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

Distribution of the catecholaminergic neurons in the central nervous system of human embryos and fetuses

The catecholaminergic cell groups in the human brain, denominated from A1 to A17, display some striking anatomical differences with those described in the rodent. These differences are essentially observed in the extent of the dopaminergic neurons and especially their axonal fields in the telencephalon. Immunocytochemistry for tyrosine-hydroxylase and dopamine-ss-hydroxylase allowed the visualization of the precocious human catecholaminergic groups as early as 4.5 postovulatory weeks. Maps of tyrosine-hydroxylase positive neurons generated in the different rhombomeres, midbrain, and prosomeres are shown following the prosomeric model introduced by Puelles and Rubenstein [(1993) Trends Neurosci. 16:472-476]. Such a description is convenient to compare catecholaminergic systems in different mammalian species and provide clear anatomical landmarks of the embryonic substantia nigra (midbrain and prosomeres 1 and 2), that are necessary for transplantation of neural tissue in Parkinson's disease. The development and early specification of the dopaminergic neurons expressing calbindin D28K phenotype in the substantia nigra and in the ventral tegmental area are described. The catecholaminergic axons enter the anlage of the cerebral cortex just after the formation of the cortical plate, from 7 postovulatory weeks on. They invade the subplate layer where they wait for 4 weeks before penetrating the cortical plate. At midgestation, the different areas and layers of the frontal cerebral wall are invaded by the catecholaminergic axons, before the layering of the cortex is completed, in a pattern of fiber distribution similar to that described in the adult human brain. The early pattern of development of the catecholamine systems appeared to be phylogenetically well preserved in mammals, but specific features emerging during the differentiation period are unique to humans.

Immunocytochemical localization of the dopamine transporter in human brain

The dopamine transporter (DAT) was localized in normal human brain tissue by light microscopic immunocytochemistry by using highly specific monoclonal antibodies. Regional distribution of DAT was found in areas with established dopaminergic circuitry, e.g., mesostriatal, mesolimbic, and mesocortical pathways. Mesencephalic DAT-immunoreactivity was enriched in the dendrites and cell bodies of neurons in the substantia nigra pars compacta and ventral tegmental area. Staining in the striatum and nucleus accumbens was dense and heterogeneous. Mesocortical DAT immunoreactivity in motor, premotor, anterior cingulate, prefrontal, entorhinal/perirhinal, insular, and visual cortices was detected in scattered varicose and a few nonvaricose fibers. Varicose fibers were relatively enriched in the basolateral and central subnuclei of amygdala, with sparser fibers in lateral and basomedial subnuclei. Double-labeling studies combining DAT and tyrosine hydroxylase (TH) immunostaining in the ventral mesencephalon showed two subpopulations of dopaminergic neurons differentiated by the presence or absence of DAT-immunoreactivity in the A9 and A10 cell groups. In other dopaminergic cell groups (All, A13-A15), TH-positive hypothalamic neurons showed no detectable DAT-immunoreactivity. However, fine DAT-immunoreactive axons were scattered throughout the hypothalamus, particularly concentrated along the medial border, with more coarse axons present along the lateral border. These findings demonstrate that most mesotelencephalic dopamine neurons of human brain express high levels of DAT throughout their entire somatodendritic and axonal domains, whereas a smaller subpopulation of mesencephalic dopamine cells and all hypothalamic dopamine cell groups examined express little or no DAT. These data indicate that different subpopulations of dopaminergic neurons use different mechanisms to regulate their extracellular dopamine levels.

Aromatic L-amino acid decarboxylase- and tyrosine hydroxylase-immunohistochemistry in the adult human hypothalamus

The distribution of cell bodies immunoreactive for tyrosine hydroxylase and aromatic L-amino acid decarboxylase was studied in the adult human hypothalamus. Many neurons in the posterior (A11) and caudal dorsal hypothalamic areas (A13) as well as in the arcuate (A12) and periventricular (A14) zone were immunoreactive for the two enzymes, suggesting that they were dopaminergic. Numerous tyrosine hydroxylase-immunoreactive neurons, which were not immunoreactive for aromatic L-amino acid decarboxylase, could be seen in the paraventricular, supraoptic and accessory nuclei (A15) as well as in the rostral dorsal hypothalamic area. These were considered to be non-dopaminergic. Conversely, large numbers of small neurons immunoreactive for aromatic L-amino acid decarboxylase but not for tyrosine hydroxylase, were identified in the premammillary nucleus (D8), zona incerta (D10), lateral hypothalamic area (D11), anterior portion of the dorsomedial nucleus (D12), suprachiasmatic nucleus (D13), medial preoptic area and bed nucleus of the stria terminalis (D14). In the human hypothalamus, besides dopaminergic cell bodies, there exists a large number of tyrosine hydroxylase-only and aromatic L-amino acid decarboxylase-only neurons, whose physiological roles remain to be determined.

Loss of catecholaminergic neurons in the medullary reticular formation in myotonic dystrophy

OBJECTIVE

To clarify the possible relation between the extent of involvement of catecholaminergic neurons and the presence of alveolar hypoventilation in patients with myotonic dystrophy (MyD).

BACKGROUND

Respiratory insufficiency has been reported frequently in MyD patients. Recent data support the hypothesis that this respiratory failure results from a primary dysfunction of the CNS.

METHODS

The authors performed a quantitative immunoreactive study of tyrosine hydroxylase immunoreactive (TH+) neurons linked to hypoventilation in the dorsal central medullary nucleus (DCMN), the ventral central medullary nucleus (VCMN), and the subtrigeminal medullary nucleus (SMN)--where the autonomic respiratory center is thought to be located--in eight MyD patients and in 10 age-matched control subjects. Alveolar hypoventilation of the central type was present in three of the MyD patients but not in the remaining MyD patients or the control subjects.

RESULTS

The densities of TH+ neurons of the DCMN, the VCMN, and the SMN in MyD patients with hypoventilation were significantly lower than in those without hypoventilation (p < 0.02, p < 0.01, and p < 0.01, respectively) and control subjects (p < 0.01, p < 0.01, and p < 0.01, respectively).

CONCLUSIONS

These data suggest that the loss of TH+ neurons of the DCMN, the VCMN, and the SMN is associated with the presence of hypoventilation in MyD and may be an important feature of MyD.

Do all of human midbrain tyrosine hydroxylase neurons synthesize dopamine?

We examined whether all of human midbrain tyrosine hydroxylase (TH) neurons substantially synthesize dopamine (DA) using dual labeling immunohistochemical technique of TH and aromatic L-amino acid decarboxylase (AADC). In the substantia nigra, besides many neurons doubly stained for TH and AADC, neurons stained only for TH and only for AADC (D-neurons [C.B. Jaeger, D.A. Ruggiero, V.R. Albert, T.H. Joh, D.J. Reis, Immunocytochemical localization of aromatic l-amino acid decarboxylase, in: A. Björklund, T. Hökfelt (Eds.), Handbook of Chemical Neuroanatomy, Classical Transmitters in the CNS, Vol. 2, Part 1, Elsevier, Amsterdam, 1984, pp. 387-408.]) were identified. In the ventral tegmental area, dually labeled neurons and TH-only-positive neurons were found. It is indicated that the number of midbrain TH neurons does not reflect the exact number of DA neurons.

