Release of Oxytocin into Blood and Cerebrospinal Fluid by Electrical Stimulation of the Hypothalamus or Neural Lobe in the Rat

Abstract

Oxytocin (OT) was measured in blood and cerebrospinal fluid (CSF) samples obtained from anaesthetized rats. Release of OT was evoked by electrical stimulation (15 s) of the hypothalamus or the neural lobe. Stimulation of the neural lobe increased plasma OT sevenfold without altering CSF levels. Hypothalamic stimulation released OT into both blood and CSF, although the rise in CSF was both delayed and prolonged compared to that in plasma. Stimulation sites which released OT into CSF extended over a large medial area of the hypothalamus. More lateral stimulation sites were much less effective. Our results show that the release of OT into blood and CSF can be dissociated and that CSF levels reflect the activity of those hypothalamic OT-neurones which do not project to the neural lobe.