Patterns of muscarinic cholinergic binding in the striatum and their relation to dopamine islands and striosomes

Direct dopamine terminal regulation by local striatal microcircuitry

Regulation of axonal dopamine release by local microcircuitry is at the hub of several biological processes that govern the timing and magnitude of signaling events in reward-related brain regions. An important characteristic of dopamine release from axon terminals in the striatum is that it is rapidly modulated by local regulatory mechanisms. These processes can occur via homosynaptic mechanisms-such as presynaptic dopamine autoreceptors and dopamine transporters - as well heterosynaptic mechanisms such as retrograde signaling from postsynaptic cholinergic and dynorphin systems, among others. Additionally, modulation of dopamine release via diffusible messengers, such as nitric oxide and hydrogen peroxide, allows for various metabolic factors to quickly and efficiently regulate dopamine release and subsequent signaling. Here we review how these mechanisms work in concert to influence the timing and magnitude of striatal dopamine signaling, independent of action potential activity at the level of dopaminergic cell bodies in the midbrain, thereby providing a parallel pathway by which dopamine can be modulated. Understanding the complexities of local regulation of dopamine signaling is required for building comprehensive frameworks of how activity throughout the dopamine system is integrated to drive signaling and control behavior.

Involvement of HCN Channel in Muscarinic Inhibitory Action on Tonic Firing of Dorsolateral Striatal Cholinergic Interneurons

The striatum is the most prominent nucleus in the basal ganglia and plays an important role in motor movement regulation. The cholinergic interneurons (ChIs) in striatum are involved in the motion regulation by releasing acetylcholine (ACh) and modulating the output of striatal projection neurons. Here, we report that muscarinic ACh receptor (M receptor) agonists, ACh and Oxotremorine (OXO-M), decreased the firing frequency of ChIs by blocking the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Scopolamine (SCO), a nonselective antagonist of M receptors, abolished the inhibition. OXO-M exerted its function by activating the Gi/o cAMP signaling cascade. The single-cell reverse transcription polymerase chain reaction (scRT-PCR) revealed that all the five subtypes of M receptors and four subtypes of HCN channels were expressed on ChIs. Among them, M2 receptors and HCN2 channels were the most dominant ones and expressed in every single studied cholinergic interneuron (ChI).Our results suggest that ACh regulates not only the output of striatal projection neurons, but also the firing activity of ChIs themselves by activating presynaptic M receptors in the dorsal striatum. The activation of M2 receptors and blockage of HCN2 channels may play an important role in ACh inhibition on the excitability of ChIs. This finding adds a new G-protein coupled receptor mediated regulation on ChIs and provides a cellular mechanism for control of cholinergic activity and ACh release in the dorsal striatum.

Cholinergic interneurons in the dorsal and ventral striatum: anatomical and functional considerations in normal and diseased conditions

Striatal cholinergic interneurons (ChIs) are central for the processing and reinforcement of reward-related behaviors that are negatively affected in states of altered dopamine transmission, such as in Parkinson's disease or drug addiction. Nevertheless, the development of therapeutic interventions directed at ChIs has been hampered by our limited knowledge of the diverse anatomical and functional characteristics of these neurons in the dorsal and ventral striatum, combined with the lack of pharmacological tools to modulate specific cholinergic receptor subtypes. This review highlights some of the key morphological, synaptic, and functional differences between ChIs of different striatal regions and across species. It also provides an overview of our current knowledge of the cellular localization and function of cholinergic receptor subtypes. The future use of high-resolution anatomical and functional tools to study the synaptic microcircuitry of brain networks, along with the development of specific cholinergic receptor drugs, should help further elucidate the role of striatal ChIs and permit efficient targeting of cholinergic systems in various brain disorders, including Parkinson's disease and addiction.

The non-human primate striatum undergoes marked prolonged remodeling during postnatal development

We examined the postnatal ontogeny of the striatum in rhesus monkeys (Macaca mulatta) to identify temporal and spatial patterns of histological and chemical maturation. Our goal was to determine whether this forebrain structure is developmentally static or dynamic in postnatal life. Brains from monkeys at 1 day, 1, 4, 6, 9, and 12 months of age (N = 12) and adult monkeys (N = 4) were analyzed. Nissl staining was used to assess striatal volume, cytoarchitecture, and apoptosis. Immunohistochemistry was used to localize and measure substance P (SP), leucine-enkephalin (LENK), tyrosine hydroxylase (TH), and calbindin D28 (CAL) immunoreactivities. Mature brain to body weight ratio was achieved at 4 months of age, and striatal volume increased from ∼1.2 to ∼1.4 cm(3) during the first postnatal year. Nissl staining identified, prominently in the caudate nucleus, developmentally persistent discrete cell islands with neuronal densities greater than the surrounding striatal parenchyma (matrix). Losses in neuronal density were observed in island and matrix regions during maturation, and differential developmental programmed cell death was observed in islands and matrix regions. Immunohistochemistry revealed striking changes occurring postnatally in striatal chemical neuroanatomy. At birth, the immature dopaminergic nigrostriatal innervation was characterized by islands enriched in TH-immunoreactive puncta (putative terminals) in the neuropil; TH-enriched islands aligned completely with areas enriched in SP immunoreactivity but low in LENK immunoreactivity. These areas enriched in SP immunoreactivity but low in LENK immunoreactivity were identified as striosome and matrix areas, respectively, because CAL immunoreactivity clearly delineated these territories. SP, LENK, and CAL immunoreactivities appeared as positive neuronal cell bodies, processes, and puncta. The matrix compartment at birth contained relatively low TH-immunoreactive processes and few SP-positive neurons but was densely populated with LENK-immunoreactive neurons. The nucleus accumbens part of the ventral striatum also showed prominent differences in SP, LENK, and CAL immunoreactivities in shell and core territories. During 12 months of postnatal maturation salient changes occurred in neurotransmitter marker localization: TH-positive afferents densely innervated the matrix to exceed levels of immunoreactivity in the striosomes; SP immunoreactivity levels increased in the matrix; and LENK-immunoreactivity levels decreased in the matrix and increased in the striosomes. At 12 months of age, striatal chemoarchitecture was similar qualitatively to adult patterns, but quantitatively different in LENK and SP in caudate, putamen, and nucleus accumbens. This study shows for the first time that the rhesus monkey striatum requires more than 12 months after birth to develop an adult-like pattern of chemical neuroanatomy and that principal neurons within striosomes and matrix have different developmental programs for neuropeptide expression. We conclude that postnatal maturation of the striatal mosaic in primates is not static but, rather, is a protracted and dynamic process that requires many synchronous and compartment-selective changes in afferent innervation and in the expression of genes that regulate neuronal phenotypes.

