Tyrosine hydroxylase immunohistochemistry in human brain

Heterogeneity of dopamine release sites in health and degeneration

Despite comprising only ~ 0.001% of all neurons in the human brain, ventral midbrain dopamine neurons exert a profound influence on human behavior and cognition. As a neuromodulator, dopamine selectively inhibits or enhances synaptic signaling to coordinate neural output for action, attention, and affect. Humans invariably lose brain dopamine during aging, and this can be exacerbated in disease states such as Parkinson's Disease. Further, it is well established in multiple disease states that cell loss is selective for a subset of highly sensitive neurons within the nigrostriatal dopamine tract. Regional differences in dopamine tone are regulated pre-synaptically, with subcircuits of projecting dopamine neurons exhibiting distinct molecular and physiological signatures. Specifically, proteins at dopamine release sites that synthesize and package cytosolic dopamine, modulate its release and reuptake, and alter neuronal excitability show regional differences that provide linkages to the observed sensitivity to neurodegeneration. The aim of this review is to outline the major components of dopamine homeostasis at neurotransmitter release sites and describe the regional differences most relevant to understanding why some, but not all, dopamine neurons exhibit heightened vulnerability to neurodegeneration.

Noradrenaline microinjected into the dorsal periaqueductal gray matter causes anxiolytic-like effects in rats tested in the elevated T-maze

AIMS

The dorsal periaqueductal gray matter (dPAG) is involved in the integration of behavioral and cardiovascular responses caused by fear and anxiety situations. Some studies suggest an involvement of noradrenergic neurotransmission in the dPAG in anxiety modulation, however, there is no evidence about its role in panic attacks. The goal of this work was to study the effect of NA microinjection in dPAG in rats submitted to the elevated T-maze (ETM).

MATERIALS AND METHODS

Male Wistar had a cannula implanted in the PAG where it was injected NA in the doses of 1, 3, 15, 45nmol/50nl or artificial cerebrospinal fluid previous the ETM test.

KEY FINDINGS

NA intra-dPAG decreased inhibitory avoidance behavior in the ETM without changing escape, indicating only an anxiolytic-like effect. Furthermore, the microinjection of NA did not change the general exploratory activity of the animals submitted to the open field test, suggesting that the anxiolytic-like effect is not due to an increase in exploratory activity.

SIGNIFICANCE

The results indicate an involvement of noradrenergic neurotransmission in the dPAG in defensive reactions associated with generalized anxiety, but not as main mechanisms for the panic, in rats submitted to the elevated T-maze providing support for other research aimed at improving the treatment of generalized anxiety.

Aromatic L-amino acid decarboxylase-immunoreactive structures in human midbrain, pons, and medulla

The objective of the present study was to determine with precision the localization of neurons and fibers immunoreactive (ir) for aromatic L-amino acid decarboxylase (AADC), the second-step enzyme responsible for conversion of L-dihydroxyphenylalanine (L-DOPA) to dopamine (DA) and 5-hydroxytryptophan (5-HTP) to serotonin (5-hydroxytryptamine: 5-HT) in the midbrain, pons, and medulla oblongata of the adult human brain. Intense AADC immunoreactivity was observed in a large number of presumptive 5-HT neuronal cell bodies distributed in all of the raphe nuclei, as well as in regions outside the raphe nuclei such as the ventral portions of the pons and medulla. Moderate to strong immunoreaction was observable in presumptive DA cells in the mesencephalic reticular formation, substantia nigra, and ventral tegmental area of Tsai, as well as in presumptive noradrenergic (NA) cells, which were aggregated in the locus coeruleus and dispersed in the subcoeruleus nuclei. In the medulla oblongata, immunoreaction of moderate intensity was distributed in the mid and ventrolateral portions of the intermediate reticular nucleus, which constitutes the oblique plate of A1/C1 presumptive adrenergic and/or NA neurons. The dorsal vagal AADC-ir neurons were fewer in number and stained more weakly than cells immunoreactive for tyrosine hydroxylase (TH). AADC immunoreactivity was not identified in an aggregate of TH-ir neurons lying in the gelatinous subnucleus of the solitary nucleus, a restricted region just rostroventral to the area postrema. Nonaminergic AADC-positive neurons (D neurons), which are abundant in the rat and cat midbrain, pons, and medulla, were hardly detectable in homologous regions in the human brain, although they were clearly distinguishable in the forebrain.

High-frequency stimulation of the subthalamic nucleus prolongs the increase in striatal dopamine induced by acute l-3,4-dihydroxyphenylalanine in dopaminergic denervated rats

High-frequency stimulation of the subthalamic nucleus (STN-HFS) is a powerful approach for treating the motor symptoms of Parkinson's disease (PD). It results in clinical improvement in patients with PD, further reducing the l-3,4-dihydroxyphenylalanine (L-DOPA) requirement and thus L-DOPA-induced dyskinesia. However, it remains unclear how STN-HFS modifies the response to L-DOPA. We investigated the effect of STN-HFS on striatal extracellular concentrations of dopamine and its metabolites following acute L-DOPA administration in intact or partially dopaminergic denervated (DA-PL) rats. L-DOPA treatment significantly increased striatal dopamine levels in intact and DA-PL animals, with the maximal effect observed 1 h after L-DOPA injection. This increase was more pronounced in DA-PL rats (ipsilateral to the lesion) than in intact animals. It remained fairly stable 1 h after the maximal effect of L-DOPA and then decreased towards basal values. STN-HFS in intact rats had no effect on the maximal L-DOPA-induced increase in striatal extracellular dopamine concentration or the return to basal values, the profiles observed being similar to those for non-stimulated intact animals. Conversely, STN-HFS amplified the L-DOPA-induced increase in striatal dopamine levels during the stimulation period (1 h) in DA-PL rats and this increase was sustained throughout the post-stimulation period (2.5 h), without the return to basal levels observed in stimulated intact and non-stimulated rats. These new neurochemical data suggest that STN-HFS interferes with L-DOPA effects, probably synergically, by stabilizing dopamine levels in the striatum and shed light on the mechanisms of STN-HFS in PD.

