“Connectional between the lateral parabrachial nucleus and other neuronal population groups involved in blood volume expansion response”

LISANDRA O. MARGATHO; L. VIVAS; A. GODINO; LUCILA LK. ELIAS; J. ANTUNES-RODRIGUES

San Diego, California.

Congreso; 87 th Anual Meeting of the Endocrine Society; 2005

CONNECTIONS BETWEEN THE LATERAL PARABRACHIAL NUCLEUS AND OTHER NEURONAL POPULATION GROUPS INVOLVED IN THE BLOOD VOLUME EXPANSION (BVE) RESPONSE. Lisandra O Margatho 1*, Laura M Vivas 2, Andrea Godino 2, Lucila LK Elias 1 and Jose Antunes-Rodrigues 1. 1 Department of Physiology, School of Medicine of Ribeirao Preto - USP, Ribeirao Preto, Sao Paulo, Brazil, 14049 900 and 2 Instituto de Investigacion Medica Mercedes y Martin Ferreyra, Cordoba, Cordoba, Argentina. Our previous evidences showed an increase in oxytocin (OT) and atrial natriuretic peptide (ANP) secretion after isotonic blood volume expansion (BVE) while vasopressin (AVP) secretion is inhibited. We have also demonstrated that injection of methysergide (MET), a serotoninergic antagonist, into the lateral parabrachial nucleus (LPBN) reduces electrolyte excretion and urine output induced by BVE. Taken together, these results suggest that the serotoninergic system participates in the hydroelectrolyte response after BVE, modulating the activity of OT and AVP neurons. The purpose of the present study was to identify the direct or monosynaptic connections between the neuronal groups activated after BVE and the LPBN neurons. Male Wistar rats (250-300 g) were injected with Fluorogold (Chemicon International) dissolved as a 2% solution in isotonic saline (0.15M NaCl). Bilateral iontophoretic injections of Fluorogold into the LPBN were made over a 90 second period. Seven days after the iontophoretic injection of the retrograde neuronal tracer in the LPBN, a catheter was inserted into the right external jugular vein and advanced to the right atrium. Acute blood volume expansion was performed by injection of isotonic saline (0.15 M NaCl, 2 ml/100 g b.w.) over 1 min. We analyzed the double-labeled (Fos-FG)ir within different nuclei of the brain which send projections to the LPBN. The results showed that after isotonic BVE the LPBN receive direct and relayed projections and double-labeled (Fos-FG)ir from the dorsal raphe nucleus (high density), central amygdala (high density), paraventricular nucleus (medium density), solitary tract nuclei (medium density), bed nucleus of the stria terminalis (low activation) and locus coeruleus (low activation). Taking into account our previous evidences about the role of hypothalamic areas in the control of body fluid homeostasis, the present morphofunctional findings reveal the specific neuronal pools within these brain nuclei activated by an acute blood volume expansion projecting to the LPBN and that may form a central neural circuit that receive and integrate inputs derived from body fluid control systems.Financial Support: FAPESP, PRONEX, CNPq and CONICET. A continuación se adjunta el abstract ya que no se dispone versión de Power Point.