The disrupted basal ganglia and behavioural control: an integrative cross-domain perspective of spontaneous stereotypy

Spontaneous stereotypic behaviour (SB) is common in many captive animal species, as well as in humans with some severe psychiatric disorders, and is often cited as being related to general basal ganglia dysfunction. Despite this assertion, there is little in the literature examining SB specifically in terms of the basal ganglia mechanics. In this review, we attempt to fill this gap by offering an integrative, cross-domain perspective of SB by linking what we currently understand about the SB phenotype with the ever-growing literature on the anatomy and functionality of the basal ganglia. After outlining current models of SB from different theoretical perspectives, we offer a broad but detailed overview of normally functioning basal ganglia mechanics, and attempt to link this with current neurophysiological evidence related to spontaneous SB. Based on this we present an empirically derived theoretical framework, which proposes that SB is the result of a dysfunctional action selection system that may reflect dysregulation of excitatory (direct) and inhibitory (indirect and hyperdirect) pathways as well as alterations in mechanisms of behavioural switching. This approach also suggests behaviours that specifically become stereotypic may reflect inbuilt low selection threshold behavioural sequences associated with early development and the species-specific ethogram or, low threshold behavioural sequences that are the result of stress-induced dopamine exposure at the time of performance.

Basal Ganglia disorders associated with imbalances in the striatal striosome and matrix compartments

The striatum is composed principally of GABAergic, medium spiny striatal projection neurons (MSNs) that can be categorized based on their gene expression, electrophysiological profiles, and input–output circuits. Major subdivisions of MSN populations include (1) those in ventromedial and dorsolateral striatal regions, (2) those giving rise to the direct and indirect pathways, and (3) those that lie in the striosome and matrix compartments. The first two classificatory schemes have enabled advances in understanding of how basal ganglia circuits contribute to disease. However, despite the large number of molecules that are differentially expressed in the striosomes or the extra-striosomal matrix, and the evidence that these compartments have different input–output connections, our understanding of how this compartmentalization contributes to striatal function is still not clear. A broad view is that the matrix contains the direct and indirect pathway MSNs that form parts of sensorimotor and associative circuits, whereas striosomes contain MSNs that receive input from parts of limbic cortex and project directly or indirectly to the dopamine-containing neurons of the substantia nigra, pars compacta. Striosomes are widely distributed within the striatum and are thought to exert global, as well as local, influences on striatal processing by exchanging information with the surrounding matrix, including through interneurons that send processes into both compartments. It has been suggested that striosomes exert and maintain limbic control over behaviors driven by surrounding sensorimotor and associative parts of the striatal matrix. Consistent with this possibility, imbalances between striosome and matrix functions have been reported in relation to neurological disorders, including Huntington’s disease, L-DOPA-induced dyskinesias, dystonia, and drug addiction. Here, we consider how signaling imbalances between the striosomes and matrix might relate to symptomatology in these disorders.

Neurochemical characterization of the tree shrew dorsal striatum

The striatum is a major component of the basal ganglia and is associated with motor and cognitive functions. Striatal pathologies have been linked to several disorders, including Huntington’s, Tourette’s syndrome, obsessive–compulsive disorders, and schizophrenia. For the study of these striatal pathologies different animal models have been used, including rodents and non-human primates. Rodents lack on morphological complexity (for example, the lack of well defined caudate and putamen nuclei), which makes it difficult to translate data to the human paradigm. Primates, and especially higher primates, are the closest model to humans, but there are ever-increasing restrictions to the use of these animals for research. In our search for a non-primate animal model with a striatum that anatomically (and perhaps functionally) can resemble that of humans, we turned our attention to the tree shrew. Evolutionary genetic studies have provided strong data supporting that the tree shrews (Scadentia) are one of the closest groups to primates, although their brain anatomy has only been studied in detail for specific brain areas. Morphologically, the tree shrew striatum resembles the primate striatum with the presence of an internal capsule separating the caudate and putamen, but little is known about its neurochemical composition. Here we analyzed the expression of calcium-binding proteins, the presence and distribution of the striosome and matrix compartments (by the use of calbindin, tyrosine hydroxylase, and acetylcholinesterase immunohistochemistry), and the GABAergic system by immunohistochemistry against glutamic acid decarboxylase and Golgi impregnation. In summary, our results show that when compared to primates, the tree shrew dorsal striatum presents striking similarities in the distribution of most of the markers studied, while presenting some marked divergences when compared to the rodent striatum.

