Cerebrospinal fluid vasopressin and oxytocin: evidence for an osmotic response.

A push-pull perfusion technique was used to sample third ventricular cerebrospinal fluid (CSF) in the conscious rat. Ventricular perfusate contained significant quantities of vasopressin and oxytocin, 13.1 and 4.5 pg/ml, respectively. Vasopressin and oxytocin levels were stable over a 3 h perfusion period. High sodium artificial CSF elicited a 4-5-fold stimulation of perfusate concentrations of both peptides. These findings suggest that the CSF represents a dynamic compartment in terms of neuroendocrine function.