Chapter 9: Neurochemical Circuits Subserving Fluid Balance and Baroreflex: A Role for Serotonin, Oxytocin, and Gonadal Steroids.

VIVAS L; GODINO A; DALMASSO C; CAEIRO XE; MACCHIONE AF; CAMBIASSO MJ

Neurobiology of Body Fluids Homeostasis: Transduction and Integration

Taylor & Francis Group

Año: 2014; p. 141 - 157

Changes in body water/sodium balance are tightly controlled by the central nervous system (CNS) to avoid an abnormal cardiovascular function and develop of pathological states. This process of sensory integration takes place in different nuclei, with diverse phenotype and at different levels of the CNS. The aim of our work was to study the specific neurochemical groups, their roles, their connections and the associated endocrine responses during body sodium depletion or sodium overload conditions. For this purpose we combined the immunohistochemical detection of different neurotransmitters or their receptors, a retrograde transported dye and a marker of neural activity. We have also analyzed the firing frequency changes employing in vivo single-unit extracellular recording. Our main results demonstrated that in body sodium depletion states the serotonergic cells of the dorsal raphe nucleus (DRN) are activated after body sodium status was reestablished, independently of the concentration of the NaCl consumed, suggesting that this system is involved in the inhibition of sodium appetite under conditions of satiety. In contrast, the paraventricular and supraoptic oxitocinergic neurons were activated, and the oxytocin plasma levels increased only after hypertonic NaCl intake, in both depleted and nondepleted animals, suggesting that this system is involved in the processing of hyperosmotic signals. Our hodological results provide insight into how the different neurochemical groups form a neural network that regulates body fluid balance showing the main integratory nuclei involved in the satiety phase of sodium appetite. The electrophysiological experiments may allows us to confirm in an ?in vivo? model, that the DRN serotonergic neurons increases their firing frequency during an increase in systemic sodium concentration and osmolality, possibly to modulate sodium and water intake/excretion and avoid an extracellular volume expansion. Finally, we will also discuss our recent evidence supporting the hypothesis that Ang II-mediated acute blunting of baroreflex regulation of heart rate is under the control of XY/XX sex chromosome complement regardless of the gonadal status of the animals.