Temporal regulation of ephrin/Eph signalling is required for the spatial patterning of the mammalian striatum

Brain structures, whether mature or developing, display a wide diversity of pattern and shape, such as layers, nuclei or segments. The striatum in the mammalian forebrain displays a unique mosaic organization (subdivided into two morphologically and functionally defined neuronal compartments: the matrix and the striosomes) that underlies important functional features of the basal ganglia. Matrix and striosome neurons are generated sequentially during embryonic development, and segregate from each other to form a mosaic of distinct compartments. However, the molecular mechanisms that underlie this time-dependent process of neuronal segregation remain largely unknown. Using a novel organotypic assay, we identified ephrin/Eph family members as guidance cues that regulate matrix/striosome compartmentalization. We found that EphA4 and its ephrin ligands displayed specific temporal patterns of expression and function that play a significant role in the spatial segregation of matrix and striosome neurons. Analysis of the striatal patterning in ephrin A5/EphA4 mutant mice further revealed the requirement of EphA4 signalling for the proper sorting of matrix and striosome neuronal populations in vivo. These data constitute the first identification of genes involved in striatal compartmentalization, and reveal a novel mechanism by which the temporal control of guidance cues enables neuronal segregation, and thereby the generation of complex cellular patterns in the brain.

RGS4-dependent attenuation of M4 autoreceptor function in striatal cholinergic interneurons following dopamine depletion

Parkinson disease is a neurodegenerative disorder whose symptoms are caused by the loss of dopaminergic neurons innervating the striatum. As striatal dopamine levels fall, striatal acetylcholine release rises, exacerbating motor symptoms. This adaptation is commonly attributed to the loss of interneuronal regulation by inhibitory D(2) dopamine receptors. Our results point to a completely different, new mechanism. After striatal dopamine depletion, D(2) dopamine receptor modulation of calcium (Ca(2+)) channels controlling vesicular acetylcholine release in interneurons was unchanged, but M(4) muscarinic autoreceptor coupling to these same channels was markedly attenuated. This adaptation was attributable to the upregulation of RGS4-an autoreceptor-associated, GTPase-accelerating protein. This specific signaling adaptation extended to a broader loss of autoreceptor control of interneuron spiking. These observations suggest that RGS4-dependent attenuation of interneuronal autoreceptor signaling is a major factor in the elevation of striatal acetylcholine release in Parkinson disease.

Susceptibility of striatal neurons to excitotoxic injury correlates with basal levels of Bcl-2 and the induction of P53 and c-Myc immunoreactivity

The present studies evaluated the potential contribution of Bcl-2, p53, and c-Myc to the differential vulnerability of striatal neurons to the excitotoxin quinolinic acid (QA). In normal rat striatum, Bcl-2 immunoreactivity (Bcl-2-i) was most intense in large aspiny interneurons including choline acetyltransferase positive (CAT+) and parvalbumin positive (PARV+) neurons, but low in a majority of medium-sized neurons. In human brain, intense Bcl-2-i was seen in large striatal neurons but not in medium-sized spiny projection neurons. QA produced degeneration of numerous medium-sized neurons, but not those enriched in Bcl-2-i. Many Bcl-2-i-enriched interneurons including those with CAT+ and PARV+ survived QA injection, while medium-sized neurons labeled for calbindin D-28K (CAL D-28+) did not. In addition, proapoptotic proteins p53-i and c-Myc-i were robustly induced in medium-sized neurons, but not in most large neurons. The selective vulnerability of striatal medium spiny neurons to degeneration in a rodent model of Huntington's disease appears to correlate with their low levels of Bcl-2-i and high levels of induced p53-i and c-Myc-i.

The distribution of m4 muscarinic acetylcholine receptors in the islands of Calleja and striatum of rats and cynomolgus monkeys

The distribution of m4 muscarinic acetylcholine receptors, and their relation to a number other markers, was examined using immunocytochemical techniques. Staining in the dorsal striatum tended to be more pronounced in the striosomal than the matrix compartment of both rats and cynomolgus monkeys. Within the ventral striatum, immunoreactivity was more pronounced within the olfactory tubercle and the shell region of the nucleus accumbens than in the nucleus accumbens core and was especially marked within the lateral striatal stripe. Modest staining was also seen in the external plexiform layer of the olfactory bulb. By far, the most intense staining in the forebrain of both rats and cynomolgus monkeys was found in islands of Calleja, where it appeared to be a selective marker for the core or hilus regions of the islands, or an analogous region found adjacent to them. The core regions of different islands appear to be continuous with each other so as to form a complex three-dimensional structure, which is largely encased by layers of granule cells. The neuronal elements in the islands of Calleja, which express m4 receptors, remain to be identified, but it is unlikely that cholinergic neurons are a major locus of these receptors. Although there are certain similarities between the islands of Calleja and other components of the striatal complex, the current studies emphasize the extent to which the islands are unique in terms of their architecture and chemical anatomy.

CD15 immunoreactivity in the developing brain of a marsupial, the tammar wallaby ( Macropus eugenii)

We have studied the distribution of the CD15 epitope in the developing brain of an Australian diprotodontid metatherian mammal, the tammar wallaby ( Macropus eugenii), using immunohistochemistry in conjunction with hematoxylin and eosin staining. At the time of birth (28 days after conception), CD15 immunoreactivity labeled somata in the primordial plexiform layer of the parietal cortex in a similar position to that seen in the early fetal eutherian brain. CD15 immunoreactivity in the brain of the developing pouch-young wallaby was found to be localized on the surface of radial glia at boundaries between developmentally significant forebrain compartments in a similar distribution to that seen in developing eutherian brain. These were best seen in the developing diencephalon, delineating epithalamus, ventral and dorsal thalamus and hypothalamic anlage, and in the striatum. Immunoreactivity for CD15 identified radial glia marking the lateral migratory stream at the striatopallial boundary, peaking in intensity at P19 to P25. From P37 to P54, CD15 immunoreactivity also demarcated patch compartments in the developing striatum. In contrast, CD15 immunoreactivity in hindbrain structures showed some differences from the temporospatial pattern seen in eutherian brain. These may reflect the relatively early brainstem maturation required for the newborn wallaby to be able to traverse the distance from the maternal genital tract to the pouch. The wallaby provides a convenient model for testing hypotheses concerning the role of CD15 in forebrain development because all events in which CD15 may play a critical role in forebrain morphogenesis occur during pouch life, when the young wallaby is accessible to experimental manipulation.

