Catecholamines and Their Receptors

This chapter provides an overview of catecholamines and their receptors, and possible catecholaminergic mechanisms by which central structures can contribute to the regulation of the cerebral circulation. The possibility of catecholamine-induced changes in the cerebral circulation was first addressed concomitant with the role of perivascular sympathetic innervation. However, there is multiplicity of catecholaminergic neurotransmitters, their various origins, and mechanisms of action. This chapter also discusses dopamine that is primarily located in three midbrain nuclei. These nuclei give rise to two major dopaminergic systems: first, the mesocortical pathway that arises from the substantia nigra and densely innervates the striatum and additionally sends axons to the frontal cortex; second, the mesolimbic pathway which arises from the ventral tegmental area and innervates both cortical and subcortical structures that comprise the limbic system. These systems are principally involved in extrapyramidal motor control; furthermore, their dysfunction underlies various human pathologies such as Parkinson's disease as well as certain aspects of schizophrenia and drug abuse. The chapter describes the general anatomical and functional data of the central catecholaminergic systems, and discusses circulating catecholamines and activation of the reticular formation.