ABSTRACT
The term catecholamines is derived from their structure, which incorporates an amine side chain and a catechol ring. The catecholamine family is composed of dopamine (DA), norepinephrine (NE) and epinephrine (Epi). Although they differ only in a hydroxyl and a methyl group, respectively, the three catecholamine neurons have a dissimilar distribution within the brain, activate different sets of receptors, and exert distinct functions. The anatomy and physiology of the three catecholaminergic neurons in the brain are first described, with an emphasis on the dopaminergic neurons. In addition to regulating important neurological functions such as locomotion, cognition, and reward, the brain dopaminergic neurons are a critical component of the neuroendocrine functions of the brain. Three dopaminergic pathways, the incerta-hypothalamic (IHDA), tuberoinfundibular (TIDA), and tuberohypophysial (THDA), originate in the hypothalamus, supply DA to most hypothalamic nuclei, and link the nervous system to the endocrine system via the pituitary gland. Within the pituitary gland, only the posterior pituitary (both neural and intermediate lobes) is directly connected to the hypothalamus through a nerve tract, whereas the anterior lobe is not innervated but, rather, receives hypothalamic information through a specialized hypophysial portal vasculature.