Locus coeruleus neurofibrillary degeneration in aging, mild cognitive impairment and early Alzheimer's disease

Neurofibrillary degeneration in the nucleus basalis and a loss of its cortical cholinergic projections are prominent components of the neuropathology in Alzheimer's disease (AD). The AD brain is also associated with a degeneration of the noradrenergic projections arising from the nucleus locus coeruleus (LC), but the time course of this lesion is poorly understood. To determine whether the LC displays neurofibrillary abnormalities early in the course of events leading to AD, we examined tissue specimens from seven cognitively normal controls and five subjects at the stages of mild cognitively impairment (MCI) or early AD. Tyrosine hydroxylase immunochemistry was used as a marker of LC neurons while AT8 immunolabeling visualized abnormal tau associated with neurofibrillary tangles and their precursors. Thioflavine-S was used as a marker for fully developed tangles. We found that AT8-positive labeling and thioflavine-S positive tangles were present in both groups of specimens. However, the percentage of neurons containing each of these markers was significantly higher in the cognitively impaired group. The MMSE scores displayed a negative correlation with both markers of cytopathology. These results indicate that cytopathology in the LC is an early event in the age-MCI-AD continuum and that it may be listed among the numerous factors that mediate the emergence of the cognitive changes leading to dementia.

Dopaminergic innervation of the human striatum in Parkinson's disease

In Parkinson's disease (PD), dopaminergic input to the caudate nucleus and a band of putaminal tissue abutting the external globus pallidus seems well preserved on immunohistochemical staining for the dopamine transporter. Counting of dopaminergic terminals showed that terminal density in these regions in PD was the same as that in controls, which indicates that input is truly preserved and not a consequence of a compensatory upregulation of metabolism in a reduced pool of surviving terminals. When the branching pattern of dopaminergic axons coursing through the globus pallidus was examined, we found no evidence for increased axonal sprouting in PD that might have contributed to preservation of dopaminergic input to the putamen or caudate nucleus. Although terminal counting indicated that anatomic input was preserved to parts of the striatum, dopamine uptake site density in these regions was reduced significantly. This suggests that the impact of disease in these areas is more profound than was thought previously.

Catecholaminergic neurons in the brain-stem and sleep apnea in SIDS victims

BACKGROUND

Tyrosine hydroxylase (TH) is a specific marker for catecholaminergic neurones. Some reports have demonstrated a decrease of TH in the Sudden Infant Death Syndrome (SIDS) compared with controls. To further investigate this, the correlation between TH and sleep apnea was investigated here.

MATERIALS AND METHODS

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age. They included 26 cases of SIDS. All the infants had been recorded during one night in a pediatric sleep laboratory some 3 to 12 weeks before death. The frequency and the duration of sleep apnea were analyzed. The brain stem material was collected and subjected to immunohistochemical studies for TH. The density of TH-immunoreactive neurons was measured in the nucleus hypoglossus, nervus vagus dorsalis, solitary and ambiguous and the ventrolateral medulla (VLM) in the medulla oblongata. Correlation analyses were carried out between the density of TH-immunoreactive neurons and the data from the sleep apnea studies.

RESULTS

There was no SIDS specific correlation between TH-immunoreactive neurons in the nucleus hypoglossus, nervus vagus dorsalis, solitary and ambiguous and the ventrolateral medulla (VLM) in the medulla oblongata and the frequency and duration of sleep apnea.

CONCLUSIONS

No significant association between the pathological data and the physiological data refers to TH positive neurons in the medulla oblongata in SIDS victims.

Developmental neurotransmitter pathology in the brainstem of sudden infant death syndrome: a review and sleep position

Developmental studies on neurotransmitters and their receptors in sudden infant death syndrome (SIDS) infants and controls are reviewed, including comparison between the prone and supine positions at death. In SIDS infants, there are an increase of glial fibrillary acidic protein (GFAP)-positive astrocytes in the brainstem, an increase of substance P (SP) in the medulla and pons, a decrease of tyrosine hydroxylase (TH)-positive catecholaminergic neurons in the ventrolateral medulla (VLM), and vagal nuclei in the medulla oblongata and basal ganglia, a decrease of tryptophan hydroxylase (TrH)-positive serotonergic neurons in the periaqueductal gray matter (PAG), and decreases of 5-hydroxytryptamine 1A (5-HT1A) and 5-HT2A receptor immunoreactivities in the VLM and vagal nuclei in the medulla oblongata. These findings may be the result of chronic or repeated hypoxia and at the same time suggest hypofunction or immaturity of cardiorespiratory regulation. In contrast, 5-HT1A and 5-HT2A receptor immunoreactivities are increased in the PAG of SIDS infants. These increased immunoreactivities may reflect delayed neuronal maturation or a developmental abnormality of the nocicetive reaction of cardiorespiratory and arousal control in SIDS. Also, there are no differences of brainstem gliosis and catecholaminergic neuron changes between the prone and supine positions. Therefore, these changes may be predisposing factors for SIDS.

Familial dysautonomia: a 47-year perspective. How technology confirms clinical acumen

A historical perspective of familial dysautonomia is presented, highlighting the early contributions of Dr. Joseph Dancis. As further investigations proceeded, his original observations have withstood the test of time and may contribute to determining the molecular abnormality in this rare genetic disorder. Dr. Dancis's work in this area serves as a model of how observations based on clinical acumen and critical thinking can be verified by future technological advances.

