Neurobiorheology. A new branch of biorheology. Historical background and current ideas.

The application of principles of biorheology, hemorheology and perihemorheology on problems of the nervous system in health and disease was suggested by Alfred L. Copley (1982, 1987). Late in 1988 Copley and Sourander considered neurobiorheology to be an appropriate term for a new branch of biorheology bridging the gap between biorheology and neurobiology. Neurobiorheology can be defined as a research field concerned with deformation behaviour of matter including flow and transportation in context with the structure and function of the nervous system at macroscopic, cellular, subcellular and molecular levels. It may be considered a basic life science with important clinical applications. Its "raison d'être" should be to apply various ways of thinking, calculations and techniques used in biorheology to treat and if possible to solve neurobiological problems. Many regionally different chemical, structural and functional properties characterize the developing and adult nervous system and those parts of the circulatory system ("vessel-blood organ") which penetrate the nervous system at all levels. Considering the close metabolic and functional relations between neurons and surrounding non-neuronal ectodermal cells, neuroglial and Schwann cells deriving from common precursor cells in the wall of the neural tube and neural crest respectively, the term neuroectodermal organ appears suitable. The almost parallel ontogenetic evolution of vessel-blood organ and neuroectodermal organ and their interaction during the entire individual life cycle constitutes a challenging stimulus for integrated research. The main purpose of this review is to give some examples of importance concerning still insufficiently elucidated neurobiological problems suitable for biorheological approaches. Particular attention will be paid to the microenvironment at central and peripheral levels of the neuroectodermal organ.