Chemoarchitecture of the primate dorsal raphe nucleus

The dorsal raphe nucleus (DR) harbours the largest single collection of serotonin (5-HT)-containing neurons in the brain but also comprises other types of chemospecific neurons. The aim of the present study was to characterise morphologically and immunohistochemically the DR in the squirrel monkey (Saimiri sciureus). The morphology of the DR 5-HT-immunoreactive (ir) neurons was analysed and their distribution compared to that of neurons displaying immunoreactivity for either tyrosine hydroxylase (TH), gamma-aminobutyric acid (GABA), substance P (SP), calbindin-D28k (CB), calretinin (CR) or parvalbumin (PV). The 5-HT-ir neurons were distributed in a highly heterogeneous manner throughout the rostrocaudal extent of the DR. The morphology and density of the 5-HT neurons were found to vary significantly in the major subdivisions of the primate DR, that is, the median, ventral, dorsal, ventrolateral, lateral and caudal subnuclei. Numerous SP-, GABA- and PV-ir neurons occurred in all six subnuclei of the DR. The distribution of SP-ir neurons was largely in register with that of 5-HT-ir neurons. Neurons expressing the other neuronal markers (TH, CB, CR) were not present in all six DR subnuclei and their distribution was either complementary to, or in register with, that of 5-HT-ir neurons. The median subnucleus was unique because it contained all the different types of chemospecific neurons. This study has revealed that the primate DR is chemically highly heterogeneous, a finding that may explain the multifarious influence that this nucleus exerts upon various forebrain structures.

Early neuromeric distribution of tyrosine-hydroxylase-immunoreactive neurons in human embryos

A segmental mapping of brain tyrosine-hydroxylase-immunoreactive (TH-IR) neurons in human embryos between 4.5 and 6 weeks of gestation locates with novel precision the dorsoventral and anteroposterior topography of the catecholamine-synthetizing primordia relative to neuromeric units. The data support the following conclusions. (1) All transverse sectors of the brain (prosomeres in the forebrain, midbrain, rhombomeres in the hindbrain, spinal cord) produce TH-IR neuronal populations. (2) Each segment shows peculiarities in its contribution to the catecholamine system, but there are some overall regularities, which reflect that some TH-IR populations develop similarly in different segments. (3) Dorsoventral topology of the TH-IR neurons indicates that at least four separate longitudinal zones (in the floor and basal plates and twice in the alar plate) found across most segments are capable of producing the TH-IR phenotype. (4) Basal plate TH-IR neurons tend to migrate intrasegmentally to a ventrolateral superficial position, although some remain periventricular; those in the brainstem are related to motoneurons of the oculomotor and branchiomotor nuclei. (5) Some alar TH-IR populations migrate superficially within the segmental boundaries. (6) Most catecholaminergic anatomical entities are formed as fusions of smaller segmental components, each of which show similar histogenetic patterns. A nomenclature is proposed that partly adheres to previous terminology but introduces the distinction of embryologically different cell populations and unifies longitudinally analogous entities. Such a model, as presented in the present study, is convenient for resolving problems of homology of the catecholamine system across the diversity of vertebrate forms.

Catecholamine neurons alteration in the brainstem of sudden infant death syndrome victims

BACKGROUND

Sudden infant death syndrome (SIDS) is a leading cause of postneonatal infant death. The pathogenesis of sudden death is still unknown, but an abnormality in the central nervous regulation of breathing during sleep has been suggested.

OBJECTIVE

The aim of study is to confirm the brainstem disorder of SIDS victims. In order to do this, it is necessary to investigate the alterations of brain neurotransmitter systems thought to be involved in respiratory control.

DESIGN

Neuropathologic study performed on the brainstem of SIDS victims.

SUBJECT/METHODS

The disorders of catecholaminergic systems in 22 SIDS victims were examined on the substantia nigra in the midbrain, locus coeruleus in the pons, vagal nuclei, and area reticularis superficialis ventrolateralis with the immunohistochemical method. Immunoperoxidase staining was performed with the antityrosine hydroxylase (TH) and the glial fibrillary acidic protein antibodies. Immunoreactivity was compared with 13 age-matched control infants. For statistical analysis, the chi 2 test and the Student's t test were performed.

RESULTS

The main finding was diminished TH immunoreactivity in the vagal nuclei and area reticularis superficialis ventrolateralis of SIDS victims, suggesting that adrenaline and noradrenaline neurons are altered in SIDS. In addition, this decrease in TH was closely correlated with brainstem gliosis.

CONCLUSION

These catecholaminergic changes may be caused by chronic hypoxia or ischemia, and also may underlie alterations in respiratory and cardiovascular control in sleep.

Three-dimensional mapping of norepinephrine and serotonin in human thalamus

Detailed quantitative information on catecholamines and 5-hydroxytryptamine (serotonin) in the human thalamus is much needed because of increasing interest in norepinephrine and serotonin as modulators of thalamic behavioral state control and overall information processing. This study provides three-dimensional distribution patterns of these monoamines in postmortem thalami from 13 normal subjects (no known neurological or psychiatric histories). The patterns come from a relatively fine-grained grid mapping procedure on successive coronal sections. Samples were analyzed by high performance liquid chromatography with electrochemical detection. The highest endogenous concentrations of norepinephrine are found in a ventromedial core that includes a number of the medial and intralaminar sub-nuclei but extends only slightly into the sensory regions of the lateral tier. The posterior portion of the thalamus, the pulvinar, contains low levels of norepinephrine. The distribution of 5-hydroxytryptamine is quite similar to that of norepinephrine in the rostral two-thirds of thalamus; however, in the pulvinar region, levels of serotonin are considerably increased and differ markedly between individual thalami. The study provides the first definitive mapping of serotonin levels in human thalamus. Consistent with many animal studies, there is no evidence for major dopaminergic innervation of human thalamus. By emphasizing the pattern distribution of the monoamines rather than the absolute values, it can be shown that the ambiguities of postmortem degradation frequently associated with biochemical assays are largely avoided. The terminal field distribution of norepinephrine is an essentially constant neurochemical signature in all thalami examined. The utility of the biochemical grid mapping procedure may be especially significant in terms of matching with data from functional neuroimaging techniques.

Mesopontine organization of cholinergic and catecholaminergic cell groups in the normal and narcoleptic dog

Canine narcolepsy is a unique experimental model of a human sleep disorder characterized by excessive daytime sleepiness and cataplexy. There is a consensus recognition of an imbalance between cholinergic and catecholaminergic systems in narcolepsy although the underlying mechanisms remain poorly understood. Possible substrates could be an abnormal organization, numbers and/or ratio of cholinergic to catecholaminergic cells in the brain of narcoleptic dogs. Therefore, we sought to characterize the corresponding neuronal populations in normal and narcoleptic dogs (Doberman Pinscher) by using choline acetyltransferase (ChAT), nicotinamide adenosine dinucleotide phosphate (NADPH)-diaphorase, tyrosine hydroxylase (TH), and dopamine beta-hydroxylase (DBH). Cholinergic cell groups were found in an area extending from the central to the gigantocellular tegmental field and the periventricular gray corresponding to the pedunculopontine tegmental nucleus (PPT), the laterodorsal tegmental nucleus (LDT), and the parabrachial nucleus. An almost perfect co-localization of ChAT and NADPH-diaphorase was also observed. Catecholaminergic cell groups detected included the ventral tegmental area, the substantia nigra, and the locus coeruleus nucleus (LC). The anatomical distribution of catecholaminergic neurons was unusual in the dog in two important aspects: i) TH- and/or DBH-immunoreactive neurons of the LC were found almost exclusively in the reticular formation and not within the periventricular gray, ii) very few, if any TH-positive neurons were found in the central gray and dorsal raphe. Quantitative analysis did not reveal any significant differences in the organization and the number of cells identified in the LDT, PPT, and LC of normal and narcoleptic dogs. Moreover, the cholinergic to catecholaminergic ratio was found identical in the two groups. In conclusion, the present results do not support the hypothesis that the neurochemical imbalance in narcolepsy could result from abnormal organization, numbers, or ratio of the corresponding neuronal populations.

