The interrelationship between cholinergic pathway in the magnocellular paraventricular nucleus and natriuresis.

The central nervous system is known to play important roles in the regulation of renal sodium excretion. The present study was designed to reveal the interrelationship between cholinergic pathway in the magnocellular paraventricular nucleus (PVN) and the natriuresis induced by brain cholinergic stimuli. The results indicated that urinary sodium excretion was significantly increased at 40 min after intracerebroventricular (ICV) injection of carbachol (CBC). Immunohistochemical studies showed that CBC increased choline acetyltransferase-immunoreactivity (ChAT-IR) in the magnocellular PVN and renal proximal convoluted tubule (PCT), respectively. After pretreatment with atropine, urinary sodium excretion was significantly reduced, and carbachol-increased ChAT-IR in the magnocellular PVN and PCT was also significantly decreased. These results suggested that brain cholinergic stimuli induced the natriuresis and increased the activity of cholinergic neurons in the magnocellular PVN and cholinergic system in the PCT. The blockade of muscarinic receptor completely abolished the natriuresis and partially inhibited carbachol-exerted stimulatory effects in the magnocellular PVN and PCT. To summarize, brain cholinergic pathway and peripheral cholinergic system in kidney were found to contribute to the natriuresis following brain cholinergic stimulation. Our findings revealed novel evidence that PVN was involved in the natriuresis via humoral mechanisms.