Effect of AT₁ receptor on changes of tyrosine hydroxylase-immunoreactivity in rostral ventrolateral medulla induced by brain cholinergic stimuli in rats / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the effect of AT₁ receptor on the changes of tyrosine hydroxylase-immunoreactivity (TH-IR) in rostral ventrolateral medulla (RVLM) induced by brain cholinergic stimuli in rats.</p><p><b>METHODS</b>Male SD rats were randomly divided into 4 groups: NS + CBC group, Los + CBC group, Los + NS group and NS + NS group. AT₁ was blocked by pretreatment of 20 μg losartan in Los + CBC and Los + NS groups; intracerebroventricular injection of 0.5 μg carbachol was used for cholinergic stimuli in NS + CBC and Los + CBC groups; normal saline (NS) was used for control. The output amount of natrium in kidney, glomerular filtration rate (GFR) and renal plasma flow (PRF) were observed. The changes of TH-IR in the RVLM were observed by immunohistochemistry.</p><p><b>RESULT</b>In NS + CBC group carbachol induced potent natriuresis, after pretreatment of losartan the natriuretic effect was partially inhibited in Los + CBC group. Both the number and optical density of TH-IR positive neurons in NS + CBC group were markedly increased than those in NS + NS group (P < 0.05); while those in Los + CBC group were significantly lower than those in NS+CBC group (P < 0.05). Intracerebroventricular injection of carbachol and losartan had no effect on GFR and RPF(P > 0.05).</p><p><b>CONCLUSION</b>The results suggest that cholinergic stimuli can induce potent natriuresis and increase the activity of adrenergic neurons in the RVLM; the above effects can be down regulated by blockade of brain AT₁ receptor.</p>

The role of AT1 receptor in the changes in TH immunoreactivity of LC induced by brain cholinergic stimulation / 中国应用生理学杂志

<p><b>AIM AND METHODS</b>In the present study, we investigated the TH immunoreactivity and the expression of angiotensin AT1 receptor in locus coeruleus after intracerebroventricular (i. c. v.) injection of carbachol in conscious SD rats with immunohistochemistry. Meanwhile the effects of blocking AT1 receptor were also observed.</p><p><b>RESULTS</b>Both mean optical density and number of TH and AT1 immunoreactive positive neurons were markedly increased in locus coeruleus after 40 minutes of i.c.v. injection of carbachol (0.5 microg). The enhancement was significantly reduced by i. c. v. injection of losartan.</p><p><b>CONCLUSION</b>The results above suggest that i. c. v. injection of cholinergic agonist carbachol can enhance the activity of adrenergic neurons and the expression of AT1 receptor in locus coeruleus. The blockade of AT1 receptor may down regulate the above action induced by carbachol in locus coeruleus.</p>