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.

Parkinson's disease: Mechanisms and models

Objective: Parkinson’s disease (PD) is a progressive neurological disorder characterised by a large number of motor and non-motor features that can impact on function to a variable degree. This review describes the clinical characteristics of PD with emphasis on those features that differentiate the disease from other parkinsonian disorders. Methods: A MedLine search was performed to identify studies that assess the clinical characteristics of PD. Search terms included “Parkinson’s disease”, “diagnosis” and “signs and symptoms”. Results: Because there is no definitive test for the diagnosis of PD, the disease must be diagnosed based on clinical criteria. Rest tremor, bradykinesia, rigidity and loss of postural reflexes are generally considered the cardinal signs of PD. The presence and specific presentation of these features are used to differentiate PD from related parkinsonian disorders. Other clinical features include secondary motor symptoms (eg, hypomimia, dysarthria, dysphagia, sialorrhoea, micrographia, shuffling gait, festination, freezing, dystonia, glabellar reflexes), non-motor symptoms (eg, autonomic dysfunction, cognitive/neurobehavioral abnormalities, sleep disorders and sensory abnormalities such as anosmia, paresthesias and pain). Absence of rest tremor, early occurrence of gait difficulty, postural instability, dementia, hallucinations, and the presence of dysautonomia, ophthalmoparesis, ataxia and other atypical features, coupled with poor or no response to levodopa, suggest diagnoses other than PD. Conclusions: A thorough understanding of the broad spectrum of clinical manifestations of PD is essential to the proper diagnosis of the disease. Genetic mutations or variants, neuroimaging abnormalities and other tests are potential biomarkers that may improve diagnosis and allow the identification of persons at risk.

https://jnnp.bmj.com/content/jnnp/79/4/368.full.pdf

Parkinson’s disease: clinical features and diagnosis

Mutations in the α-synuclein gene ( SNCA ) in the Contursi kindred ([ 1 ][1]) implicated this gene in Parkinson's disease (PD). Subsequently, α-synuclein was identified as the major component of Lewy bodies, the pathological hallmark of PD, and of glial cell cytoplasmic inclusions ([ 2 ][2]).

We

/pdf/a-synuclein-locus-triplication-causes-parkinson-s-disease-4rg8t4thvs.pdf

α-Synuclein Locus Triplication Causes Parkinson's Disease

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.

Autografting of dopamine-producing adrenal medullary tissue to the striatal region of the brain is now being attempted in patients with Parkinson's disease. Since the success of this neurosurgical approach to dopamine-replacement therapy may depend on the selection of the most appropriate subregion of the striatum for implantation, we examined the pattern and degree of dopamine loss in striatum obtained at autopsy from eight patients with idiopathic Parkinson's disease. We found that in the putamen there was a nearly complete depletion of dopamine in all subdivisions, with the greatest reduction in the caudal portions (less than 1 percent of the dopamine remaining). In the caudate nucleus, the only subdivision with severe dopamine reduction was the most dorsal rostral part (4 percent of the dopamine remaining); the other subdivisions still had substantial levels of dopamine (up to approximately 40 percent of control levels). We propose that the motor deficits that are a constant and characteristic feature of idiopathic Parkinson's disease are for the most part a consequence of dopamine loss in the putamen, and that the dopamine-related caudate deficits (in "higher" cognitive functions) are, if present, less marked or restricted to discrete functions only. We conclude that the putamen--particularly its caudal portions--may be the most appropriate site for intrastriatal application of dopamine-producing autografts in patients with idiopathic Parkinson's disease.

https://www.nejm.org/doi/pdf/10.1056/NEJM198804073181402?listPDF=true

Uneven pattern of dopamine loss in the striatum of patients with idiopathic Parkinson's disease. Pathophysiologic and clinical implications.

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.

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

The whole body of evidence discussed in this article shows that brain dopamine can be regarded as a strong candidate for a physiologically active substance, regulating the functioning of some extrapyramidal centers, especially substantia nigra, striatum and pallidum. The following findings provide strong support for this view: The dopamine is mainly confined to the extrapyramidal regions mentioned; in these regions, the amine is localized in specific neurons and nerve terminals; its rate of turnover is of a high order of magnitude; is there a correlation between itsconcentration in the brain and the functional state of the extrapyramidal centers following administration of certain drugs; there is a striking relationship between some extrapyramidal disorders (drug-induced and genuine parkinsonism) and the lack of the amine in the substantia nigra, the striatum and the pallidum; and, finally, that substantia nigra exerts a direct influence on the concentration of the amine in the striatum by virtue of the nigro-striatal dopamine-containing fibers.

In the extrapyramidal centers, dopamine may have either inhibitory or excitatory activity. Neurophysiological evidence obtained in different species points to a predominantly inhibitory activity of dopamine on single neurons of the brain.

Evidence showing that in the retina and in the median eminence (including the pituitary stalk) dopamine may be the predominant catecholamine argues in favor of a specific function of the amine in these brain structures, although there are at present no direct findings to prove this suggestion.

From the evidence discussed in this article a good case can be made for the concept that the physiological activity of the brain dopamine is quite different from that of brain norepinephrine. There are as yet., however, no experiments to positively show that dopamine is a true neuro-transmitter substance in the brain. All central dopamine effects could equally well be explained by assuming that the amine is a modifier of synaptic transmission.

Therefore, in order to establish dopamine unequivocally as a central neurotransmitter substance, there is still one crucial experiment to be done: to demonstrate that upon stimulation of the relevant parts of the brain, dopamine is in fact released at synapses to exert by itself an effect on the neurons standing in synaptic relationship with the stimulated dopamine-containing terminals. It is to be hoped that we shall not have to wait too long for this experiment to be performed.

Dopamine (3-hydroxytyramine) and brain function

Biochemical pathophysiology of Parkinson's disease.

The importance of the striatal dopamine (DA) deficiency and the DA substituting property of levodopa for the pathophysiology and therapy of Parkinson9s disease (PD) is reiterated. In addition, it is shown that in PD, significantly reduced DA levels are also found in the nucleus accumbens, external and internal segments of the globus pallidus, the substantia nigra reticulata, and the subthalamic nucleus. It is proposed that, in addition to the critical role played by the striatal DA loss, the DA changes in the extrastriatal nuclei of the basal ganglia are importantly involved in the pathophysiologic mechanisms resulting in the parkinsonian movement disorder, and that the therapeutic and/or side effects of DA substitution therapy may, in part, be mediated through these brain regions which, like the striatum, suffer DAergic deafferentation in PD. From observations in brain of patients with secondary parkinsonism, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine parkinsonism in the rhesus monkey, as well as the regional DA transporter distribution in the primate substantia nigra, it is concluded that PD may be caused by any exogenous and/or endogenous toxin using the transporter system for DA and to some degree the other brain monoamines (noradrenaline, serotonin), to enter, and damage, the respective monoamine neurons. Based on converging evidence, the view is advanced that endogenous, genetically based(excessive) formation, or accumulation, of toxic DA transporter substrates, such as isoquinoline or β-carboline derivatives, may in fact represent the primary cause of substantia nigra cell degeneration in patients with PD.

Oleh Hornykiewicz

Papers

Uneven pattern of dopamine loss in the striatum of patients with idiopathic Parkinson's disease. Pathophysiologic and clinical implications.

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

Dopamine (3-hydroxytyramine) and brain function

Biochemical pathophysiology of Parkinson's disease.

Biochemical aspects of Parkinson's disease