Dorsal raphe nuclei integrate allostatic information evoked by depletion-induced sodium ingestion

BADAUE-PASSOS, D. JR.; GODINO, A.; JOHNSON, A.K.; VIVAS, L.; ANTUNES-RODRIGUES, J

EXPERIMENTAL NEUROLOGY

Academic Press, Inc. Elsevier Science

Lugar: New York; Año: 2007 vol. 206 p. 86 - 94

0014-4886

Structures of the lamina terminalis (LT) sense and integrate information reflecting the state of body water and sodium content. Output from the LTprojects into a neural network that regulates body fluid balance. Serotonin (5-HT) and the dorsal raphe nuclei (DRN) have been implicated in theinhibitory control of salt intake (i.e., sodiumappetite). Signals arriving fromthe LTevoked by fluid depletion-induced sodiumingestion interact withthisinhibitory serotonergic system. We investigated the role of neurons along the LT that directly project to the DRN. We analyzed the pattern ofimmunoreactivity (ir) of LT cells double-labeled for Fos (a marker of neural activity) and Fluorogold (FG; a retrograde tracer) following sodiumdepletion-induced sodium intake. Seven days after injection of FG into the DRN, sodium appetite was induced by furosemide injection and overnightaccess to only a low sodium diet (Furo-LSD) and distilled water. Twenty-four hours later, access to 0.3MNaCl was given to depleted or sham-depletedrats and sodium intake was measured over the following 60 min. Ninety minutes after the termination of the intake test, the animals were perfused andtheir brains were processed for immunohistochemical detection of Fos and FG. Compared to sham-depleted animals there was a significantly greaternumber of Fos-/FG-ir double-labeled cells in the subfornical organ, the organumvasculosumof the lamina terminalis and the median preoptic nucleus inrats that ingested NaCl. Projections from the LTcells may contribute to inhibitorymechanisms involving 5-HT neurons in the DRN that limit the intakeof sodium and prevent excess volume expansion.