FLUID BALANCE AND BAROREFLEX RESPONSE: NEUROMODULATORS, NEURAL CIRCUITS AND SEX CHROMOSOME COMPLEMENT INFLUENCES

GODINO A; CAEIRO XE; CAMBIASSO MJ; VIVAS L

Revista de Farmacología de Chile

Sociedad de Farmacología de Chile

Año: 2015

0718-8811

ABSTRACT --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Changes in body water/sodium balance are tightly controlled by the CNS to avoid abnormal cardiovascular function and the development of pathological states. This process of sensory integration takes place in different nuclei, with diverse phenotypes and at different levels of the CNS. Our aim 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, a retrograde transported dye and a marker of neural activity. We also determined the involvement of sex chromosome complement (SCC) in both bradycardic baroreflex response and in brain activity in a sodium depletion model. Our results demonstrated that the activity of serotonergic and oxytocinergic neurons significantly increases during blood volume expansion, suggesting their involvement in the homeostatic regulatory response. We also observed tonic activity of serotonergic neurons of the dorsal raphe nucleus (DRN) during the first hours after sodium depletion. The activity then decreased 24 h after sodium depletion and increased after body sodium reestablishment, independently of the sodium concentration of the solution consumed, suggesting that this system is involved in the inhibition of sodium appetite under conditions of satiety. In contrast, the paraventricular and supraoptic oxytocinergic neurons were activated and the oxytocin plasma levels increased only after hypertonic NaCl intake in both depleted and non-depleted animals, suggesting that this system is involved in the processing of hyperosmotic signals. Our hodological results provide insight into how different areas, such as the DRN and lateral parabrachial nucleus, form a neural network that regulates body fluid balance, and show the main integratory nuclei involved in the satiety phase of sodium appetite and consequently in the regulation of extracellular volume. Finally, we also demonstrated that the SCC influences bradycardic baroreflex response and modulates brain activity in nuclei closely involved in the regulatory response to RAAS stimulation. Keywords: Water and electrolyte homeostasis, bradycardic baroreflex response, RAAS, serotonin, oxytocin, sex chromosome complement Rev. Farmacol. Chile (2015) 8(3) 35-51 Received 15-10-2015; Revised 15-11-2015; Accepted 25-11-2015