Central and peripheral release of vasopressin and oxytocin in the conscious rat after osmotic stimulation.

Vasopressin (AVP) and oxytocin (OXT) were measured by radioimmunoassay in push-pull perfusates and tissue samples of various brain areas, plasma and cerebrospinal fluid (CSF) of male rats in response to osmotic stimulation. Hypertonic saline caused a significant rise in plasma AVP and OXT and different changes in peptide contents, in the septum and hippocampus at 30 and 60 min after intraperitoneal injection. Push-pull perfusion (20 microliters artificial CSF/min, 30-min periods) of the septum and dorsal hippocampus of conscious, unrestrained animals revealed a significant, stimulus-evoked release of both AVP and OXT. This release was: (1) not always reflected by corresponding changes in the regional peptide content; (2) simultaneous with the peripheral release from the posterior pituitary; and (3) probably the result of synaptic/parasynaptic events as suggested by use of agents in the artificial CSF which either inhibit or facilitate the release from intact fibre terminals.