Muscarinic m1 and m2 receptor proteins in local circuit and projection neurons of the primate striatum: anatomical evidence for cholinergic modulation of glutamatergic prefronto-striatal pathways

The cellular and subcellular localization of muscarinic receptor proteins m1 and m2 was examined in the neostriatum of macaque monkeys by using light and electron microscopic immunocytochemical techniques. Double-labeling immunocytochemistry revealed m1 receptors in calbindin-D28k--positive medium spiny projection neurons. Muscarinic m1 labeling was dramatically more intense in the striatal matrix compartment in juvenile monkeys but more intense in striosomes in the adult caudate, suggesting that m1 expression undergoes a developmental age-dependent change. Ultrastructurally, m1 receptors were predominantly localized in asymmetric synapse-forming spines, indicating that these spines receive extrastriatal excitatory afferents. The association of m1-positive spines with lesion-induced degenerating prefronto-striatal axon terminals demonstrated that these afferents originate in part from the prefrontal cortex. The synaptic localization of m1 in these spines indicates a role of m1 in the modulation of excitatory neurotransmission. To a lesser extent, m1 was present in symmetric synapses, where it may also modulate inhibitory neurotransmission originating from local striatal neurons or the substantia nigra. Conversely, m2/choline acetyltransferase (ChAT) double labeling revealed that m2-positive neurons corresponded to large aspiny cholinergic interneurons and ultrastructurally, that the majority of m2 labeled axons formed symmetric synapses. The remarkable segregation of the m1 and m2 receptor proteins to projection and local circuit neurons suggests a functional segregation of m1 and m2 mediated cholinergic actions in the striatum: m1 receptors modulate extrinsic glutamatergic and monoaminergic afferents and intrinsic GABAergic afferents onto projection neurons, whereas m2 receptors regulate acetylcholine release from axons of cholinergic interneurons.

The connections of the dopaminergic system with the striatum in rats and primates: an analysis with respect to the functional and compartmental organization of the striatum

This Commentary compares the connections of the dopaminergic system with the striatum in rats and primates with respect to two levels of striatal organization: a tripartite functional (motor, associative and limbic) subdivision and a compartmental (patch/striosome-matrix) subdivision. The topography of other basal ganglia projections to the dopaminergic system with respect to their tripartite functional subdivision is also reviewed. This examination indicates that, in rats and primates, the following observations can be made. (1) The limbic striatum reciprocates its dopaminergic input and in addition innervates most of the dopaminergic neurons projecting to the associative and motor striatum, whereas the motor and associative striatum reciprocate only part of their dopaminergic input. Therefore, the connections of the three striatal subregions with the dopaminergic system are asymmetrical, but the direction of asymmetry differs between the limbic versus the motor and associative striatum. (2) The limbic striatum provides the main striatal input to dopamine cell bodies and proximal dendrites, with some contribution from a subset of neurons in the associative and motor striatum (patch neurons in rats; an unspecified group of neurons in primates), while striatal input to the ventrally extending dopamine dendrites arises mainly from a subset of neurons in the associative and motor striatum (matrix neurons in rats; an unspecified group of neurons in primates). (3) Projections from functionally corresponding subdivisions of the striatum, pallidum and subthalamic nucleus to the dopaminergic system overlap, but the specific targets (dopamine cells, dopamine dendrites, GABA cells) of these projections differ. Major differences include the following. (1) In rats, neurons projecting to the motor and associative striatum reside in distinct regions, while in primates they are arranged in interdigitating clusters. (2) In rats, the terminal fields of projections arising from the motor and associative striatum are largely segregated, while in primates they are not. (3) In rats, patch- and matrix-projecting dopamine cells are organized in spatially, morphologically, histochemically and hodologically distinct ventral and dorsal tiers, while in primates there is no (bi)division of the dopaminergic system that results in two areas which have all the characteristics of the two tiers in rats. Based on the anatomical data and known dopamine cell physiology, we forward an hypothesis regarding the influence of the basal ganglia on dopamine cell activity which captures at least part of the complex interplay taking place within the substantia nigra between projections arising from the different basal ganglia nuclei. Finally, we incorporate the striatal connections with the dopaminergic system into an open-interconnected scheme of basal ganglia-thalamocortical circuitry.

Ephrin-A binding and EphA receptor expression delineate the matrix compartment of the striatum

The striatum integrates limbic and neocortical inputs to regulate sensorimotor and psychomotor behaviors. This function is dependent on the segregation of striatal projection neurons into anatomical and functional components, such as the striosome and matrix compartments. In the present study the association of ephrin-A cell surface ligands and EphA receptor tyrosine kinases (RTKs) with the organization of these compartments was determined in postnatal rats. Ephrin-A1 and ephrin-A4 selectively bind to EphA receptors on neurons restricted to the matrix compartment. Binding is absent from the striosomes, which were identified by mu-opioid receptor immunostaining. In contrast, ephrin-A2, ephrin-A3, and ephrin-A5 exhibit a different mosaic binding pattern that appears to define a subset of matrix neurons. In situ hybridization for EphA RTKs reveals that the two different ligand binding patterns strictly match the mRNA expression patterns of EphA4 and EphA7. Ligand-receptor binding assays indicate that ephrin-A1 and ephrin-A4 selectively bind EphA4 but not EphA7 in the lysates of striatal tissue. Conversely, ephrin-A2, ephrin-A3, and ephrin-A5 bind EphA7 but not EphA4. These observations implicate selective interactions between ephrin-A molecules and EphA RTKs as potential mechanisms for regulating the compartmental organization of the striatum.