Pattern of plasma levels of catecholamines in familial dysautonomia

This report extends previous investigations of endogenous catecholamine levels in patients with orthostatic hypotension due to familial dysautonomia (FD), to define better the neurochemical phenotype and elucidate possible pathophysiological mechanisms. Ten FD patients (age 26.1 +/- 2.6 (SEM) years) and eight control subjects (age 29.5 +/- 3.7 years) were studied. Heart rate, blood pressure and venous blood samples were obtained while supine and after 5 min in the upright position. Plasma levels of dihydroxyphenylalanine (DOPA), noradrenaline (NA), adrenaline (A), dopamine (DA), dihydroxyphenylglycol (DHPG) and dihydroxyphenylacetic acid (DOPAC) were measured. When supine, the FD group had greater NA and DOPA levels, and lower DHPG levels. Plasma NA did not increase with erect posture in FD patients. Individual FD mean blood pressures were correlated positively with plasma NA levels when supine and with plasma DA and DOPAC when upright. In FD, DOPA:DHPG ratios were above the range found in normal subjects or that reported in patients with acquired forms of dysautonomia regardless of posture, whereas DOPAC:DHPG ratios remained normal. Thus FD patients have a characteristic neurochemical pattern which probably reflects either decreased vesicular storage of catecholamines or limited oxidative deamination despite normal or increased tyrosine hydroxylation.

Dopamine-beta-hydroxylase and tyrosine hydroxylase immunoreactive neurons in the human brainstem

Immunohistochemistry of dopamine-beta-hydroxylase in the human hind brain indicates that neuronal cell bodies containing the antigen form prominent populations in the nucleus tractus solitarius and nearby medial and dorsal edge of the medial vestibular nucleus. They are frequent in and around the periphery of the dorsal motor nucleus of the vagus and in an oblique band extending from that region to the ventrolateral aspect of the reticular formation, where they are most numerous at the mid medullary levels. Dopamine-beta-hydroxylase immunoreactive neurons are also closely packed in the nuclei coeruleus and subcoeruleus. Concomitant immunohistochemistry for tyrosine hydroxylase demonstrates small numbers of neuronal cell bodies that are reactive only for this antigen, and which do not contain detectable dopamine-beta-hydroxylase. Such neurons are present in the nucleus tractus solitarius, the pontine lateral parabrachial nucleus and within the core of the rostral pontine reticular formation. Some medullary and pontine axon bundles similarly stain for tyrosine hydroxylase but not for dopamine-beta-hydroxylase. These differential staining patterns suggest, among other possibilities, that in humans some neurons of the caudal brainstem are dopamine (if they contain the second step catecholamine synthesizing enzyme, aromatic L-aminoacid decarboxylase) rather than noradrenaline or adrenaline containing catecholamine neurotransmitters.

Functional characteristics of the midbrain periaqueductal gray

The major functions of the midbrain periaqueductal gray (PAG), including pain and analgesia, fear and anxiety, vocalization, lordosis and cardiovascular control are considered in this review article. The PAG is an important site in ascending pain transmission. It receives afferents from nociceptive neurons in the spinal cord and sends projections to thalamic nuclei that process nociception. The PAG is also a major component of a descending pain inhibitory system. Activation of this system inhibits nociceptive neurons in the dorsal horn of the sinal cord. The dorsal PAG is a major site for processing of fear and anxiety. It interacts with the amygdala and its lesion alters fear and anxiety produced by stimulation of amygdala. Stimulation of PAG produces vocalization and its lesion produces mutism. The firing of many cells within the PAG correlates with vocalization. The PAG is a major site for lordosis and this role of PAG is mediated by a pathway connecting the medial preoptic with the PAG. The cardiovascular controlling network within the PAG are organized in columns. The dorsal column is involved in pressor and the ventrolateral column mediates depressor responses. The major intrinsic circuit within the PAG is a tonically-active GABAergic network and inhibition of this network is an important mechanism for activation of outputs of the PAG. The various functions of the PAG are interrelated and there is a significant interaction between different functional components of the PAG. Using the current information about the anatomy, physiology, and pharmacology of the PAG, a model is proposed to account for the interactions between these different functional components.

Quantitative analysis of immunohistochemical distributions of cholinergic and catecholaminergic systems in the human brain

The distributions of the cholinergic system and catecholaminergic system in the normal human brain were analysed quantitatively by a microphotometry system. Consecutive coronal sections were obtained from the anterior area of the left hemisphere and were stained alternately with fluorescent immunohistochemical staining for choline acetyltransferase or tyrosine hydroxylase. Each stained section was divided into approximately 120,000 areas and the fluorescence intensity in each area was measured by a fluorescence microphotometry system which is a measuring microscope for distribution of fluorescence intensity in the tissue slice. Nonspecific autofluorescence was distributed in myelinated nerve fiber throughout the entire area, which was subtracted from the fluorescence intensity value in each measuring area. The obtained immunohistochemical fluorescence intensities of choline acetyltransferase and tyrosine hydroxylase were classified into eight ranks and were indicated by color graphics. Also, the intensity values of actual immunohistochemical fluorescence in the various brain regions were presented. The choline acetyltransferase and tyrosine hydroxylase concentrations varied greatly depending on the brain region. Relatively high levels of choline acetyltransferase and tyrosine hydroxylase were distributed in the putamen, caudate nucleus, claustrum, insula and some cortical regions. The immunohistochemical level of tyrosine hydroxylase was lower than that of choline acetyltransferase in a few brain regions such as the globus pallidus and amygdala. High levels of choline acetyltransferase and tyrosine hydroxylase were localized in the one area of the basal ganglia which developed from the telencephalic area, whereas middle levels of these were distributed in another, part of which developed from the diencephalic area.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative light microscopic autoradiographic localization of alpha 2-adrenoceptors in the human brain

In the present work the anatomical distribution of alpha 2-adrenoceptors in the human central nervous system was studied in detail by quantitative autoradiography using the selective alpha 2 agonist [3H]bromoxidine ([3H]UK-14304) as a ligand. Only postmortem tissues from subjects free of neurological disorders were used in this study. Very high or high densities of alpha 2-adrenoceptors were found along layers I and III in non-visual neocortex, layers III and IVc of the visual cortex, CA1 field--stratum lacunosum-moleculare--and dentate gyrus--stratum granularis--at the hippocampal formation, nucleus arcuatus at the hypothalamus, locus ceruleus, nucleus dorsalis of vagus and at the stratum granularis of the cerebellar cortex. Relevant densities of alpha 2-adrenoceptors were also observed along the remaining layers of neocortex, nuclei centralis, medialis and corticalis at the amygdala, anterior thalamic group and rotundocellularis nuclei, paraventricular and ventromedial hypothalamic nuclei, substantia innominata, superior colliculus--stratum zonale--and lateral periaqueductal area at the midbrain, nucleus tractus solitarii and dorsal horn--substantia gelatinosa--of the spinal cord. [3H]Bromoxidine specific binding was very low or negligible in the remaining brain areas. Although a general parallelism between the distribution of these receptors could be observed for the rat and human brain, dramatic species differences in the level of alpha 2-receptors were found in several brain areas, such as thalamus, amygdala or cerebellar cortex. In general, the distribution of alpha 2-adrenoceptors in the human brain found here was parallel to that described for the noradrenergic presynaptic terminals in the mammalian central nervous system, lending some weight to the proposed predominant presynaptic localization of these receptors. The relevance of the anatomical distribution of alpha 2-adrenoceptors in the human brain for a better knowledge of the neurochemistry of neuropsychiatric disorders is discussed.