Distribution of alpha 2-adrenoceptors in the human locus coeruleus

Recent reports of specific topographic patterns of cell loss in the locus coeruleus (LC) in psychiatric and neurologic disorders underscores the need for detailed neurochemical analyses of this cell group. In this study, the anatomical distribution of alpha 2-adrenoceptors and its relationship to the distribution of noradrenergic neurons in the human LC was studied. Quantitative autoradiography was used to assess the binding of [125I]p-iodoclonidine ([125I]PIC) to alpha 2-adrenoceptors coordinately with counts of neuromelanin-containing cells in tissue sections cryocut at 10-13 levels along the rostrocaudal axis of the LC. Pontine brain tissue was obtained postmortem from 7 subjects dying of natural or accidental causes, ranging in age from 26 to 78 years. Both the binding of [125I]PIC and number of neuromelanin-containing cells were differentially distributed along the LC axis (P < 0.01) with almost identical topographical patterns. The highest concentration of binding and the greatest number of neuromelanin-containing cells per section occurred near the middle portion of the nucleus. There was a significant correlation between the number of neuromelanin-containing cells per section and the specific binding of [125I]PIC at any particular level of the LC (r2 = 0.56; P < 0.0001). The highest and lowest amounts of [125I]PIC binding in the LC were observed in the youngest and oldest subjects, respectively, and this trend was parallelled by a significant negative correlation between the number of neuromelanin-containing cells at a given level and age (r2 = 0.85; P < 0.003). The uneven distribution of alpha 2-adrenoceptors in the LC demonstrates the importance of anatomical specificity when performing quantitative studies of LC protein chemistry in psychiatric and neurologic disorders.

Midbrain dopaminergic neurons in the mouse: computer-assisted mapping

The dopaminergic (DA) neurons in the midbrain play a role in cognition, affect and movement. The purpose of the present study was to map and quantify the number of DA neurons in the midbrain, within the nuclei that constitute cell groups A8, A9 and A10, in the mouse. Two strains of mice were used; the C57BL/6 strain was chosen because it is commonly used in neurobiological studies, and the FVB/N strain was chosen because it is used frequently in transgenic studies. DA neurons were identified, in every fifth 20-microns-thick coronal section, using an antibody against tyrosine hydroxylase. Cell locations were entered into a computer imaging system. The FVB/N strain has 42% more midbrain DA neurons than the C57BL/6 strain; on one side of the brain there were 15,135 +/- 356 neurons (mean +/- S.E.M.) in the FVB/N strain, and 10,645 +/- 315 neurons in the C57BL/6 strain. In both strains, approximately 11% of the neurons were located in nucleus A8 (the DA neurons in the retrorubral field), 38% in nucleus A9 (the DA neurons in the substantia nigra pars compacta, pars reticulata, and pars lateralis), and 51% in nucleus A10 (the DA neurons in midline regions such as the ventral tegmental area, central linear nucleus, and interfascicular nucleus). The number of midbrain DA cells, and their distribution within the three nuclear groups, is discussed with respect to findings in other species.

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.

Immunocytochemical distribution of catecholamine-synthesizing neurons in the hypothalamus and pituitary gland of pigs: tyrosine hydroxylase and dopamine-beta-hydroxylase

This study describes the distribution of catecholaminergic neurons in the hypothalamus and the pituitary gland of the domestic pig, Sus scrofa, an animal that is widely used as an experimental model of human physiology in addition to its worldwide agricultural importance. Hypothalamic catecholamine neurons were identified by immunocytochemical staining for the presence of the catecholamine synthesizing enzymes, tyrosine hydroxylase and dopamine-beta-hydroxylase. Tyrosine hydroxylase-immunoreactive perikarya were observed in the periventricular region throughout the extent of the third ventricle, the anterior and retrochiasmatic divisions of the supraoptic nucleus, the suprachiasmatic nucleus, the ventral and dorsolateral regions of the paraventricular nucleus and adjacent dorsal hypothalamus, the ventrolateral arcuate nucleus, and the posterior hypothalamus. Perikarya ranged from parvicellular (10-15 microns) to magnocellular (25-50 microns) and were of multiple shapes (rounded, fusiform, triangular, or multipolar) and generally had two to five processes with branched arborization. No dopamine-beta-hydroxylase immunoreactive perikarya were observed within the hypothalamus or in the adjacent basal forebrain structures. Both tyrosine hydroxylase- and dopamine-beta-hydroxylase-immunoreactive fibers and punctate varicosities were observed throughout areas containing tyrosine hydroxylase perikarya, but dopamine-beta-hydroxylase immunoreactivity was very sparse within the median eminence. Within the pituitary gland, only tyrosine hydroxylase fibers, and not dopamine-beta-hydroxylase immunoreactive fibers, were located throughout the neurohypophyseal tract and within the posterior pituitary in both pars intermedia and pars nervosa regions. Generally, the location and patterns of both catecholamine-synthesizing enzymes were similar to those reported for other mammalian species except for the absence of the A15 dorsal group and the very sparse dopamine-beta-hydroxylase immunoreactive fibers and varicosities in the median eminence in the pig. These findings provide an initial framework for elucidating behavioral and neuroendocrine species differences with regard to catecholamine neurotransmitters.

Three-dimensional distribution of [3H]quinuclidinyl benzilate binding to muscarinic cholinergic receptors in the developing human brainstem

