NOREPINEPHRINE is found in appreciable amounts in mammalian brain tissue. VOGT (1954) showed that this amine was unequally distributed in various regions of the cat brain, the highest concentrations being found in the hypothalamus. Similar findings were reported for other animal species (BERTLER and ROSENGREN, 1959a; MCGEER, MCGEER and WADA, 1963) and man (SANO, GAMO, KAKIMOTO, TANAGUCHI, TAKE~ADA and NISHINUMA, 1959). Dopamine is also present in the brain in comparable amounts to norepinephrine (MONTAGU, 1957 ; CARLSSON, LINDQVIST, MAGNUSSON and WALDECK, 1958) but with a different regional distribution, the highest concentrations being in the corpus striatum of both animals and man (BERTLER and ROSENGREN, 1959a; SANO et al., 1959; EHRINGER and HORNYKIEWICZ, 1960; BERTLER, 1961). The anatomical distribution of these two catecholamines in the brain was confirmed by the use of fluorescent histochemical techniques which allow a precise description of the cellular localization of the amines in brain tissue (CARLSSON, FALK and HILLARP, 1962; DAHLSTROM and FUXE, 1964; FUXE, 1965). These techniques revealed that norepinephrine and dopamine are specifically localized in complex systems of neurons in the brain, a finding which lends support to the hypothesis that both amines may be neurotransmitters in the central nervous system. The metabolism of catecholamines in the rat brain was studied by introducing small amounts of radioactive norepinephrine or dopamine directly into the lateral ventricle (MILHAUD and GLOWINSKI, 1962, 1963; GLOWINSKI, KOPIN and AXELROD, 1965; GLOWINSKI, IVERSEN and AXELROD, 1966). By this approach the blood-brain barrier to catecholamines can be circumvented, penetration of the radioactive catecholamines into the brain being allowed. The disposition of PHInorepinephrine in the whole brain indicates that [3H]norepinephrine introduced into the lateral ventricle of the brain mixes with the endogenous amine and can be used as a tracer to study the biochemical behaviour of norepinephrine in the brain (GLOWINSKI and AXELROD, 1966). PHIDopamine, which is also taken up and retained in the brain, is rapidly metabolized and converted to norepinephrine (GLOWINSKI et a!., 1966). The unequal regional distribution of the endogeneous catecholamines in the brain led us to undertake a study of the disposition of radioactive norepinephrine and dopamine in various brain regions after intraventricular injection. The regional

Regional studies of catecholamines in the rat brain. I. The disposition of [3H]norepinephrine, [3H]dopamine and [3H]dopa in various regions of the brain.

The ascending monoamine pathways in the rat brain are demonstrated by the pile up of fluorescent material occurring in the axons after various types of lesions. The anatomy of the pathways is outlined in drawings of frontal sections of the brain and the origin and termination of several pathways is determined by studying the anterograde and retrograde degeneration occurring after well localised lesions. It is possible to separate the ascending NA pathways into a dorsal and a ventral bundle of axons. The dorsal bundle innervates the cortex and the hippocampus and the ventral bundle supplies NA nerve terminals to the medulla, the pons, the mesencephalon and the diencephalon. The dorsal bundle is found to originate in the locus coeruleus. Lesions of this nucleus abolish the nerve terminals in all cortical areas and in several other areas of the brain indicating a unique role for the locus coeruleus in influencing the activity of the entire brain. The 5-HT pathways have a distribution similar to the ventral NA pathyway. The course of the nigro-striatal and the meso-limbic DA pathways is presented in detail.

Stereotaxic mapping of the monoamine pathways in the rat brain.

Disruption of the mouse dopamine transporter gene results in spontaneous hyperlocomotion despite major adaptive changes, such as decreases in neurotransmitter and receptor levels. In homozygote mice, dopamine persists at least 100 times longer in the extracellular space, explaining the biochemical basis of the hyperdopaminergic phenotype and demonstrating the critical role of the transporter in regulating neurotransmission. The dopamine transporter is an obligatory target of cocaine and amphetamine, as these psychostimulants have no effect on locomotor activity or dopamine release and uptake in mice lacking the transporter.

Hyperlocomotion and indifference to cocaine and amphetamine in mice lacking the dopamine transporter

Brain dopamine and the syndromes of Parkinson and Huntington. Clinical, morphological and neurochemical correlations.

G protein-coupled dopamine receptors (D1, D2, D3, D4, and D5) mediate all of the physiological functions of the catecholaminergic neurotransmitter dopamine, ranging from voluntary movement and reward to hormonal regulation and hypertension. Pharmacological agents targeting dopaminergic neurotransmission have been clinically used in the management of several neurological and psychiatric disorders, including Parkinson's disease, schizophrenia, bipolar disorder, Huntington's disease, attention deficit hyperactivity disorder (ADHD(1)), and Tourette's syndrome. Numerous advances have occurred in understanding the general structural, biochemical, and functional properties of dopamine receptors that have led to the development of multiple pharmacologically active compounds that directly target dopamine receptors, such as antiparkinson drugs and antipsychotics. Recent progress in understanding the complex biology of dopamine receptor-related signal transduction mechanisms has revealed that, in addition to their primary action on cAMP-mediated signaling, dopamine receptors can act through diverse signaling mechanisms that involve alternative G protein coupling or through G protein-independent mechanisms via interactions with ion channels or proteins that are characteristically implicated in receptor desensitization, such as β-arrestins. One of the future directions in managing dopamine-related pathologic conditions may involve a transition from the approaches that directly affect receptor function to a precise targeting of postreceptor intracellular signaling modalities either directly or through ligand-biased signaling pharmacology. In this comprehensive review, we discuss dopamine receptor classification, their basic structural and genetic organization, their distribution and functions in the brain and the periphery, and their regulation and signal transduction mechanisms. In addition, we discuss the abnormalities of dopamine receptor expression, function, and signaling that are documented in human disorders and the current pharmacology and emerging trends in the development of novel therapeutic agents that act at dopamine receptors and/or on related signaling events.

The Physiology, Signaling, and Pharmacology of Dopamine Receptors

The distribution of noradrenaline und dopamine (3-hydroxytyramine) in human adult and newborn brains has been investigated. The greatest amounts of noradrenaline were found in the hypothalamus, the central gray matter of the mesencephalon, the reticular formation and in the area postrema. The highest amount of dopamine was found in the neostriatum.

H. Ehringer

Papers

[Distribution of noradrenaline and dopamine (3-hydroxytyramine) in the human brain and their behavior in diseases of the extrapyramidal system].

Distribution of noradrenaline and dopamine (3-hydroxytyramine) in the human brain and their behavior in diseases of the extrapyramidal system.