Spatiotemporal expression gradients of the carbohydrate antigen (CD15) (Lewis X) during development of the human basal ganglia

The developmental expression pattern of the carbohydrate epitope CD15 (Lewis X, Le X) (alpha1-->3-fucosyl-N-acetyl-lactosamine) has been immunocytochemically evaluated in paraffin sections within the human basal ganglia from 10 weeks gestation to three years after birth. At 11 weeks of gestation, CD15 (Le X) positive radial glial cells were located in the anterior and dorsal parts of the lateral ganglionic eminence. Their processes ran from the subventricular zone radially in a highly ordered fashion to the dorsolateral margin of the caudate nucleus and further to the lateral rim of the putamen. At 12 weeks of gestation, strands of CD15 (Le X) material continued to the pial surface, forming a continuous CD15 (Le X) positive borderline separating the accumbens nucleus and olfactory tubercle from the piriform cortex. At 13 weeks of gestation the dorsal putamen was completely CD15 (Le X) immunoreactive along its perimeter and CD15 (Le X) patches, consisting of fine granular material, appeared at the dorsolateral margin of the putamen at this age; while the first CD15 (Le X) patches in the caudate nucleus were observed four weeks later. The matrix compartment of the caudate and dorsal putamen became gradually stained by granular CD15 (Le X) positive material into which CD15 (Le X) immunoreactive somata were embedded. The striking contrast in staining between patch and matrix compartments disappeared shortly after birth. The ventral striatum did not become immunoreactive until the last few weeks before birth. After the formation of CD15 (Le X) positive patches in the striatum (from 12 weeks of gestation), delicate CD15 (Le X) fibres, often accumulated in bundles and related to the striatal patches, became apparent coursing towards the external pallidal lamina and the globus pallidus. Immunoreactivity in the globus pallidus itself was transient, emerging from 16 weeks of gestation, reaching a peak at 21 weeks of gestation and disappearing by birth. Both processes, i.e. the occurrence of CD15 (Le X) striatopallidal fibres and the emerging immunoreactivity in their pallidal target, may be interrelated, so that ingrowing CD15 (Le X) positive axons from the striatum provoke CD15 (Le X) expression in the external and internal pallidum. The variable patterns and intensities of CD15 (Le X) expression are possibly related to periods of maturation of the striatum and the establishment of functional interactions within the basal ganglia. Differential staining of patch and matrix in the developing neostriatum suggests that a distinct phase of cellular adhesion or dishesion mediated by the CD15 (Le X) epitope occurs during establishment of the patch and matrix regions.

Differences in D2 dopamine receptor binding in the neostriatum between cats hemidecorticated neonatally or in adulthood

In order to study differences in response to neocortical injury sustained at different ages at the neurotransmitter level, we examined the density in D2 dopamine receptors in the neostriatum of cats hemidecorticated neonatally (N = 4) or in adulthood (N = 4), as well as in intact brains (N = 6). Receptor densities were measured using quantitative autoradiography and [3H]-spiperone binding in 12 regions of the neostriatum and nucleus accumbens septi. We found that the anterior lateral caudate nucleus on both sides of the brain contained a higher D2 receptor density in neonatal-lesioned as compared to adult-lesioned brains. Ipsilateral to the lesion, the increase was 101% (P < 0.05) and contralaterally it amounted to 77% (P < 0.05). Moreover, this region of the ipsilateral caudate nucleus of neonatal-lesioned cats tended to be more densely labeled than that of intact brain by 58% (P < 0.1). D2 receptor densities in adult-lesioned cats did not differ from that of intact controls. Comparison of these data with those of a former morphological study using the same animals suggested that this bilateral elevation of D2 receptor density in neonatally lesioned brains represents a higher mean density of binding sites per neuron. The elevation in the neonatal-lesioned cats might be a response of the striatum to neuroplastic changes in the striatal neuropil, including the corticostriatal afferents, since such changes are different in neonatal- as compared to adult-lesioned cats.

Cholinergic innervation in the human striatum: a three-compartment model

The mammalian striatum is divided into compartments that are anatomically and neurochemically distinct. The dorsal striatum has been described as containing two compartments, striosomes and matrix, while the ventral striatum is thought to have a more complex, multi-compartmental organization. In this study, we sought to characterize the compartmentalization of the dorsal and ventral portions of the human striatum using choline acetyltransferase as a marker. Image analysis was used to assess relative densities of immunostaining, and three distinct, choline acetyltransferase-immunostained compartments were demonstrated: intensely immunostained, moderately immunostained and weakly immunostained areas. The dorsomedial portion of the striatum was made up of moderately immunostained regions embedded within a densely immunostained background, thus manifesting the characteristic striosome/ matrix organization of the dorsal striatum. However, the ventral and lateral two-thirds of the striatum were made up of a mixture of densely immunostained, moderately immunostained and weakly immunostained areas, with the moderately immunostained region forming the bulk of the background tissue, and smaller, densely immunostained and weakly immunostained regions embedded within it. These compartments were compared to regions defined by distinct levels of acetylcholinesterase immunostaining in adjacent sections; the staining patterns produced by the two cholinergic markers were found to be identical except in some portions of the nucleus accumbens, where acetylcholinesterase immunostaining was found to be more intense than choline acetyltransferase immunostaining. The immunoreactive somata were mapped within sections stained for choline acetyltransferase taken from different rostrocaudal levels of the striatum, and the distributions and densities of immunoreactive somata within these three cholinergic compartments were determined. In general, the densities of cholinergic somata roughly correlated with immunostaining intensity of regions, e.g. the most intensely immunostained compartment also had the highest densities of cholinergic somata. However, in the rostroventral striatum, the densities of cholinergic somata in the weakly immunostained compartment roughly equalled the densities of cholinergic somata in the moderately immunostained compartment, suggesting that local axonal arborizations of cholinergic cells may differ in density or orientation between the two compartments, or, alternatively, that some of the cholinergic cells in the weakly immunostained compartment may project outside of the striatum. The large proportion of striatum displaying ventral striatal characteristics (a complex, multi-compart-mental organization) in humans relative to that observed in other mammals suggests that the role of the ventral striatum may be expanded and more highly differentiated in the human brain.

