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Aims: A neural mechanism regulating aquaporin (AQP) water channels in the kidney was investigated. Methods: Male Sprague-Dawley rats were used. Renal denervation was induced by painting the renal vessels with 10% phenol. The expression of AQP1–4 proteins was determined in the denervated and contralateral kidneys. The expression was also examined in rats which were renally denervated and subjected to water restriction or deoxycorticosterone acetate (DOCA)-salt treatment. Results: Following the unilateral denervation, tissue contents of norepinephrine were significantly decreased in the denervated kidney, while increased in the contralateral kidney. Accordingly, the expression of AQP1–4 proteins was decreased by 15–40% in the denervated kidney, and increased by 30–50% in the contralateral kidney. Immunohistochemistry of AQP2 confirmed its decreases in the denervated kidney and increases in the contralateral kidney. In bilaterally denervated rats, the urine flow increased along with decreased osmolarity. The water restriction increased the expression of AQP channels, however, the magnitude of which was lower in the denervated than in the contralateral kidney. Renal denervation decreased the degree of DOCA-salt hypertension, along with lower expression of AQP channels. Conclusion: It is suggested that the sympathetic nerve should play a specific excitatory role in the regulation of AQP channels in the kidney. Copyright © 2006 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]