Acetylcholine has been implicated in brainstem mechanisms of cardiac and ventilatory control, arousal, rapid eye movement (REM) sleep, and cranial nerve motor activity. Virtually nothing is known about the developmental profiles of cholinergic perikarya, fibers, terminals, and/or receptors in the brainstems of human fetuses and infants. This study provides baseline information about the quantitative distribution of muscarinic cholinergic receptors in fetal and infant brainstems. Brainstem sections were analyzed from 6 fetuses (median age: 21.5 postconceptional weeks), 4 premature infants (median age: 26 postconceptional weeks), and 11 infants (median age: 53 postconceptional weeks). One child and three adult brainstems were examined as indices of maturity for comparison. The postmortem interval in all cases was less than or equal to 24 hours (median: 10 hours). Muscarinic receptors were localized by autoradiographic methods with the radiolabeled antagonist [3H]quinuclidinyl benzilate ([3H]QNB). Computer-based methods permitted quantitation of [3H]QNB binding in specific nuclei and three-dimensional reconstructions of binding patterns. By midgestation, muscarinic cholinergic receptor binding is already present and regionally distributed, with the highest binding levels in the interpeduncular nucleus, inferior colliculus, griseum pontis, nucleus of the solitary tract, motor cranial nerve nuclei, and reticular formation. During the last half of gestation, [3H]QNB binding decreases in most, but not all of the nuclei sampled. The most substantial decline occurs in the reticular formation of the medulla and pons, a change that is not fully explained by progressive myelination and lipid quenching. Binding levels remain essentially constant in the inferior olive and griseum pontis. Around the time of birth or shortly thereafter, the relative distribution of binding becomes similar to that in the adult, with the highest levels in the interpeduncular nucleus and griseum pontis, although binding levels are higher overall in the infant. In the rostral pontine reticular formation, paramedian bands of high muscarinic binding are present which do not correspond to a cytoarchitectonically defined nucleus. By analogy to animal studies, these bands may comprise a major cholinoreceptive region of the human rostral pontine reticular formation involved in REM sleep. In the human interpeduncular nucleus in all age periods examined, muscarinic binding localizes to the lateral portions bilaterally, indicative of a heterogeneous chemoarchitecture. Muscarinic binding is high in the arcuate nucleus, a component of the putative respiratory chemosensitive fields along the ventral surface of the infant medulla. This observation is consistent with the known effects of muscarinic agents on chemosensitivity and ventilatory responses applied to the ventral medullary surface in animal models. The nonuniform distribution of muscarinic binding in the caudorostral plane in individual brainstem nuclei, as illustrated by three-dimensional reconstructions, underscores the need for rigorous sampling at precisely matched levels in quantitative studies. This study provides basic information toward understanding the neurochemical basis of brainstem disorders involving dysfunction of autonomic and ventilatory control, arousal, and REM sleep in preterm and full-term newborns and infants and for developing cholinergic drugs for such disorders in the pediatric population.

Regional distribution of substance P binding sites in the brainstem of the human newborn

The distribution of [3H]substance P ([3H]SP) binding sites in the brainstem of the human newborn was investigated in eleven cases (aged 1 h to 6 months) by in vitro quantitative receptor autoradiography. The binding of [3H]SP to newborn brainstem tissue was found to be saturable (for the eight cases examined, Kd and Bmax (M +/- S.E.M.) were 0.29 +/- 0.03 nM and 206 +/- 21 fmol/mg tissue, respectively). Competition studies showed unlabeled SP to be the most potent peptide for displacing [3H]SP binding from tissue sections. The desaturating effect of GTP on the specific binding of [3H]SP was also investigated, but was not found to be significant. Autoradiographic analysis showed that the neurokinin-1 (NK-1)/SP binding sites were widely but unevenly distributed, and that they varied with age. The highest densities of (NK-1)/SP binding sites were observed in the locus coeruleus, olivaris inferior nuclei, raphe magnus and obscurus nuclei, while low to moderate densities were observed in other brainstem structures. These findings support the idea that SP is involved in cardiovascular regulation, and that it may interact with the catecholaminergic and/or serotonergic system.

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.

Development of the catecholamine neurons in human embryos and fetuses, with special emphasis on the innervation of the cerebral cortex

The cathecholaminergic (CA) systems have been described as appearing early in the development of the mammalian central nervous system (CNS), but their exact distribution in humans has been studied only following gestational week (g.w.) 13. Furthermore, it is not known when CA fibers initially penetrate the developing cerebral cortex. In this study, the CA cells groups and fibers are described in the human central nervous system from 6 to 13 g.w. as revealed with immunocytochemical techniques, with antibodies raised against three synthetic enzymes of the catecholamine (CA) pathway: tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), and phenylethanolamine-N-methyltransferase (PNMT). At 6 g.w., TH-like immunoreactive (TH-IR) cell groups were widespread through the caudorostral extension of the CNS corresponding to the different dopaminergic mesencephalic and hypothalamic groups. Noradrenergic groups also were labeled in the medulla oblongata and in the locus coeruleus as well as in other areas in the pons. Additional TH-IR cell groups might represent a transient developmental expression of TH similar to that observed in the rat. DBH immunoreactivity labeled primarily the noradrenergic pontic cell groups and, to a lesser extent, groups located in the medulla oblongata. Rare PNMT-IR neurons were detected in the medulla oblongata only at 13 g.w. The main CA bundles described in the adult were also observed in human embryos and fetuses. At 6 g.w., TH-IR pathways extended caudorostrally within the central tegmental tract and the dorsal tegmental bundle, the latter merging with the dopaminergic mesotelencephalic pathway giving rise to the medial forebrain bundle in the basal forebrain. At 7-8 g.w., TH-IR fibers extended to the basal ganglia and the telencephalic wall. The first TH-IR and, to a much lesser extent, DBH-IR fibers penetrated the frontal lateral cortical anlage through the intermediate zone and sparsely through the marginal zone but not through the thin cortical plate. A second stream entered the telencephalic anlage frontomedially, ventral to the septal area. At 11 g.w., numerous TH-IR fibers invaded the subplate layer, but they penetrated the cortical plate only at 13 g.w. At that time, TH-IR and DBH-IR fibers had reached the occipital cortex in a rostrocaudal gradient. The appearance of well-organized CA system already in embryonic stages in humans could be of great importance for normal shaping of the nervous system as well as for development of cortical circuitry.

Distribution of secretoneurin-like immunoreactivity in comparison with that of substance P in the human brain stem

Secretoneurin is a peptide of 33 amino acids generated in the brain by proteolytic processing of secretogranin II which is a member of the chromogranin/secretogranin family. The distribution of this newly characterized peptide was investigated by immunocytochemistry in the human brain stem. The staining pattern of secretoneurin-like immunoreactivity was compared with that of substance P in adjacent sections. Secretoneurin-like immunoreactivity appeared mainly in dot- and fiber-like structures with densities varying from low to very high. Only a low number of secretoneurin-immunoreactive perikarya was found. Pericellular staining of both secretoneurin-immunopositive and immunonegative cells was frequently observed in the area of the central gray, in the reticular formation and in the solitary nuclear complex. The medial part of the substantia nigra pars reticulata, the nucleus interpeduncularis, the area of the central gray, the raphe complex and the inferior olive displayed a high density of secretoneurin-like immunoreactivity. Furthermore, a very prominent staining was found in the medial, dorsal and gelatinous subnuclei of the solitary tract and the dorsal motor nucleus of vagus. The substantia gelatinosa of the caudal trigeminal nucleus and spinal cord were also very strongly secretoneurin-immunopositive. The staining patterns of secretoneurin- and substance P-like immunoreactivities were to a certain extent overlapping in several areas. The highest degree of coincidence was found in the substantia gelatinosa. This study demonstrated that secretoneurin is distinctly distributed in the human brain stem. Its distributional pattern indicates a role particularly in the modulation of afferent pain transmission and in the regulation of autonomic functions.

