Pharmacology of the cerebral circulation
Kelly PAT., Garland CJ.
© The editors and contributors, 1996. All rights reserved. The precise mechanism by which vascular tone is coupled to regional neuronal metabolism is not known, but it is likely to be multifactorial, reflecting the concerted action of changes in the local ionic composition of the extracellular fluid (K<sup>+</sup>, H<sup>+</sup>, pC0<inf>2</inf>, and pO<inf>2</inf>) and changes in the concentration of chemical transmitters and neuromodulators released from the neurones of the brain. Superimposed upon these controlling processes is the influence of perivascular nerves, which appears to predominate in larger cerebral arteries, factors released from intimal endothelial cells, and the passive myogenic properties of cerebrovascular smooth muscle cells. The complex nature of the link between cerebral blood flow and metabolism, and the possible mediation of neurotransmitters, necessitates in vitro pharmacological studies, where the kinetics of agonist/receptor interactions can be examined under controlled, steady state conditions.