Proceedings of a symposium held at Smolenice Castle, Czechoslovakia, June-July 1989, as part of the International Congress of Physiological Sciences. Includes the 27 invited papers by experimental scientists and clinicians whose interest includes the action of circulatory agents on the brain. The unsolicited contributions are published in Endocrinologia Experimentalis 24 (1990). Among the topics are the physiology and neuroendocrine regulation of the blood-brain barrier, possible interactions between circulating factors and anterior pituitary hormone release in neuroendocrine responses to emotional stress, effects of thyroid hormones on the hypothalamic dopaminergic neurons, the role of monokines in the control of anterior pituitary hormone release, and nutritional and hemodynamic factors influencing the adenopituitary function in humans.