The Journal of endocrinology
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The passage of 125I-labelled arginine-vasopressin (AVP) and its analogues desmopressin (DDAVP) and desglycinamide arginine-vasopressin (DGAVP) into cerebrospinal fluid (CSF) has been studied in the dog. After intravenous injection or infusion of these peptides radioactive substances were found in the CSF in amounts ranging from 0.5 to 1.4% of the total plasma radioactivity. However, only DDAVP could be identified in the CSF as the unmetabolized peptide. ⋯ Radioactivity was again present in the CSF but no AVP could be identified. These observations showed that the intranasal route of administration provides no increased access to the CSF. The existence of a blood-CSF barrier to AVP is confirmed and indicates that the concentrations of the hormone normally found in CSF arise from sources other than the blood.