Received March 18, 2008
Revised April 17, 2008
Accepted after revision April 23, 2008
Neuroendocrinology/Endocrinology [270]
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Oestrogenic influence on brain AT1 receptor signalling on the thirst and salt appetite in osmotically-stimulated and sodium-depleted female rats
André S Mecawi 1,
Ailin Lepletier 1,
Fabricia V Fonseca 1,
Iracema G Araujo 1,
Luís C Reis 1*
1 Federal Rural University of Rio de Janeiro
* To whom correspondence should be addressed. E-mail: lcreis{at}ufrrj.br.
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Abstract |
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The present work was carried out to investigate the role of the angiotensin II AT1 receptors on nocturnal thirst and sodium appetite expression raised by classical paradigms of osmotic and sodium depletion challenges in ovariectomised rats chronically treated with oil or oestradiol benzoate (EB, 20 µg animal-1, daily). In both conditions the animals were given saline or losartan (108 nmol animal-1, I.C.V.), a selective AT1 receptor blocker. EB therapy has significantly reduced the water intake induced by water deprivation, sodium depletion produced by frusemide injected 24 h before, and S.C. acute frusemide plus captopril injection (FUROCAP protocol) with no alteration following S.C. hypertonic saline injection. On the other hand, EB therapy decreased the salt intake induced by sodium depletion and FUROCAP protocols with no alteration following water deprivation and S.C. hypertonic saline injection. Central AT1 blockade inhibited the dipsogenic response induced by water deprivation, osmotic stimulation, chronic sodium depletion and FUROCAP protocols and further inhibited the natriorexigenic response induced by sodium depletion in ovariectomised rats. EB therapy significantly attenuated the losartan antidipsogenic and antinatriorexigenic actions following sodium depletion and FUROCAP protocols. Current outcomes indicate that ovariectomised rats express increased AT1 receptor signalling related to thirst and sodium appetite responses. Oestrogen therapy and brain angiotensin II AT1 receptor blockade weakened or markedly decreased the behavioural responses during the nocturnal period, a time at which brain angiotensinergic activity is expected to be more prominent. Finally, we demonstrated through different experimental paradigms a clear-cut influence of oestrogenic status on behavioural AT1-induced signalling response.
Key Words:
Angiotensin, Fluid balance, Oestrogen