Neurotransmitter transporters (plus): a promising new gene family

Neurotransmitter transporter genes encode proteins with 12 putative transmembrane regions, which mediate Na(+)-dependent reaccumulation of released neurotransmitters into presynaptic terminals and are the sites of action of important abused and therapeutic drugs. Studies of these genes show promise for improving our understanding of transport mechanisms and modes of drug action, and may even uncover previously unanticipated neurotransmitters.

Distribution of catecholamine uptake sites in human brain as determined by quantitative [3H] mazindol autoradiography

Because of the importance of the catecholamine system in Parkinson's disease and its relevance to a variety of clinical movement disorders, catecholamine uptake sites were mapped in the human brain using [3H] mazindol autoradiography. Displacement studies with known dopamine (DA) and noradrenaline (NA) uptake blockers showed that binding in the striatum was to dopamine uptake sites; binding in the locus coeruleus was to noradrenergic uptake sites. By using the selective noradrenergic uptake blocker desmethylimipramine (DMI), a comprehensive map of both DA and NA uptake sites was generated. In general, catecholamine uptake sites were better seen in terminals than in cells of origin or axonal projections. In some areas, such as the locus coeruleus, punctate binding could be seen over individual pigmented cells. A variegated pattern of binding was seen in caudate nucleus and putamen and some correspondence of patches of low binding with striosomes was observed in the caudate. The highest levels of binding to DA uptake sites was observed in the striatum, where regional differences in binding occurred. The most dense binding was seen in the ventral striatum, and a rostral-to-caudal decrement in binding levels in caudate nucleus and putamen was evident. Binding was more intense in the putamen compared to the caudate and within the caudate lower values were seen laterally. The highest levels of binding to noradrenergic uptake sites were in the locus coeruleus and dorsal raphé, although these sites may be on terminals from other projections. Whereas uptake sites were more often evident in known catecholamine pathways, [3H] mazindol binding was seen in some areas where catecholamine neurons or terminals had not been identified previously. These maps of the catecholamine uptake system add further information concerning the nature of the distribution of catecholamines in human brain and provide an important baseline for the study of disease and ageing processes.

Tyrosine hydroxylase-immunoreactive neurons in the temporal lobe in complex partial seizures

The anterior mesial portion of the temporal lobe removed from 16 patients who underwent surgery for the treatment of complex partial seizures was found to contain tyrosine hydroxylase-immunoreactive neurons. The distribution of these neurons was correlated with the underlying neuropathological features. Ammon's horn sclerosis was present in 8 patients; a ganglioglioma, in 7 patients; and an infarction in the distribution of the middle cerebral artery, in 1 patient. Tyrosine hydroxylase-immunoreactive neurons were found in Ammon's horn of 6 of the 8 patients with Ammon's horn sclerosis, and in the subiculum and entorhinal cortex of all 8 patients with the same pathology. None of these neurons were found in Ammon's horn of the 7 patients with a ganglioglioma, but were found in the subiculum of 5 of the 7 patients and in entorhinal cortex of all 7 patients. Tyrosine hydroxylase immunoreactivity was also studied in 13 control autopsy specimens. No tyrosine hydroxylase-immunoreactive neurons were found in Ammon's horn or the subiculum of any of the control specimens, but were found in the entorhinal cortex of 6 of the 13 specimens. The tyrosine hydroxylase-immunoreactive neurons in the mesial portion of the temporal lobe of patients with complex partial seizures may contribute to the increased levels of tyrosine hydroxylase found in neurochemical studies of specimens taken at temporal lobectomy.

Catecholamine-containing neurons in the sheep brainstem and diencephalon: immunohistochemical study with tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) antibodies

The present study describes the distribution and morphological characteristics of neurons and nerve fibers containing the catecholamine-synthesizing enzymes, tyrosine hydroxylase and dopamine-beta-hydroxylase, in the sheep brainstem and diencephalon on the basis of immunohistochemical procedures. Neurons and fibers were considered to be dopaminergic if they showed anti-tyrosine hydroxylase immunoreactivity, without corresponding anti-dopamine-beta-hydroxylase immunoreactivity. The structures labeled with both antisera were considered noradrenergic or adrenergic. The distribution of catecholaminergic neurons corresponds to that described by other authors with similar methods in the rat and in primates. The noradrenergic neurons belong to cell groups A1 to A7 and the dopaminergic neurons to cell groups A8 to A15. In almost all studied areas, the catecholaminergic innervation is similar to that observed in the other species. However, the central catecholaminergic systems of the sheep showed some specific characteristics: (1) groups A3 and A4, described in the rat, were not found, (2) group A14 contains fewer neurons than in the rat, (3) group A15 does not contain a dorsal but only a ventral portion, (4) there is a larger dispersion of neurons within each group, especially A6 and A7, than in rodents, and (5) there is a larger noradrenergic innervation of the catecholaminergic groups than in the other species.