Ultrastructural organization of the noradrenergic innervation of the superficial gray layer of the hamster's superior colliculus

Immunocytochemistry with an antibody-directed tyrosine hydroxylase (TH) was combined with electron microscopy and serial-section analysis to examine the synaptic organization of the catecholaminergic projection to the stratum griseum superficiale (SGS) of the hamster's superior colliculus (SC). A total of 250 TH-immunoreactive profiles within SGS were examined. Of these, 114 (45.6%) made synaptic contacts; 81 (71.1%) were axodendritic, and the remainder (33, 28.9%) were axo-axonic. Serial-section analysis was employed to evaluate the presence or absence of synaptic contacts for 26 profiles. Overall, 19 (73.1%) of the profiles followed through serial sections exhibited synaptic contacts. Double staining of single sections with antibodies directed against TH and dopamine-beta-hydroxylase (D beta H) and examination in the light microscope indicated that virtually all TH-positive fibers also contained D beta H. This indicated that the fibers examined at the electron microscopic level were noradrenergic rather than dopaminergic. These results suggest that norepinephrine may have both pre- and postsynaptic actions in the hamster's SC and that at least some of these effects are mediated by conventional synapses.

Aberrant distribution of tyrosine hydroxylase and substance P in infants with brain-stem infarction

The distribution of tyrosine hydroxylase (TH) and substance P (SP) was examined in the brain-stem of 4 infants with respiratory abnormalities associated with remote brain-stem or cerebellar infarction utilizing immunohistochemical methods. TH-immunoreactive cells and SP-immunoreactive fibers were found in and around the area of the infarction in the tegmentum, in amounts and sites different from that seen in controls. The aberrant localization of SP and TH may represent an altered repair process associated with resolution of the infarction and may be related to abnormal respiratory control or sudden death.

Monoamine oxidase: distribution in the cat brain studied by enzyme- and immunohistochemistry: recent progress

Localization of MAO-containing neurons, fibers and glial cells has been described by recent progress in MAO histochemistry and immunohistochemistry. It does not necessarily correspond to those containing monoamines. MAO-A is demonstrated in many noradrenergic cells, but it is hardly detectable in DA cells. Increase of 5-HT and DA concentration after inhibition of MAO-A indicates the possible existence of MAO-A in such neuronal structures. MAO-A is also undetectable in neurons containing 5-HT, a good substrate for MAO-A. These neurons contain MAO-B. There still remain contradictions to be solved in future. MAO is present in astroglial cells, in which monoamines released in extracellular space may be degraded. In glial cells, MAO may also play a role to regulate concentration of telemethylhistamine and trace amines. Such cells appear to transform MPTP to MPP+, a neurotoxin for nigral DA neurons.

Substance P- and tyrosine hydroxylase-containing neurons in the human dorsal motor nucleus of the vagus nerve

The aim of this study was to provide a comprehensive account of the topography, morphology, and frequencies of the substance P- and tyrosine hydroxylase-containing neurons in the human dorsal motor nucleus of the vagus nerve. The morphology of immunoreactive neurons was studied and the variations of the cell distributions were presented by three-dimensional computer reconstructions. Three types of substance P-like immunoreactive neurons were identified. They were predominantly located in the dorsointermediate, centrointermediate, caudointermediate, and caudal division of the dorsal motor nucleus of the vagus nerve. The morphology of substance P-like immunoreactive neurons varied according to the subnuclei in which they were found. Three types of tyrosine hydroxylase-like immunoreactive neurons were identified, mainly in the periphery of the dorsal motor nucleus of the vagus nerve, including the medial fringe, ventrointermediate, and dorsointermediate subnuclei of the 10. Many cells throughout the ventrointermediate subnucleus of the dorsal motor nucleus of the vagus nerve are seen ventrally to intermingle with the tyrosine hydroxylase neurons of the intermediate reticular zone. Computer reconstructions provided a three-dimensional view of the positions of substance P- and tyrosine hydroxylase-like immunoreactive neurons within the subdivisions of the dorsal motor nucleus of the vagus nerve. The uneven distribution of substance P- and tyrosine hydroxylase-like immunoreactive neurons within the subdivisions suggests an involvement of these substances in some, but not all, autonomic functions of the dorsal motor nucleus of the vagus nerve.

Adrenergic control of the secretion of anterior pituitary hormones

The hypothalamic hypophysiotrophic neurones are densely innervated by adrenergic and noradrenergic nerve terminals. Activation of alpha 1-adrenoceptors located in the brain stimulates the secretion of ACTH, prolactin and TSH. The effects of the alpha 1-adrenoceptors seem to be exerted on hypothalamic neurones that secrete vasopressin, CRH-41 and TRH. These mechanisms are important in the physiological control of the secretion of ACTH and TSH in humans. alpha 2-Adrenoceptors are not involved in the control of secretion of these hormones under basal conditions in humans. However, alpha 2-adrenoceptors exert an inhibitory effect that acts as a negative feedback mechanism, limiting excessive secretion of these hormones. There is no convincing evidence for the involvement of beta-adrenoceptors in the control of the secretion of these three hormones in humans. Studies on cultured anterior pituitary cells suggested that adrenaline and noradrenaline may influence the secretion of ACTH, prolactin and TSH directly at the level of the pituitary. However, these effects are not demonstrable in humans, and are likely to be due to alterations in the pituitary adrenoceptors during culture. In the case of growth hormone, activation of alpha 2-adrenoceptors located in the brain stimulates secretion of this hormone both by increasing the secretion of GHRH and by inhibiting the secretion of somatostatin. Activation of beta-adrenoceptors inhibits the secretion of growth hormone via an increase in the secretion of somatostatin. The effects of the central alpha 2- and beta-adrenoceptors are important in the physiological control of growth hormone secretion in humans. A considerable amount of evidence implicates brain alpha 1-adrenoceptors in the control of secretion of the gonadotrophins in experimental animals, but, despite intensive study, no convincing evidence has been found in humans of reproductive age.

Topography and collateralization of the dopaminergic projections to motor and lateral prefrontal cortex in owl monkeys

The sources and histochemical characteristics of dopaminergic projections to motor and premotor areas of cortex were investigated in owl monkeys in which information from related studies was used to subdivide cortex into motor fields. Brainstem projections to frontal cortex were identified by injections of different fluorescent dyes in the primary motor cortex (M1) and the supplementary motor area (SMA), first identified by microstimulation. Injections were also placed in dorsal premotor cortex and lateral prefrontal cortex. The distribution of retrogradely labeled neurons was related to the location of tyrosine hydroxylase immunolabeled neurons on the same or alternate brain sections to identify the dopamine (DA) neurons. All DA cortically projecting neurons were located in the A8-A10 complex, largely in its dorsal components, including the parabrachial pigmented n. of the ventral tegmental area (VTA), pars gamma of the substantia nigra compacta, and the dorsal part of the retrorubral area (A8). Fewer cells were in the midline groups of VTA (n. linearis rostralis and caudalis) and in the n. paranigralis. DA neurons projecting to M1, SMA, and prefrontal cortex were largely intermixed, and some of these neurons were double or triple labeled by the fluorescent dyes, indicating collateralization to two or three fields; DA cells projecting to M1 were more numerous than to the other locations. The dorsal components of the A8-A10 complex from which arose the DA mesocortical projection were also characterized by the presence of calbindin-immunoreactive neurons and by a dense neurotensin and noradrenergic terminal innervation. Compared to rodents or felines, the DA neurons projecting to the lateral frontal lobe of primates appear to be shifted dorsally and laterally in the nigral complex. The topographic overlap, partial collateralization, and common histochemical characteristics of the DA mesocortical neurons projecting to different fields of the lateral frontal lobe suggest that some degree of functional unity exists within this projection.

