RESUMO
<p><b>AIM AND METHODS</b>To investigate the role of modulation by angiotensin AT1 receptor in sodium and water excretion induced by cholinergic agonist carbachol. Tyrosine hydroxylase immunoreactivity (TH-IR) in hypothalamus were also observed.</p><p><b>RESULTS</b>The natriuretic and diuretic effect induced by carbachol (CBC) were partially inhibited by pretreatment of losartan, a specific blocker of angiotensin AT1 receptor (P < 0.05). Immunohistochemistry showed that both TH-IR density and number of TH-IR positive neurons were markedly increased in PaPo, Arc, Pe and AHP of hypothalamus at 40 min after carbachol administration, as compared with NS group (P < 0.05). However, in losartan pretreated group, the number and the density of TH-IR were significantly decreased in such nuclei mentioned above except PaPo.</p><p><b>CONCLUSION</b>The results above suggest that brain AT1 receptor appears to be involved in mediating natriuresis induced by cholinergic stimulus. The blockade of AT1 receptor may down regulate the excitability of adrenergic neurons in Arc, Pe and AHP induced by CBC. We postulate that brain adrenergic and angiotensinergic pathway get involved in natriuresis induced by brain cholinergic stimulus together. Moreover, angiotensinergic neurons may influence the activity of adrenergic neurons in hypothalamus.</p>