Dopaminergic innervation of the basal ganglia in the squirrel monkey as revealed by tyrosine hydroxylase immunohistochemistry

The organization of the dopaminergic mesostriatal fibers and their patterns of innervation of the basal ganglia in the squirrel monkey (Saimiri sciureus) were studied immunohistochemically with an antiserum raised against tyrosine hydroxylase (TH). Numerous fibers arose from midbrain TH-positive cell bodies of the substantia nigra pars compacta (group A9), the retrorubral area (group A8), and the lateral portion of the ventral tegmental area (group A10). These fibers accumulated dorsomedially to the rostral pole of the substantia nigra where they formed a massive bundle that coursed through the prerubral field and ascended along the laterodorsal aspect of the medial fore-brain bundle in the lateral hypothalamus. Some ventrally located fibers ran throughout the rostrocaudal extent of the lateral preopticohypothalamic area and could be followed up to the olfactory tubercle, whereas other fibers turned laterodorsally to invade the head of the caudate nucleus. At more dorsal levels in the lateral hypothalamus, many fiber fascicles detached themselves from the main bundle and swept laterally to reach the globus pallidus, the putamen, and the amygdala. Several TH-positive fibers coursed along the dorsal surface of the subthalamic nucleus, and some invaded the dorsomedial third of this structure. The remaining portion of the subthalamic nucleus contained relatively few TH-positive elements. In contrast, the globus pallidus received a dense dopaminergic innervation deriving mostly from two fascicles that coursed backward along the two major output pathways of the pallidum: the lenticular fasciculus caudodorsally and the ansa lenticularis rostroventrally. At the pallidal level, the labeled fibres merged within the medullary laminae and arborized profusely in the internal pallidal segment and less abundantly in the external pallidal segment. However, the caudoventral portion of the external pallidum displayed a dense field of TH-positive axonal varicosities. Other fibers ran through the dorsal two-thirds of the external pallidum en route to the putamen. The striatum contained a multitude of thin axonal varicosities among which a few long and varicosed fibers were scattered. These immunoreactive neuronal profiles were rather uniformly distributed along the rostrocaudal extent of the striatum but appeared slightly more numerous in the ventral striatum than in the dorsal striatum. The pattern of distribution of the TH-positive axonal varicosities in the dorsal striatum was markedly heterogeneous: it consisted of typical zones of poor TH immunoreactivity lying within a matrix of dense terminal labeling.(ABSTRACT TRUNCATED AT 400 WORDS)

Selective vulnerability of pigmented dopaminergic neurons in Parkinson's disease

From a neuropathological point, the diagnosis of Parkinson's disease is confirmed by a neuronal cell loss and the presence of Lewy bodies in the substantia nigra. In Parkinson's disease, the precise type of nigral neuron which degenerate still remains unknown. Are all types of neuron similarly injured, are only subpopulations of neurons vulnerable? In an attempt to answer the question, a qualitative and quantitative analysis of the distribution of dopaminergic cells, as identified by immunohistochemistry with a specific antibody against tyrosine hydroxylase, was performed in the ventral mesencephalon of control subjects and patients who died with a clinical diagnosis of Parkinson's disease. In control brains, two types of catecholaminergic neurons were evidenced; some contain visible-neuromelanin, others do not. In patients with Parkinson's disease, the tyrosine hydroxylase positive cells which contained the pigment were the most vulnerable.

Distribution of phenylethanolamine N-methyltransferase cell bodies, axons, and terminals in monkey brainstem: an immunohistochemical mapping study

Adrenaline (epinephrine) is an important candidate transmitter in descending spinal control systems. To date intrinsic spinal adrenergic neurons have not been reported; thus adrenergic input is presumably derived from brainstem sites. In this regard, the localization of adrenergic neurons in the brainstem is an important consideration. Maps of adrenergic cell bodies and to a lesser extent axons and terminal fields have been made in various species, but not in monkeys. Thus, the present study concerns the organization of adrenergic systems in the brainstem of a monkey (Macaca fascicularis) immunohistochemically mapped by means of an antibody to the enzyme phenylethanolamine N-methyltransferase (PNMT). PNMT-immunostained cell bodies are distributed throughout the medulla in two principal locations. One concentration of labeled cells is in the dorsomedial medulla and includes the nucleus of the solitary tract (NTS), the dorsal motor nucleus of the vagus (X), and an area ventral to X in a region of the reticular formation (RF) known as the central nucleus dorsalis (CnD) of the medulla. A few scattered cells are observed in the periventricular gray just ventral to the IVth ventricle and on midline in the raphe. The second major concentration of PNMT-immunostained cells is located in the ventrolateral RF, lateral and dorsolateral to the inferior olive (IO), including some cells in the rostral part of the lateral reticular nucleus (LRN). Terminal fields are located in the NTS, X, area postrema (AP), and the floor of the IVth ventricle in the medulla and pons. A light terminal field is also observed in the raphe, particularly raphe pallidus (RP). A heavy terminal field is present in locus coeruleus (LC). Fibers labeled for PNMT form two major fiber tracts. One is in the dorsomedial RF extending as a well-organized bundle through the medulla, pons, and midbrain. A second tract is located on the ventrolateral edge of the medulla and caudal pons. Fibers in this tract appear to descend to the spinal cord. A comparison with maps of other catecholamine neurons in primates is discussed, confirming that the distribution of the adrenergic system in monkeys is similar to that described in the human.

The human locus coeruleus complex: an immunohistochemical and three dimensional reconstruction study

The CA (catecholamine/catecholaminergic) cell populations of the locus coeruleus (LC) and subcoeruleus (SubC) were studied using serial sections of the human brainstem immunostained with an antibody against tyrosine hydroxylase. The tyrosine hydroxylase-immunoreactive (TH-IR) neurons were plotted in a computer reconstruction system and their number and soma size determined. Serial section computer analysis was then used to create a three dimensional reconstruction of the LC complex. The number of cells containing neuromelanin pigment was also determined and compared with the number of TH-IR cells. In our sample there were 53,900 TH-IR cells in the LC and a further 6260 cells in the SubC. These numbers were very similar to our estimates of the number of cells containing neuromelanin pigment and we concluded that virtually all of these cells were also tyrosine hydroxylase positive. The average soma size of the TH-IR cells of the LC was 37 microns and in the SubC 34 microns. In addition to these quantitative observations the morphology of the TH-IR and the Nissl stained cells is described in some detail. We also compared the groups of immunoreactive cells in the human pons with the noradrenergic groups A5-A7 described in the rat. Although in the human these groups are contiguous, A5 is not part of the LC complex. However we did find that the A7 group is equivalent to the rostroventral part of SubC while the remainder of SubC is formed by ventral A6.