Activation of central alpha 1-adrenoceptors in humans stimulates secretion of prolactin and TSH, as well as ACTH

In normal male volunteers, intravenous infusions of the alpha 1-adrenergic agonist methoxamine stimulated the secretion of prolactin, thyroid-stimulating hormone (TSH), and adrenocorticotropic hormone (ACTH), and the effects were abolished by pretreatment with the alpha 1-antagonist prazosin. To investigate the site of action of methoxamine, its effects were compared with those of equipotent doses of norepinephrine, an alpha 1-agonist that reaches the pituitary gland and the median eminence after an intravenous infusion but, unlike methoxamine, does not cross the blood-brain barrier. Norepinephrine did not stimulate secretion of prolactin, TSH, or ACTH, suggesting that the stimulant alpha 1-adrenoceptors are located in the central nervous system and not directly on the pituitary gland or in the periphery. The alpha 2- and beta-adrenoceptor agonist properties of norepinephrine could not account for the differences from methoxamine, as pretreatment with prazosin did not modify hormone concentrations after norepinephrine. Methoxamine had no behavioral stimulant effects, as judged by visual analog scales that were sensitive to physiological changes in behavioral arousal. In four patients with hypothalamic dysfunction but responsive pituitary corticotrophs, methoxamine had no stimulant effect on the secretion of ACTH, confirming that the alpha 1-adrenoceptors that stimulate ACTH secretion are not located directly on the pituitary. None of the drugs had an effect on the secretion of growth hormone or the gonadotrophins.

Human fetal xenografts of brainstem tissue containing locus coeruleus neurons: functional and structural studies of intraocular grafts in athymic nude rats

Fetal human brainstem tissue including the nucleus locus coeruleus was transplanted to the anterior eye chamber of athymic nude rats. Most transplants survived and grew in the anterior chamber of the eye. After 9-15 months, the host animals were anesthetized and electrophysiological or in vivo electrochemical recordings were performed. The brainstem transplants contained spontaneously active neurons with regular single-spike firing patterns. The neurons responded to ipsilateral light stimulation with an increase in firing rate and to the alpha 2-receptor agonist clonidine with significantly decreased firing rates. In vivo electrochemical studies demonstrated reproducible noradrenergic overflow after local application of potassium. Immunohistochemical evaluation of the brainstem transplants showed an abundance of tyrosine hydroxylase-positive neurons and neurites in all transplants and a dense network of neurofilament-, synapsin-, and glial fibrillary acidic protein-positive profiles throughout the grafts. Taken together, the present physiological and histochemical data indicate that it is possible to obtain transplants containing a specific monoaminergic population within the brainstem from human fetal fragments and to maintain these transplants in oculo in athymic nude rats for at least 15 months, during which time noradrenergic neurons develop.

Dopaminergic neurons in the cat dorsal motor nucleus of the vagus, demonstrated by dopamine, AADC and TH immunohistochemistry

In the rostral part of the dorsal motor nucleus of the vagus of the cat, neurons do not contain histochemically detectable catecholamines, even though many perikarya contain both intense aromatic L-amino acid decarboxylase (AADC) immunoreactivity and strong monoamine oxidase enzymatic activity. Similarly located perikarya have distinct immunoreactivities to tyrosine hydroxylase (TH) and dopamine after treatment with colchicine. Since inhibition of monoamine oxidase fails to reveal dopamine in these cells, its absence in non-colchicine-treated animals cannot be due to rapid deamination. It appears that dopamine is synthesized by TH and AADC in dorsal motor vagal cells and is then rapidly transported from the perikarya.

Presumptive adrenergic neurons containing phenylethanolamine N-methyltransferase immunoreactivity in the medulla oblongata of neonatal swine

Given the importance of the swine (Sus scrofa) as an animal model for human development, physiology and disease, neurons containing the epinephrine-synthesizing enzyme, phenylethanolamine N-methyltransferase (PNMT), were mapped in the medulla oblongata of neonatal swine as a first step in identifying their roles in central autonomic control. Neurons were labeled immunocytochemically by using an antiserum to PNMT raised in rabbits against trypsin-treated enzyme purified from the bovine adrenal gland. The general regional organization of neurons expressing PNMT (-like) immunoreactivity (ir) in the neonatal swine was similar to data obtained in other species and, in some aspects, more closely resembled the pattern observed in the primate brain. Immunolabeled cells appeared to be more abundant and caudally more extensive than observed in other adult animals. PNMT-immunoreactive (ir) neuronal somata, however, were largely confined to the reticular formation in the ventrolateral quadrant and the nucleus tractus solitarii (NTS) and more restricted in distribution than those expressing tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (D beta H)-ir on serial transverse sections. A close correspondence was observed between the distributions of TH- and PNMT-ir neurons and processes throughout the C1 and C2 areas. However, in the C1 and C3 regions TH-ir neurons outnumbered those containing D beta H and PNMT-ir. In contrast, cell groups enriched in PNMT-ir neurons and processes were characterized by relatively weak D beta H-ir. In the ventrolateral medulla (VLM), PNMT-ir cell bodies were concentrated rostrally and extended from the caudal pole of the facial nucleus to a level posterior to the calamus scriptorius. The rostral VLM was characterized by an admixture of bipolar and multipolar primarily medium-diameter immunostained neurons. A prominent cell column (condensation) organized ventromedially to the nucleus ambiguus pars compactus (NAc). A loosely organized cluster bordered the lateral aspect of the special visceral efferent column; another smaller aggregate was located in the ventromedial reticular formation adjacent to the inferior olive. At middle medullary levels, PNMT-ir neurons formed two distinct subgroups (dorsal and ventral) interrupted by a band of precerebellar relay neurons that extended between the medial and lateral limbs of the lateral reticular nucleus of Walberg. At obex, the dorsal cell group formed a diagonal array and assumed a position dorsal and dorsolateral to the medial limb of LRN. This group was distinguished by bipolar neurons with axes of orientation directed perpendicularly to the majority of neurons in the rostal VLM or those lying near the caudal ventromedullary surface.(ABSTRACT TRUNCATED AT 400 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.

Melanin, tyrosine hydroxylase, calbindin and substance P in the human midbrain and substantia nigra in relation to nigrostriatal projections and differential neuronal susceptibility in Parkinson's disease

The anatomy of melanin-containing neurons and other midbrain structures was examined by tyrosine hydroxylase (TH), calbindin D28k, and substance P immunostaining. Greater than 95% of cells in the substantia nigra pars compacta contained melanin, but densely packed cells in a ventral tier had a low content of melanin and loosely packed cells in a dorsal tier had a high content of melanin. Approximately 60% in the gamma group and 40% in the retrorubral nucleus had a low content of melanin. TH immunostaining was moderate in both the ventral and dorsal tiers, but more intense in the gamma group and retrorubral nucleus. Calbindin D28k was absent from the ventral and dorsal tiers, but present in the gamma group and retrorubral nucleus. In the light of primate tracing studies these findings suggest that the ventral tier of the pars compacta projects to striosomes of the striatum and the dorsal tier, gamma group and retrorubral nucleus to the matrix compartment. The ventral tier is more vulnerable than the dorsal tier in Parkinson's disease, but the cells contain less melanin. Neither tier contains calbindin D28k. This differential vulnerability between the ventral and dorsal tiers cannot be explained by melanin or calbindin D28k.