Synchronous patchy pattern of gene expression for adenylyl cyclase and phosphodiesterase but discrete expression for G-protein in developing rat striatum

The ontogeny of the gene expression for striatal adenylyl cyclase (AC), 63 kDa calmodulin-dependent phosphodiesterase (63 kDa CaM-PDE) and olfactory G-protein (Golf), all of which are expressed predominantly in the striatum, was studied by in situ hybridization histochemistry. In the peri- and early postnatal striatum, the gene expression for striatal AC and 63 kDa CaM-PDE showed a patchy pattern corresponding to the striatal patchy compartments enriched in several molecules involved in cAMP-signaling system including DARPP-32 (a dopamine and cyclic adenosine 3':5'-monophosphate-regulated phosphoprotein with an apparent M(r) of 32,000). On the other hand, Golf showed a homogeneous expression pattern throughout the striatal development. The present finding suggests that the gene expression for the three molecules directly involved in the cAMP-generating and degrading system is differentially regulated during the striatal development.

Mesostriatal dopamine markers in aged Long-Evans rats with sensorimotor impairment

Changes in the mesostriatal dopamine system associated with normal aging are observed in both human and laboratory animals, but the specific behavioral consequences of these nonpathological changes are largely unexplored. The present study (a) assessed the effects of normal aging on markers for the mesostriatal dopamine system, and (b) examined the relationship of age-related changes in this system to decline in reaction time performance. Decreased levels of midbrain dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) were observed in the aged rats as compared to young, but there was no evidence for age-related changes in the density of D1 or D2 receptor binding or the density of dopamine uptake sites. Some differences were observed when the aged rats were grouped according to reaction time performance. Aged RT-unimpaired rats exhibited higher density of D1 binding in rostrodorsal striatal patch areas, but lower overall levels of DA. In caudal striatum, aged RT-unimpaired rats exhibited lower DA and higher DOPAC levels.

Repeated scopolamine injections sensitize rats to pilocarpine-induced vacuous jaw movements and enhance striatal muscarinic receptor binding

This experiment was conducted to determine if repeated administration of the muscarinic antagonist scopolamine could increase pilocarpine-induced vacuous jaw movements and also enhance muscarinic receptor binding. Rats received daily injections of either scopolamine (0.5 mg/kg IP) or saline for 14 days. On day 15 rats received no injections of scopolamine, but did receive injections of pilocarpine (1.0, 2.0 or 4.0 mg/kg IP) or saline. After administration of pilocarpine or saline, all rats were observed for vacuous jaw movements and rearing behavior. The day after pilocarpine injections, rats were sacrificed and samples of tissue from the lateral neostriatum were removed to assess muscarinic receptor binding using 3H-QNB as the ligand. Analyses of the vacuous jaw movement data indicated that there was a significant dose-related increase in vacuous jaw movements induced by pilocarpine, and also that there was a significant enhancement of pilocarpine-induced vacuous jaw movements in rats pretreated with repeated scopolamine injections. There was not a significant scopolamine x pilocarpine interaction, suggesting that pretreatment with scopolamine produced an apparent parallel shift in the pilocarpine dose-response curve. Pilocarpine significantly suppressed rearing behavior, and scopolamine pretreatment significantly enhanced the suppression of rearing produced by pilocarpine. Analysis of the receptor binding data indicated that there was a significant increase in the number of muscarinic receptor sites (Bmax) in rats that received repeated scopolamine injections as compared to saline-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Islands and striosomes in the neostriatum of the rhesus monkey: non-equivalent compartments

Cytoarchitectonically defined cell-dense islands and regions of low acetylcholinesterase reactivity referred to as striosomes have been regarded as equivalent markers of the non-matrix compartment in the neostriatum. We examined islands and striosomes in adjacent sections to determine the degree of correspondence between the two neostriatal compartmental markers. Islands are aggregated centrally within the caudate, whereas striosomes are located throughout the entire nucleus, including the dorsolateral and ventromedial sectors. Moreover, even within the central sector, striosomes are more prevalent than islands. The present quantitative analysis suggests that islands may be further characterized as acetylcholinesterase-poor since the vast majority of islands co-localize with striosomes. However, due to the fact that striosomes are more numerous and more widely distributed throughout the neostriatum, less than a third of all striosomes are coincident with islands in adjacent sections. Comparison of each of these compartmental markers with the patterned terminal field of the prefrontal cortical projection revealed a near one-to-one correspondence between islands and terminal-free zones in the prefrontal projection. The percentage of striosomes which are aligned with fenestrations in the prefrontal projection is also quite high; however, because more striosomes than islands are found within the prefrontal terminal domain, some striosomes that fit within terminal-free zones do not have corresponding islands. These results indicate that islands and striosomes are not entirely equivalent compartmental markers and further suggest that contemporary, two-compartment models may not adequately represent the heterogeneity of the neostriatum.