Localization of distinct monoamine oxidase A and monoamine oxidase B cell populations in human brainstem

Monoclonal antibodies, specific for either monoamine oxidases A or B, were used to determine the localization of monoamine oxidase in the human brain. Two distinct populations of neurons were detected by immunocytochemical staining. Neurons in regions rich in catecholamines were positive for monoamine oxidase A, including the nucleus locus coeruleus, the nucleus subcoeruleus and the medullary reticular formation. In these regions, monoamine oxidase A could be co-localized with the synthetic enzyme, dopamine-beta-hydroxylase. Neurons in the substantia nigra and the periventricular region of the hypothalamus, areas rich in dopamine neurons, stained for monoamine oxidase A but with much less frequency and intensity. The major accumulation of monoamine oxidase B-positive neurons was observed in the same regions in which monoamine oxidase B is found to co-localize with serotonin in monkey tissues, including the nucleus raphe dorsalis and the nucleus centralis superior. In addition, both monoamine oxidase A and B were localized in distinct populations of neurons in the lateral and tuberal regions of the hypothalamus, a region shown recently to contain histamine neurons in rats. Some glial cells were stained throughout the brain for monoamine oxidase A or B suggesting that glia are capable of either expression or uptake of these proteins.

The pigmented subpeduncular nucleus: a neuromelanin-containing nucleus in the human pontine tegmentum. Morphology and changes in Alzheimer's disease

A nuclear gray is found in the human pontine tegmentum close to the lower circumference of the superior cerebellar peduncle and is located within the pedunculo-lemniscal trigone. It is mainly characterized by the presence of medium-sized neuro-melanin-containing neurons and, therefore, referred to as the pigmented subpeduncular nucleus. Three basic neuronal types occur within the boundaries of the nucleus. Scattered among the neuromelanin-containing type I nerve cells are type II cells with lipofuscin deposits and type III neurons devoid of any pigmentation. In cases of Alzheimer-type dementia, the pigmented subpeduncular nucleus shows severe changes. Neurofibrillary tangles can frequently be found within the somata of both the melanin-laden and the lipofuscin-containing neurons. In contrast, the non-pigmented nerve cells remain devoid of such pathological filaments. Furthermore, large numbers of neuropil threads are scattered throughout the nuclear gray.

Immunocytochemical localization of dopamine-beta-hydroxylase in neurons of the human brain stem

The distribution of catecholaminergic cells in the human pons and medulla was illustrated by immunocytochemistry using a polyclonal antibody directed against the catecholamine synthetic enzyme, dopamine-beta-hydroxylase. The antibody specifically recognizes dopamine-beta-hydroxylase in putative adrenergic and noradrenergic neurons. The adrenergic and noradrenergic neurons are found in the brain stem from caudal levels of the medulla through the caudalmost levels of the midbrain. Large numbers of dopamine-beta-hydroxylase-positive cells were observed in cell groups of the medulla. Additionally, dopamine-beta-hydroxylase-positive cells were concentrated in the nucleus locus coeruleus and the nucleus subcoeruleus in the pons. These studies confirm that immunocytochemical localization of dopamine-beta-hydroxylase can be used to identify noradrenergic and adrenergic neurons and their terminal varicosities in the pons and medulla in routine autopsy material. These studies have also illustrated that the distribution of dopamine-beta-hydroxylase in the adult human brain is comparable to the distribution in other species.

A small proportion of cholinergic neurones in the nucleus basalis magnocellularis of ferret appear to stain positively for tyrosine hydroxylase

The immunofluorescence and peroxidase-antiperoxidase methods for immunohistochemistry were used to show that a small number of neurones in the nucleus basalis magnocellularis of ferret stain positively for what appears to be tyrosine hydroxylase, a marker for catecholaminergic neurones. With a double immunocytochemical staining method, it was confirmed that the tyrosine hydroxylase-like immunoreactivity is localized in neurones that also stain strongly for choline acetyltransferase.

Ventral tegmental (A10) system: neurobiology. 1. Anatomy and connectivity

The VTA contains the A10 group of DA containing neurons. These neurons have been grouped into nuclei to be found on the floor of the midbrain tegmentum--Npn, Nif, Npbp and Nln rostralis and caudalis. The VTA is traversed by many blood vessels and nerve fibers. Close to its poorly defined borders are found DA (A8, A9, A11) and 5-HT containing neurons (B8). Efferent projections of the VTA can be divided into 5 subsystems. The mesorhombencephalic projects to other monoaminergic nuclei, the cerebellum and a fine projection descends to other tegmental nuclei as far as the inferior olive. Fibers to the spinal cord have not been demonstrated. The mesodiencephalic path projects to several thalamic and hypothalamic nuclei and possibly the median eminence. Functionally important examples are the anterior hypothalamic-preoptic area, N. medialis dorsalis and reuniens thalami. These two subsystems are largely non-dopaminergic. A minor mesostriatal projection is overshadowed by the large mesolimbic projection to the accumbens, tuberculum olfactorium, septum lateralis and n. interstitialis stria terminalis. There are also mesolimbic connections with several amygdaloid nuclei (especially centralis and basolateralis), the olfactory nuclei and entorhinal cortex. A minor projection to the hippocampus has been detected. The mesocortical pathway projects to sensory (e.g. visual), motor, limbic (e.g. retrosplenial) and polysensory association cortices (e.g. prefrontal). Prefrontal, orbitofrontal (insular) and cingulate cortices receive the most marked innervation from the VTA. A more widespread presence of DA in other cortices of rodents becomes progressively more evident in carnivores and primates. Most but not all projections are unilateral. Some neurons project to more than one area in mesodiencephalic, limbic and cortical systems. The majority of these fibers ascend in the MFB. Most areas receiving a projection from the VTA (DA or non-DA) project back to the VTA. The septohippocampal complex in particular and the limbic system in general provide quantitatively much less feedback than other areas. The role of the VTA as a mediator of dialogue with the frontostriatal and limbic/extrapyramidal system is discussed under the theme of circuit systems. The large convergence of afferents to certain VTA projection areas (prefrontal, entorhinal cortices, lateral septum, central amygdala, habenula and accumbens) is discussed under the theme of convergence systems.(ABSTRACT TRUNCATED AT 400 WORDS)

