Submitted on January 11, 2008
Accepted on September 3, 2008
WATER DEPRIVATION INCREASES FOS EXPRESSION IN HYPOTHALAMIC CORTICOTROPIN-RELEASING FACTOR NEURONS INDUCED BY RIGHT ATRIAL DISTENSION IN AWAKE RATS
Mauricio Benedetti1, Rodrigo Rorato2, Margaret Castro3, Benedito H. Machado4, Jose Antunes-Rodrigues2, and Lucila Leico Kagohara Elias5*
1 Department of Internal Medicine, University of Sao Paulo, School of Medicine of Ribeirao Preto, Ribeirao Preto, Sao Paulo, Brazil
2 Department of Physiology, University of Sao Paulo, School of Medicine of Ribeirao Preto, Ribeirao Preto, Sao Paulo, Brazil
3 Department of Internal Medicine, University of Sao Paulo, School of Medicine of Ribeirao Preto, Ribeirao Preto, Sao Paulo, Brazil; Ribeirao Preto, Sao Paulo, Brazil
4 Department of Physiology, University of Sao Paulo, School of Medicine of Ribeirao Preto, Ribeirao Preto, Sao Paulo, Brazil; , Brazil
5 , Brazil; Department of Physiology, University of Sao Paulo, School of Medicine of Ribeirao Preto, Ribeirao Preto, Sao Paulo, Brazil
* To whom correspondence should be addressed. E-mail: llelias{at}fmrp.usp.br.
Atrial mechanoreceptors, sensitive to stretch, contribute to regulate heart rate and intravascular volume. The information from those receptors reaches the nucleus tractus solitarius and then the paraventricular nucleus (PVN), known to have a crucial role on the regulation of cardiovascular function. Neurons in the PVN synthesize corticotropin-releasing factor (CRF), vasopressin (AVP) and oxytocin (OT). Stimulation of atrial mechanoreceptor was performed in awake rats implanted with a balloon at the junction of the superior vena cava and right atrium. Plasma adrenocorticotrophic hormone (ACTH), AVP and OT concentrations, Fos, CRF, AVP and OT immunolabeling in the PVN were determined after balloon inflation in hydrated and water-deprived rats. The distension of the balloon increased the plasma ACTH concentrations, which were higher in water-deprived than in hydrated rats (p<0.05). In addition, the distension in the water-deprived group decreased plasma AVP concentrations (p<0.05), compared to the respective control group. The distension increased the number of Fos and double labeled Fos/CRF neurons in the parvocellular PVN, which was higher in the water-deprived than in the hydrated group (p<0.01). There was no difference in the Fos expression in magnocellular PVN neurons after distension in hydrated and water-deprived groups, compared to respective controls. In conclusion, parvocellular CRF neurons showed an increase of Fos expression induced by stimulation of right atrial mechanoreceptors, suggesting that CRF participates in the cardiovascular reflex adjustments elicited by volume loading. Activation of CRF neuron in the PVN by cardiovascular reflex is affected by osmotic stimulation.
