Lack of Increase in Sodium Concentration of Cerebrospinal Fluid in DOCA - SaltHypertensive Rats

The purpose of the present study is to determine whether DOCA-salt treatment could cause an elevation of Na concentration of cerebrospinal fluid (CSF), which may increase blood pressure (BP) as a result of enhanced activity of sympathetic nervous system (SNS) and vasopressin (AVP). Blood pressure was gradually increased by DOCA-salt treatment. Serum NA was also elevated with time by DOCA-salt, and significantly higher in DOCA rats on the 4th treatment week, as compared with controls. By contrast, DOCA-salt did not alter CSF Na at any time of treatment. No relationship was detected between BP and CSF Na at any stage of DOCA-salt hypertension. The precent fall in BP by AVP antagonist or hexamethonium was always greater in DOCA-treated rats than that in the controls. These hypotensive effects were gradually, but consistently enhanced with the development of hypertension in DOCA rats. It is concluded that the enhanced activity of both SNS and AVP system responsible for DOCA-salt hypertension may be attributed to the mechanism(s) unrelated to the increased CSF Na concentration.