Localization and characterization of angiotensin II receptor binding sites in the human basal ganglia, thalamus, midbrain pons, and cerebellum

Angiotensin II (Ang II) binding sites were localized in the thalamus, basal ganglia, midbrain, and pons of the human central nervous system by in vitro autoradiography, employing 125I-[Sar1, Ile8]angiotensin II as the radioligand. High-density binding occurs in the substantia nigra pars compacta, the interpeduncular nucleus and two of the raphe nuclei, the raphe magnus, and median raphe nucleus. Moderate densities occur in the caudate nucleus, putamen, bed nucleus of the stria terminalis, rostral linear nucleus, caudal linear nucleus, dorsal and paramedian raphe nuclei, locus coeruleus, and region of the subcoeruleus, oral dorsal paramedian nucleus, and A5/periolivary region. Low levels occur in the region between the subthalamic nucleus and the zona incerta, the mediodorsal thalamic nucleus, the central gray, the lateral and medial parabrachial nuclei, and the molecular layer of the cerebellum. The high density of Ang II receptor binding in the substantia nigra occurs over pigmented, presumably dopaminergic, neurons. The binding in this site, and in the striatum, is not observed in any of the other species we have studied. It displays similar pharmacological characteristics to the Ang II receptor binding site in other regions of the human brain. Overall we demonstrate a discrete pattern of Ang II receptor binding sites in the human brain, which shows a high correlation with the distribution observed in other mammalian species.

Catecholaminergic neurons in the parabrachial nucleus of normal individuals and patients with idiopathic Parkinson's disease

The parabrachial nucleus is believed to play a role in autonomic regulation. We have used the Fontana-Masson ammoniacal silver nitrate method and a tyrosine hydroxylase-immunostaining technique to demonstrate the presence of neuromelanin-containing catecholaminergic neurons in the parabrachial nucleus of normal individuals. In addition, we also show that there is a significant reduction of these catecholaminergic neurons and presence of Lewy bodies in the parabrachial nucleus of patients with idiopathic Parkinson's disease. These findings may be related to the several autonomic disturbances that may occur in idiopathic Parkinson's disease.

Multiple analysis of tyrosine hydroxylase and calmodulin distributions in the forebrain of the rat using a microphotometry system

Immunohistochemical distributions of tyrosine hydroxylase and calmodulin in the rat forebrain were analyzed quantitatively to confirm our previous results that the activities of central catecholamine-synthesizing enzymes are regulated by a calcium-calmodulin-dependent system. The adjacent slices of adult rat brain were stained immunohistochemically for tyrosine hydroxylase and for calmodulin, and the distributions and amounts of these proteins were measured by a fluorescence microphotometry system that was developed in our laboratory. Immunohistochemical fluorescence intensity was measured stepwise at 40 microns intervals through a 6 microns phi (on the slice) pin hole. Each stained brain slice was divided into approximately 100,000 areas, and measured for fluorescence intensity and displayed two- and three-dimensionally. Immunoreactive staining of tyrosine hydroxylase and calmodulin was observed in almost all areas of the brain, but its intensity varied. The relatively high levels of calmodulin could be observed in brain regions with high levels of tyrosine hydroxylase distribution, though high levels of tyrosine hydroxylase could not always be observed in brain regions where high levels of calmodulin were distributed. In the present study, high levels of tyrosine hydroxylase and calmodulin were distributed in the nucleus accumbens septi and the lateral part of the neostriatum regions in which the amount of dopamine was increased by the intraventricular administration of calcium. These findings suggest that the synthesis of central catecholamines is regulated by a calcium-calmodulin-dependent system.

Medullary catecholaminergic neurons in the normal human brain and in Parkinson's disease

Parkinson's disease is thought to cause degeneration of melanin-pigmented catecholaminergic neurons throughout the brainstem, but little quantitative information is available on the fate of catecholaminergic neurons associated with the dorsal vagal complex or medullary reticular formation. We therefore examined these neurons in the normal human medulla and in the brains of patients with Parkinson's disease, using both a melanin stain and immunohistochemical methods with an antiserum against tyrosine hydroxylase. The greatest numbers of catecholaminergic neurons in the ventrolateral reticular formation (A1/C1 group) were located in the far rostral medulla, whereas the largest populations of catecholaminergic cells in the dorsal vagal complex (A2/C2 group) were found at the level of the area postrema. No loss of cells was observed in the A1/C1 group in the parkinsonian brains. In contrast, the A2/C2 group showed moderate loss of neurons, most marked at the level of the area postrema. This difference was entirely due to the loss of neurons in the medial component of the A2 group, a population that normally is only lightly pigmented, while the heavily pigmented neurons in the ventral and intermediate components of the A2 complex were unaffected. Parkinson's disease causes degeneration only of selected populations of medullary catecholaminergic neurons, without apparent relationship to the extent of melanin pigmentation.

Organization of midbrain catecholamine-containing nuclei and their projections to the striatum in the North American opossum, Didelphis virginiana

Presumptive catecholamine (CA) neurons in the opossum midbrain were identified by tyrosine hydroxylase immunohistochemistry. In the midline, small to moderate number of CA cells were present in the rostral third of the nucleus raphe dorsalis and throughout the nucleus linearis. Ventrolaterally, such cells were observed in the deep tegmental reticular formation, in all subnuclei of the ventral tegmental area, and in the three subdivisions of the substantia nigra. The CA cells in these areas conform to the dopamine cell groups, A8, A9, and A10 as described in the rat. In several areas there appeared to be no separation between the CA neurons belonging to cytoarchitecturally different nuclei. In order to determine which CA neurons gave rise to striatal projections, the neostriatum was injected with True Blue (TB), and sections through the midbrain were processed for tyrosine hydroxylase (TH) and visualized by immunofluorescence. Neurons containing both TB and TH were observed in each of the CA cell groups mentioned above. The distribution of these cells confirmed organizational features that may be unique to the opossum's substantia nigra. In addition, different patterns of labeling resulted from caudate versus putamen injections, suggesting a rudimentary medial to lateral topography in the organization of nigrostriatal projections. Although our results suggest that the organization of midbrain CA neurons in the opossum is similar to that in placental mammals, it is clear that differences exist.

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.

Histamine neurons in human hypothalamus: anatomy in normal and Alzheimer diseased brains

The anatomy of histamine-immunoreactive cell bodies in normal adult human brain was examined in detail. In addition, the distribution of these cells in three cases of Alzheimer's disease was compared to the distribution of neurofibrillary tangles. Histamine-immunoreactive cell bodies were confined to the tuberal and posterior hypothalamus, forming the tuberomammillary nuclear complex. Most of the about 64,000 histamine neurons were large and multipolar. They comprised four distinct parts: (i) a major ventral part corresponding to the classical tuberomammillary nucleus, (ii) a medial part including the supramammillary nucleus and part of the posterior hypothalamic area, (iii) a caudal paramammillary part, and (iv) a minor lateral part. The parts showed some similarity with the subgroups in rat. In human, as compared to rat, the histamine neurons occupy a larger proportion of the hypothalamus. Numerous neurofibrillary tangles were found in the Alzheimer hypothalami, concentrated in the tuberomammillary area. Most of them were of globular type and extracellular, and only a minority were histamine immunoreactive. They may represent remnants of degenerated tuberomammillary neurons.

