Proceedings of The Physiological Society
University of Manchester (2010) Proc Physiol Soc 19, PC218
Hypothalamic oxytocin and vasopressin mRNA expression, plasma oxytocin and vasopressin levels and the mean arterial pressure in rats with chronic ethanol treatment
A. Lopes da Silva1, C. Crestani2, E. Uchoa1, L. Elias1, F. Correa2, L. Resstel2, J. Antunes-Rodrigues1
1. Physiology, University of Sao Paulo, Ribeirao Preto, Sao Paulo, Brazil. 2. Pharmacology, University of Sao Paulo, Ribeirao Preto, Sao Paulo, Brazil.
Ethanol is known as an extremely toxic agent for the central nervous system. Several studies have shown that chronic ethanol intake is associated with autonomic changes and hypertension. This study evaluated plasma vasopressin (AVP) and oxytocin (OT) levels, AVP and OT mRNA in paraventricular nucleus (PVN) and supraoptic nucleus of the hypothalamus (SON), mean arterial pressure (MAP) and heart rate (HR) in response to chronic ethanol treatment. Male Wistar rats (250g) were treated with ethanol for 4 weeks: first week 5%, second week 10% and the last two weeks 20% of ethanol. Blood samples were collected at the end of each ethanol treatment for hormone measurements by specific radioimmunoassay. Hypothalamic nuclei were collected by microdissection, the total RNA was isolated and used for cDNA synthesis, followed by quantitative real-time PCR to determine the relative mRNA expression. During the treatment the animals had a progressive increase of basal values of MAP (F1.34=52.09; P<0.0001) after the first week of treatment, without alteration on HR basal values (F1.39=0.2123; P>0.05). It was observed that the treatment with ethanol increased plasma AVP levels (F1.83=22.97; P<0.0001) without change in plasma OT levels (F1.84=1.929; P>0.05). AVP mRNA expression in the SON (F1.66=66.19; P<0.0001) was increased by the treatment after the second week and AVP mRNA in the PVN (F1.56=26.56; P<0.0001) was increased only after the third week of ethanol treatment. During the treatment no change was observed in OT mRNA in the SON (F1.68=2.109; P>0.05) but an increase in OT mRNA in the PVN (F1.64=0.612; P>0.05) was observed after the fourth week. In summary, these results indicate that ethanol chronic treatment promotes an increase in MAP at first week, but the changes in plasma AVP levels and AVP mRNA expression were seen after the second week. The oxytocinergic system is unlikely to contribute to the autonomic and blood pressure changes induced by chronic ethanol treatment. On the other hand, the increase in MAP was associated with an increase in plasma AVP levels and AVP mRNA in the SON and PVN, suggesting that the vasopressinergic system participates in the maintenance of hypertension induced by prolonged ethanol intake.
Where applicable, experiments conform with Society ethical requirements