Reduction in striatal D2 dopamine receptor mRNA and binding following AF64A lesions

Unilateral lesions by a cholinotoxin, receptor autoradiography, and in situ hybridization techniques were employed to determine if dopaminergic receptors are located on cholinergic interneurons in the caudate-putamen (CPu). Lesion of the CPu with small amounts of the cholinotoxin AF64A resulted in a significant decrease in D2 receptor mRNA and D2 receptor binding. The loss was more pronounced in lateral and central portions of the CPu. Results obtained using [3H] SCH23390 binding to D1 receptors indicated that there was no change in this dopamine receptor subtype in the AF64A-lesioned CPu. A decrease in D2 receptor mRNA and receptor binding in AF64A-lesioned animals indicates that a population of postsynaptic D2 receptors is associated with the cholinergic interneurons. Lack of any change in [3H]SCH23390 binding in the AF64A-lesioned animals suggests that D1 receptors are not located on cholinergic neurons. These results provide evidence to support the selectivity of the lesion when used as indicated.

Fos immunoreactivity after stimulation or inhibition of muscarinic receptors indicates anatomical specificity for cholinergic control of striatal efferent neurons and cortical neurons in the rat

Cholinergic neurons play a major role in the control of striatal activity via muscarinic receptors. The action of acetylcholine also appears to be dependent on the striosome-matrix compartmentalization of the striatum. This study was designed to find out whether modification of acetylcholine tone activates neurons in the striatum and forebrain of the rat. We looked for the appearance of immunoreactivity to Fos, a regulatory protein that is thought to convert synaptic signals into changes in gene expression. Pharmacological manipulation of muscarinic receptors was found to induce specific patterns of Fos immunoreactivity in distinct neuronal populations of the forebrain, including the striatum. Oxotremorine, a non-selective muscarinic agonist, induced Fos immunoreactivity in the striatum with a large predominance in striosomes (mostly in enkephalinergic neurons), in layers 4 and 6 of the cortex, and also in the piriform cortex and septum. The muscarinic agonist pilocarpine had an identical effect in the cortex, but the striosomal prevalence was less clear-cut than that observed after oxotremorine. Treatment with dopamine-depleting agents (6-hydroxydopamine or reserpine) and inhibitors of glutamate and opiate receptor (MK-801 and naloxone respectively) had no effect on the action of oxotremorine. This suggests that the induction of Fos provoked by oxotremorine does not involve dopamine, glutamate or opiates. Atropine, a non-specific muscarinic antagonist, also induced Fos immunoreactivity in the striatum but with matrix predominance (mostly in substance P neurons), as well as in the cingulate cortex, and the olfactory tubercle. Scopolamine, a muscarinic antagonist, induced Fos in both striosomal and matrix compartments in the striatum.(ABSTRACT TRUNCATED AT 250 WORDS)

Species-specific patterns of glycoprotein expression in the developing rodent caudoputamen: association of 5'-nucleotidase activity with dopamine islands and striosomes in rat, but with extrastriosomal matrix in mouse

The glycoprotein 5'-nucleotidase is a cell surface phosphatase and represents a new marker for striosomes in the adult rat caudoputamen. We report here on its developmental expression in the rat and mouse striatum, and show an unexpected converse 5'-nucleotidase chemoarchitecture of the caudoputamen in these closely related species. In the rat, 5'-nucleotidase activity was first visible as neuropil staining in tyrosine hydroxylase-positive dopamine islands of the midstriatum on postnatal day 1, and by the end of the first postnatal week, 5'-nucleotidase-positive dopamine islands also appeared rostrally. This compartmental pattern persisted thereafter, so that in adult animals, in all but the caudal caudoputamen, zones of enhanced 5'-nucleotidase staining were restricted to calbindin-D28k-poor striosomes. Weak 5'-nucleotidase activity also emerged in the matrix. In striking contrast, in the mouse striatum, enhanced 5'-nucleotidase activity was preferentially associated with extrastriosomal tissue. Enzymatic reaction first appeared on embryonic day 18, and developed over the first postnatal week into a mosaic pattern in which the matrix was stained but the dopamine islands were unstained. The matrix staining itself was heterogeneous. After the second postnatal week, most of the caudoputamen was stained, and in adult mice only rostral striosomes expressed low 5'-nucleotidase activity. We conclude that in rats, 5'-nucleotidase represents one of the few substances that maintains a preferential dopamine island/striosome distribution during striatal development. In mice, 5'-nucleotidase activity is expressed preferentially in the matrix during development, and its compartmental pattern is gradually lost with maturation, except very rostrally. These findings do not suggest an instructive role of the enzyme in striatal compartment formation in either species, but do suggest the possibility that 5'-nucleotidase contributes to the differentiation of striatal compartments during development.

5'-nucleotidase: a new marker for striosomal organization in the rat caudoputamen

The distribution of the adenosine-producing ectoenzyme 5'-nucleotidase was studied by means of a histochemical lead technique in the caudoputamen of normal adult rats and of rats in which injections either of 6-hydroxydopamine in the medial forebrain bundle or of ibotenic acid in the caudoputamen had been made 1-3 weeks previously. The patterns of striatal 5'-nucleotidase activity in these animals were compared in serial sections to the patterns of calbindin-D28k immunoreactivity and of 3H-naloxone ligand binding, which respectively mark the known matrix and striosome (patch) compartments of the caudoputamen. In the normal rats, 5'-nucleotidase activity was differentially concentrated in striosomes, where it produced a dense staining of the neuropil. The enzymatic staining followed a striosomal distribution in all but the caudal caudoputamen. Within the striatal matrix, 5'-nucleotidase staining also observed a lateromedial density gradient. Depletion of the dopamine-containing nigrostriatal innervation of the caudoputamen with 6-hydroxydopamine did not alter the striosomal selectivity of 5'-nucleotidase activity. Destruction of intrastriatal neurons by ibotenic acid led to a strongly 5'-nucleotidase-positive gliosis within the resulting necrotic region. Elsewhere in the caudoputamen, the enzyme's striosomal distribution was not detectably altered. We conclude that 5'-nucleotidase histochemistry provides an advantageous tool for detecting the striosomal architecture of the rat's caudoputamen. Moreover, 5'-nucleotidase is prominently associated with glial membranes in the central nervous system, so that the concentration of this enzyme in striosomes could mark these as sites of selective glial populations within striatum. These properties and actions of 5'-nucleotidase in purinergic neurotransmission and in neuroadhesion may contribute to the specialized functions of striosomes and matrix.