Catecholaminergic innervation of the septal area in man: immunocytochemical study using TH and DBH antibodies

The catecholaminergic innervation of the human septal area and closely related structures has been visualized by using tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) as immunocytochemical markers. TH-like immunoreactivity with no corresponding DBH labelling was considered to be indicative of dopaminergic fibers. Catecholaminergic innervation offered the following similarities to that of rodents: moderate innervation in the medial septal division, with predominant DBH immunolabelling; dense dopaminergic innervation in the lateral septal nuclei, organized in a laminar pattern; presence of dopaminergic pericellular arrangements in the dorsal septum and bed n. of the stria terminalis; clustering of dopaminergic terminals in n. accumbens associated with a medioventral zone of DBH-like immunoreactive fibers; close overlap between dopaminergic fields and acetylcholinesterase-reactive zones in both the lateral septum and the n. of the stria terminalis. Differences with the catecholaminergic septal innervation of rodents consisted of general caudal extension of the dopaminergic fields, possibly accounted for by the vertical stretching and caudal displacement of the septal nuclei in man; complementary lateromedial topography of dopaminergic and DBH-immunoreactive inputs in the n. of the stria terminalis as opposed to their dorsoventral organization in rodents; presence of TH-immunolabelled cell group in the anterior olfactory nucleus and parolfactory cortex, which seems specific for primates. Precise topographical mapping of the catecholaminergic structures in this central region of the limbic forebrain seems to be a prerequisite for accurate tissue sampling in the biochemical investigations of pathological cases and should help in the interpretation of aminergic dysfunction in a variety of human diseases.

Distribution of central cholinergic neurons in the baboon (Papio papio). II. A topographic atlas correlated with catecholamine neurons

The topographic distribution of central cholinergic and catecholaminergic neurons has been investigated in the baboon (Papio papio). The perikarya were mapped on an atlas through the brain and spinal cord employing sections processed for acetylcholinesterase (AChE) pharmacohistochemistry coupled with choline acetyltransferase (ChAT) immunohistochemistry or aqueous catecholamine-fluorescence histochemistry. Compared with subprimates, there is a remarkable increase in the volume occupied by and the number of cholinergic cells contained in the nucleus basalis and nucleus tegmenti pedunculopontinus (subnucleus compacta). The elaboration of these parts of the cholinergic system is accompanied by a large extension of catecholaminergic cell groups in the midbrain (groups A8-A10), particularly the substantia nigra (pars compacta), and in the dorsolateral pontine tegmentum (A5-A7 complex). Although cholinergic and catecholaminergic soma generally occupy distinctly different regions of the brain, a close apposition of cholinergic and noradrenergic neurons occurs in the dorsolateral pontine tegmentum. In the peripeduncular region ChAT-positive cells and green fluorescent neurons of the A6-A7 complex form parallel lines and do not intermingle as has previously been demonstrated in the cat. Two distribution patterns, aggregated or disseminated, are another common feature of central cholinergic and catecholaminergic perikarya. The cholinergic neurons in the nucleus tegmenti pedunculopontinus and the catecholaminergic neurons in A6-A7 complex display both patterns. This comparative study of three transmitter systems in the baboon suggests that the cholinergic as well as the catecholaminergic neurons that give rise to ascending telencephalic and dorsal diencephalic projections undergo phylogenetic development in terms of cell number and nuclear volume.

Features of brain atrophy in Parkinson's disease. A CT scan study

Multiple parameters for brain volume and mass were studied in 85 parkinsonian patients and in 149 normal controls aged 24 to 84 using CT scanning. In controls there was reduction in brain substance with advancing age. Increased brain atrophy in patients with Parkinson's disease (PD) was mainly observed in the younger age group of 24 to 49. This included parameters evaluating the size of the lateral and third ventricles (P less than 0.05 and P less than 0.01 respectively) and the size of the subarachnoid space in the frontal interhemispheric and Sylvian fissures (P less than 0.005 and P less than 0.01). With computed canonical correlation analysis a formula was obtained which expressed the tendency of the atrophic process in PD to involve the areas surrounding the third ventricle and the mesial aspect of the frontal lobes more than during normal aging.

The locus coeruleus and its possible role in ageing and degenerative disease of the human central nervous system

The central noradrenergic pathways with the mammalian brain are principally based on that group of nerve cells within the reticular substance of the upper pons known as the locus coeruleus. The physiological role of these nerve cells appears to be one of maintaining homeostasis within the central nervous system, whatever adverse conditions prevail in the rest of the body, through governing the flow of blood through, and degree of water permeability of, the capillary bed. The extensive ramifications of these noradrenergic terminals mean that the atrophy and loss of nerve cells from locus coeruleus that occurs in old age, and especially so in degenerative diseases of the central nervous system such as Alzheimer's disease and other conditions, will have widespread repercussions for brain function. The chain of physiological disturbances set up as a result of this cell loss may mean a progressive failure of homeostasis within the brain, which in the extreme may culminate in that pattern of mental breakdown which is usually termed dementia.

