The Role Of Brain Angiotensinergic AT₁ Receptor In The Carbachol-induced Natriuresis And Expression Of NNOS In The Locus Coeruleus (LC) And Proximal Convoluted Tubule (PCT)

Objective: In the present study, we investigated the correlation between the natriuresis and the changes of nNOS-immunoreactivity (nNOS-IR) in the locus coeruleus (LC), proximal convoluted tubule (PCT) following intracerebroventricular (ICV) injection of cholinergic stimuli carbachol in rats.Methods: Male SD rats were randomly divided into four groups: NS+CBC group, Los+CBC group, Los+NS group and NS+NS group. The natriuresis and the changes of nNOS-IR in LC, PCT were observed by experiment in vivo and immunohistochemistry. Meanwhile, the effect of blocking AT₁ receptor with losartan was also observed.Results: 40 min after ICV injection of carbachol (0.5μg), urinary sodium excretion was significantly increased to (0.548±0.049)μmol/min·100g^-1(P﹤0.05). Immunohistochemistry showed that carbachol induced an increase of nNOS-IR in LC and renal proximal tubular cells(P﹤0.05). After pretreatment with losartan 20μg, urinary sodium excretion was reduced to (0.249±0.067)μmol/min·100g^-1(P﹤0.05), and nNOS-IR in LC, PCT induced by carbachol were also reduced(P﹤0.05).Conclusion: Our results indicated that ICV cholinergic stimulation could induce the natriuresis and increase the activity of nNOS in LC and PCT. The blockade of AT₁ receptor might inhibit the effects in LC and PCT induced by carbachol. Consequently, we provided new evidence that brain angiotensinergic pathway and brain NO-dependent neural pathway contributed to renal changes in the natriuresis to brain cholinergic stimuli...