Distribution, morphology and number of monoamine-synthesizing and substance P-containing neurons in the human dorsal raphe nucleus

The distribution, morphology and number of serotonin-, catecholamine- and substance P-containing neurons in the human dorsal raphe nucleus were studied. Parallel series of sections were prepared from 10 human brainstems obtained at autopsy from patients without neurological disease aged between 42 and 88 years. The neurons were identified using immunohistochemistry with antibodies raised against phenylalanine hydroxylase (tryptophan hydroxylase-containing, serotonin neurons), tyrosine hydroxylase (catecholamine neurons) and substance P. A reference series of Nissl-stained sections was also prepared and data published separately were used to delineate the subnuclear divisions of the dorsal raphe nucleus and to establish the total number of neurons in each subnucleus. The following principal findings emerged. (1) Serotonin-synthesizing neurons are present in all regions of the dorsal raphe nucleus and their total number is 165,000 +/- 34,000. The same types of neurons as those seen in Nissl material characterize each of the five subnuclei (caudal, dorsal, ventral, ventrolateral and interfascicular). (2) Substance P-containing neurons mostly occupy the rostral part of the nucleus and their number is 74,600 +/- 17,600. (3) Catecholamine cells are only found in the rostral part of the dorsal raphe nucleus and their number is 5600 +/- 3400. (4) In the ventral and interfascicular subnuclei the combined number of serotonin-synthesizing and substance P-containing neurons exceeds the total number of Nissl-stained neurons suggesting that serotonin and substance P co-exist in a substantial part of the cell population of the dorsal raphe nucleus. This is further supported by the highly similar morphology and size of these neurons. It is concluded that there are demonstrable chemical differences between the various subregions of the human dorsal raphe nucleus. These differences are in harmony with the results of hodological studies in animals, which have demonstrated differential projection pathways emerging from this nucleus.

Aromatic L-amino acid decarboxylase-immunohistochemistry in the cat lower brainstem and midbrain

By indirect immunohistochemistry, the present study examined the distribution of neuronal structures in the cat medulla oblongata, pons, and midbrain, showing immunoreactivity to aromatic L-amino acid decarboxylase (AADC), which catalyzes the conversion of L-3, 4-dihydroxyphenylalanine (L-DOPA) to dopamine, and 5-hydroxytryptophan to serotonin (5HT). With simultaneous and serial double immunostaining techniques, immunoreactivity to this enzyme was demonstrated in most of the catecholaminergic and serotonergic neurons. We could also demonstrate AADC-IR cell bodies that do not contain tyrosine hydroxylase (TH-) or 5HT-immunoreactivity (called "D-type cells") outside such monoaminergic cell systems. At the medullo-spinal junction, very small D-type cells were found within and beneath the ependymal layer of the 10th area of Rexed surrounding the central canal. D-type cells were localized in the caudal reticular formation, nucleus of the solitary tract, a dorsal aspect of the lateral parabrachial nucleus, and pretectal areas as have been reported in the rat. Furthermore, the present study describes, in the cat brainstem, new additional D-type cell groups that have not been reported in the rat. Dense or loose clusters of D-type cells were localized in the external edge of the laminar trigeminal nucleus, dorsal motor nucleus of the vagus, external cuneate nucleus, nucleus praepositus hypoglossi, central, pontine, and periaqueductal gray, superficial layer of the superior colliculus, and area medial to the retroflexus. D-type cells were loosely clustered in the lateral part of the central tegmental field dorsal to the substantia nigra, extending dorsally in the medial division of the posterior complex of the thalamus and medial side of the brachium of the inferior colliculus. They extended farther rostrodorsally along the medial side of the nucleus limitans and joined with the pretectal cell group. Almost all these cells were very small and ovoid to round with 1-2 short processes with the exception of dorsal motor vagal cells. AADC-IR axons were clearly identified in the vagal efferent nerves, longitudinal medullary pathway, dorsal tegmental bundle rostral to the locus coeruleus. Serotonergic axons were identified not only in the central tegmentum field and lateral side of the central superior nucleus, but also in the ventral surface of the medulla oblongata. We describe principal densely stained fiber plexuses in the cat brainstem. The findings of the present study provide a morphological basis for neurons that decarboxylate endogenous and exogenous L-DOPA, 5HTP, and other aromatic L-amino acids.

Tyrosine hydroxylase-like (TH) immunoreactivity in human mesolimbic system

A practical methodology has been described for the use of human postmortem brain tissue in both tyrosine hydroxylase and dopamine beta-hydroxylase immunohistochemistry in which in situ perfusion with paraformaldehyde is followed by immersion fixation in Bouin's fixative. These studies indicate that TH-like immunoreactive fibers and terminals are not uniformly distributed in the human hippocampal complex. A distinctive lesser innervation is noted for the structures that compose the perforant pathway and may be important for the predilection of these areas for pathological change particularly as occurs in Alzheimer's disease.

Autoradiographic localization of dopamine D 1 and D 2 receptors in the brain of several mammalian species

Dopamine D 1 and D 2 receptor distributions were studied in the brain of the mouse, rat, guinea pig, cat and monkey by means of in vitro quantitative autoradiography using [3H]SCH 23390 and [3H]CV 205-502 to label D 1 and D 2 subtypes respectively. The distribution of both subtypes of receptors was similar within the basal ganglia of all species investigated. The highest densities for both subtypes were found in the nucleus caudatus, putamen, nucleus accumbens, olfactory tubercle and substantia nigra. Outside of the basal ganglia, differences in the distribution of both receptors were found among the species examined in regions such as cerebellum, cortex, hippocampus, superior colliculus and olfactory bulb. In all species D 1 receptor densities were higher than those of D 2. The absolute amount of both subtypes, however, varied among species. These results indicate that dopamine receptor distribution is well preserved in the basal ganglia during evolution, although differences among species exist in their distribution outside the basal ganglia and their absolute amount.

Neuropathology of immunohistochemically identified brainstem neurons in Parkinson's disease

Regional loss of immunohistochemically identified neurons in serial sections through the brainstem of 4 patients with idiopathic Parkinson's disease was compared with equivalent sections from 4 age-matched control subjects. In the Parkinson brains, the catecholamine cell groups of the midbrain, pons, and medulla showed variable neuropathological changes. All dopaminergic nuclei were variably affected, but were most severely affected in the caudal, central substantia nigra. The pontine noradrenergic locus ceruleus showed variable degrees of degeneration. There was also a substantial loss of substance P-containing neurons in the pedunculopontine tegmental nucleus. However, the most severely affected cell group in the pons was the serotonin-synthesizing neurons in the median raphe. In the medulla, substantial neuronal loss was found in several diverse cell groups including the adrenaline-synthesizing and neuropeptide Y-containing neurons in the rostral ventrolateral medulla, the serotonin-synthesizing neurons in the raphe obscurus nucleus, the substance P-containing neurons in the lateral reticular formation, as well as the substance P-containing neurons in the dorsal motor vagal nucleus. Lewy bodies were present in immunohistochemically identified neurons in many of these regions, indicating that they were affected directly by the disease process. These widespread but region- and transmitter-specific changes help account for the diversity of motor, cognitive, and autonomic manifestations of Parkinson's disease.