Tyrosine hydroxylase and methionine-enkephalin in the human mesencephalon. Immunocytochemical localization and relationships

The immunocytochemical localization of tyrosine hydroxylase (TH) and methionine-enkephalin (met-enkephalin) was determined at two representative caudal and rostral levels of the human mesencephalon. Four main groups of catecholaminergic neurons were delineated, situated in the substantia nigra and the lateral, ventromedial and dorsomedial tegmentum, extending over several cytoarchitectonic divisions. They matched fairly well the dopaminergic cell groups described in monkey midbrain. TH-like immunoreactivity and neuromelanin were closely related in neurons of substantia nigra, but less so in the other groups. A widespread met-enkephalinergic innervation was observed in most areas containing catecholaminergic neurons. It followed a characteristic pattern: homogeneous and very dense in the lateral and posterior portions of substantia nigra; patchy and less dense in the other areas, the medio-ventral and periaqueductal gray being only sparsely innervated, in contrast to observations in rodents. Dopaminergic cell bodies surrounded by met-enkephalinergic varicosities were seen in most groups, particularly in the lateral substantia nigra and medioventral tegmentum. The topography of met-enkephali-like immunoreactive terminals in the substantia nigra was reminiscent of the distribution of neostriatal and pallidal afferents.

Human brainstem catecholamine neuronal anatomy as indicated by immunocytochemistry with antibodies to tyrosine hydroxylase

Immunocytochemistry based on antibodies to tyrosine hydroxylase is used to identify catecholaminergic neurons in the human brain stem. An atlas is provided and the distribution of structures compared with that in other animals and with biochemical and catecholamine fluorescent data from humans. Broad agreement of results increases the confidence with which tyrosine hydroxylase-like immunoreactivity can be used to trace catecholaminergic pathways in human postmortem material. As compared to most studies of other animals there are striking increases in populations of upper pontine and mesencephalic catecholaminergic neurons in the human. Distinct cytoarchitectonic features, consistent differences in tyrosine hydroxylase immunoreactive staining intensity and regional variations in substance P innervation indicate complexity within the substantia nigra. Human catecholaminergic neurons are prominent in the midline of the ventral tegmentum and the upper parts of the central tegmental tracts. A bundle of tyrosine hydroxylase-immunoreactive axons runs between the latter regions and a cluster of smaller catecholaminergic neurons which lie in the oblique band of axons joining ventrolateral and dorsomedial medullary catecholaminergic groups. There are more catecholaminergic neurons within and closely related to the superior cerebellar peduncles than have been described in other species. Anatomically, the central compact nucleus of the locus coeruleus appears to be related to several nearby catecholaminergic cell groups. The data provided are being used as a basis for neuropathologic studies of human neurological diseases.

Microtopography of methionine-enkephalin, dopamine and noradrenaline in the ventral mesencephalon of human control and Parkinsonian brains

The topographical distributions of Met-enkephalin, dopamine and noradrenaline were determined in serial frontal sections of human substantia nigra (pars compacta and pars reticulata) and ventral tegmental area. Met-enkephalin was identified by Biogel and thin layer chromatography and assayed by a specific radioimmunoassay. In the substantia nigra (pars compacta and pars reticulata), the levels of Met-enkephalin increased progressively from the rostral to the caudal part of the structure. This pattern closely resembled that of dopamine levels, particularly in the pars compacta. Noradrenaline levels in the substantia nigra and those of Met-enkephalin, dopamine, and noradrenaline in the ventral tegmental area, exhibited only limited fluctuations from the anterior to the posterior part of each structure. Highly significant decreases in Met-enkephalin, dopamine and noradrenaline levels were observed in the substantia nigra and ventral tegmental area of Parkinsonian brains. This observation, together with the close topographical association of dopamine and Met-enkephalin in the substantia nigra, further supports the likely existence of important functional relationships between dopaminergic and enkephalinergic neurons in the human brain.

Relatively high levels of dopamine in nucleus accumbens of levodopa treated patients with Parkinson's disease

The dopamine levels were found to be low in the putamen and relatively high in the nucleus accumbens in two Parkinson disease patients treated with levodopa up to the time of their deaths. Tyrosine hydroxylase immunocytochemistry revealed a severe degeneration of the nigro-striatal dopamine neuronal system in both postmortem brains. The relatively high dopamine levels in the nucleus accumbens may be responsible for the occurrence of dyskinesias.

Microtopography of tyrosine hydroxylase, glutamic acid decarboxylase, and choline acetyltransferase in the substantia nigra and ventral tegmental area of control and Parkinsonian brains

Tyrosine hydroxylase (TH), glutamic acid decarboxylase (GAD), and choline acetyl transferase (CAT) were used as markers for catecholamine, gamma-aminobutyric acid, and acetylcholine containing neurons in human mesencephalon. Their rostrocaudal, mediolateral, and dorsoventral distribution was investigated within the substantia nigra pars compacta (SNC) and pars reticulata (SNR) and in the ventral tegmental area (VTA). TH activity was highest in the caudal, medial, and ventral SNC and in the middle of VTA medio-ventrally. The enzyme activity in SNR was low and uniformly distributed. In SNC as well as SNR, GAD activity was high and greater laterally and in the middle of the rostro-caudal extent. No particular pattern of distribution was observed in VTA. an area with low GAD content. In the substantia nigra, CAT activity was low. A characteristic medio-ventral distribution with a peak of high enzyme activity in the middle of the rostrocaudal extent was observed. In VTA, enzyme levels were high and also concentrated medio-ventrally and in the middle of the area. In parkinsonian brains, the distribution of TH was uniformly affected throughout the rostro-caudal extent. In VTA the enzyme activity was not as reduced as in SNC and SNR; the CAT pattern was only disrupted in a very localized part of SNC but not in SNR and VTA. In all three areas, GAD activity was reduced to a uniformly low distribution.

Immunocytochemical localization of tyrosine hydroxylase in the human fetal nervous system

The peroxidase-antiperoxidase (PAP) technique is used to determine the cellular localization of tyrosine hydroxylase in the human fetal nervous system. Antiserum to trypsin-treated tyrosine hydroxylase from the bovine adrenal medulla can be detected immunocytochemically in peripheral sympathetic neurons in the 8-mm (5-week) fetus, but can not be detected in the central nervous system until later stages of development. The cytological features and distribution of the neuronal perikarya and processes labeled for the enzyme are similar to those of the catecholaminergic neurons previously identified by histofluorescence. These findings indicate that specific neurons in the human fetus have at least one of the enzymes necessary for the biosynthesis of catecholamines and that cross-species reactivity exists between antiserum produced to the bovine tyrosine hydroxylase and human tissues.