According to the classical concept of Geoffrey Harris the pituitary gland is controlled by the brain by means of blood-borne chemical messengers produced by central neurons. The recent isolation and structural characterization of several such messengers by Roger Guillemin and Andrew Schally and their collaborators brought the final proof for this hypothesis. This also meant that the extensive knowledge collected in the field of neurobiology now became highly relevant for the endocrinologists. For this reason it was felt important to organize a symposium which brought together experts in the fields of neurobiology and endocrinology. The idea was to focus the attention on neuronal mechanisms, particularly those related to chemical transmission, which may be of importance for the central regulation of hormonal secretion patterns. We would like to express our sincere gratitude to the Nobel Founda tion for supporting the organization of the Nobel Symposium 42 on "Principles of the Central Regulation of the Endocrine System." We would also like to express our thanks to all participants, to Professor Carl-Gustaf Bernhard, Permanent Secretary of the Royal Academy of Sciences, for making the facilities of the Academ- available to us, and to the Symposium secretaries Mrs. Gun Hultgren, Mrs. Lena Persson and Mrs. Ulla-Britt Wedin. It is a pleasure to acknowledge the generous financial support from the Nobel Foundation and its Nobel Symposium Committee through grants from the Tercentenary Foundation of the Bank of Sweden, and from the Swedish Medical Research Council, KABI AB, Stockholm, and ASTRA AB, Sodertalje."

Volume Transmission Revisited describes the mounting evidence that cells of the central nervous system are able to communicate via a host of chemical signals that flow through the extracellular space. Volume transmission (VT) constitutes a novel and complementary communication system to classical synaptic transmission. The new modality, which does not require specific connections between cells, leads to a reconsideration of the spatial relationships of neurons and glia, brings a new dimension to network modelling and is relevant to both short term interactions and long term tonic states of the brain.

The reader will find 29 chapters describing many of the major discoveries in VT during the last decade.
The most striking feature of this publication is the collecting together of many compelling examples of the ubiquitous nature of VT. These point to its increasing relevance from basic neuroscience research to clinical practice. Those working in other areas will find numerous invaluable examples of how leading investigators have gone about assembling evidence for VT.