depletion (SD) and the appearance of SA behavior, particularly, 2h after SD when the rats are hypovolemic/natremic but SA is not evident. We investigated the effects of transitory lesion of DRN induced by lidocaine 2% on hypertonic NaCl at 2h after SD (induced by Furosemide combined with low sodium diet) in Wistar male rats. DRN lesions (0.5 μl site) increased hypertonic NaCl intake when tested 2 h after SD in compared with sham DRN lesion rats (p=0.005; DRN-lesion=2.25ml vs DRN-sham lesion= 0ml). In summary, these results show that DRN modulate sodium intake during the delay of sodium appetite, and it is in part responsible for the temporal dissociation between sodium depletion and the behavioral arousal.