AJP - Endocrinology and Metabolism, Vol 248, Issue 3 346-E352, Copyright © 1985 by American Physiological Society
CSF vasopressin rhythm is effectively insulated from osmotic regulation of plasma vasopressin
R. J. Coleman and S. M. Reppert
By using our method for continuous removal of cisternal cerebrospinal fluid
(CSF) and intermittent sampling of blood from unanesthetized freely moving
cats, we investigated the effect of osmotic-induced changes in plasma
vasopressin on the daily rhythm of CSF vasopressin. Examination of the
daily profiles of vasopressin and osmolality in the CSF and plasma of six
euhydrated animals showed that CSF vasopressin concentrations exhibit a
clear daily rhythm, whereas CSF osmolality and plasma vasopressin and
osmolality do not exhibit such daily variation. A 48-h period of water
deprivation caused marked sustained elevations in plasma vasopressin
concentrations, which returned to basal levels on rehydration. In contrast,
water deprivation had only a small effect on the CSF vasopressin rhythm.
Although there was a significant elevation of the normally low nighttime
CSF vasopressin levels during water deprivation in three of the four
animals studied, high daytime vasopressin levels were unaltered and the
daily rhythm was clearly evident before, during, and after the period of
water removal in all animals. Changes between plasma vasopressin and
osmolality were significantly correlated in all animals. Changes between
plasma and CSF osmolality were significantly correlated in three of the
four animals. The data indicate that the circadian regulation of the CSF
vasopressin rhythm is effectively insulated from the osmotic regulation of
plasma vasopressin.
