“Functional interelationship between the lateral parabrachial nucleus (LPBN) and brain areas involved in sodium balance regulation”.

GODINO, A; L. MARGATHO; J. ANTUNES-RODRIGUES; L. VIVAS

Aguas de Lindoia-Sao Pablo, Brasil.

Congreso; Reunión Anual de la Federación de Sociedades de Biología Experimental- FeSBE; 2005

OBJECTIVES: The goal of the present work was to study the monosynaptic connections between the groups of cells activated after salt-induced ingestion and the LPBN neurons. METHODS AND RESULTS: In Wistar male rats (250-300gr), to identify the activated neurons projecting to the LPBN we used the analysis of central Fos immunoreactivity following peritoneal dialysis-induced sodium intake in combination with the immunodetection of the retrograde tracer, Fluorogold. (FG). FG was administered into the LPBN through an iontophoretic injection. After 7 days, the sodium appetite was stimulated by an acute body sodium depletion induced by peritoneal dialysis (PD). Twenty-four hours after PD (n=4) and PD-sham (n=2), an intake test of 2% NaCl solution was given. Ninety minutes after the intake test, the animals were perfused for immunohistochemical detection of Fos and FG. Data are reported as means ±SEM. The level of significance was set at p<0.05. Compared to PD-sham group our data showed that: Along the brainstem the number of double immunoreactive cells significantly increased in PD rats within the nucleus of the solitary tract (PD:4.7±0.7 vs PD-Sham:0±0) and the dorsal raphe nucleus (PD:6±0.6 vs PD-Sham:2.5±0.5). At forebrain level, the Fos-FG positive cells were significantly augmented in the ventral and posterior subnuclei of the hypothalamic paraventricular nucleus (PD:6±0.7 vs PD-Sham:1.5±0.5) and in the Central Extended Amygdala complex, specifically the laterodorsal division of the bed nucleus of the stria terminalis (PD:4.3±0.3 vs PD-Sham:1±0.9) and the lateral division of the central amygdaloid nucleus (PD:5.3±1 vs PD-Sham:0.5±0.5). Besides, the subfornical organ (PD:3.6±0.3 vs PD-Sham:0±0) and organum vasculosum of the laminae terminalis (PD:2.3±0.3 vs PD-Sham:0±0), showed a higher number of double immunoreactive cells in the PD rats. CONCLUSION: The present results reveal the specific neuronal nuclei, along the brainstem and forebrain levels, activated by sodium consumption projecting to the LPBN. These pathways may form a central neural circuit that receives and integrates input derived from body fluid control systems. FAPESP, CNPq, CONICET and ANPCyT