Development of high-affinity choline transport sites in rat forebrain: a quantitative autoradiography study with [3H]hemicholinium-3

The development of cholinergic terminals in rat brain has been quantitatively analyzed by [3H]hemicholinium-3 autoradiography. [3H]Hemicholinium-3 binds to high affinity choline transport sites, a specific marker for cholinergic neurons. In neonatal animals, kinetic and pharmacologic binding characteristics and regional distribution of [3H]hemicholinium-3 sites are consistent with specific cholinergic localization, as in the adult. The distribution of cholinergic terminals is described in the adult rat brain and during development, including heterogeneity of binding within several regions such as the striatum, nucleus accumbens, olfactory tubercle, cortex, and hippocampus. Early development and maturation vary greatly between brain regions. At embryonic day E18 and day 0, specific binding density is high only in the medial habenula. Development occurs primarily during the postnatal period in most brain regions examined. Many brain regions exhibit a lull in development between days 5 and 10, although the rate of development is highly region specific. Specific binding increases 2-12-fold between day 5 and adult animals, with adult density being achieved anywhere from day 15 to after day 21. The ontogeny of [3H]hemicholinium-3 binding sites generally occurs in a rostral to caudal direction. In the striatal body the characteristic lateral to medial gradient of binding site density is apparent by day 5, and development is more rapid in the lateral striatum. Patches of dense [3H]hemicholinium-3 binding coincident with acetylcholinesterase are observed on day 5 in the caudal striatum. The various patterns of cholinergic terminal development suggest that factors regulating cholinergic development are regional and complex.

Regional differences in the regulation of acetylcholine release upon D2 dopamine and N-methyl-D-aspartate receptor activation in rat nucleus accumbens and neostriatum

The effect of D2 dopamine receptor activation on either the electrically, or N-methyl-D-aspartate induced release of radiolabeled acetylcholine (ACh) was investigated in different areas of the nucleus accumbens and the neostriatum of rats, by using a superfusion technique. Sequential slices of 100 microns were chopped along either a rostrocaudal, mediolateral or dorsoventral axis. In every slice the effect of a supramaximal concentration of the selective D2 receptor agonist quinpirole on the release of ACh was measured. In the entire neostriatum the release of ACh was reduced by approximately 70% in the presence of quinpirole. By contrast, in the nucleus accumbens, a gradual decrease in the inhibitory effect of quinpirole on the release of ACh was observed along both the rostral-to-caudal and the lateral-to-medial axes. Whereas in the rostrolateral part a 50% inhibition could be observed, in the caudomedial part no significant inhibition could be detected. Also the N-methyl-D-aspartate induced release of ACh was smaller in the caudomedial part as compared to the rostrolateral part of the nucleus accumbens. It is concluded that the nucleus accumbens is a very heterogeneous structure with respect to the regulation of the release of ACh by D2 dopamine and N-methyl-D-aspartate receptor activation.

Quantitative image analysis with densitometry for immunohistochemistry and autoradiography of receptor binding sites--methodological considerations

Major technical progress in the development of computer-based image analysis has made possible the entry of autoradiography and immunohistochemistry into a new era where quantification by densitometry has become easily accessible. Autoradiography could become quantitative and displayed adequate reproducibility with the help of emulsion-coated films and the use of scales of standards of known radioactivity exposed and analyzed in parallel to the tissue sections. Immunohistochemistry after revelation by a color-based enzymatic technique can also become quantitative, providing that standardization of the crucial steps of the procedure and calibration through a parallel treatment of a scale of antigen standards can be ensured. Such an approach is described here in the rat with reference to tyrosine hydroxylase (TH), the main synthesizing enzyme for catecholamines, and with dopamine (DA) itself, a catecholaminergic neurotransmitter. The different parts of the procedure, which can influence the results, such as the fixation of the animals by perfusion and the evaluation of the fluctuations via the calibration curve, are discussed in detail. Biological validation of the proposed procedure is described by reference to experiments already well documented biochemically, such as the induction effect of reserpine on TH in the rat locus coeruleus and the depleting effect of alpha-methyltyrosine (AMPT), a well-known blocker of TH activity, on rat striatal DA content. Finally the importance of restricting the measurements to the (pseudo)linear portion of the calibration curve is illustrated by the autoradiographic identification of the differential intrastriatal repartition of the dopaminergic D1 and D2 receptor sites, particularly the dual patch-matrix compartments.

Morphological assessment of neuronal aggregates in the striatum of the rat

Regional variations in cell-packing density, culminating in the formation of cell clusters, is now a recognized morphological characteristic of the striatum that has been correlated, in some instances, with either regional histochemical variations or the distribution pattern of afferent fiber systems, or both. Within these cluster regions a further level of organization exists, in the form of discrete neuronal aggregates. The light microscopic morphology of these neurons and the nature of their intercellular contacts at the electron microscope level form the focus of this report. The neurons composing such aggregates are characterized by contiguous soma-somatic or soma-dendritic contact with extended regions of junctionlike symmetrical and consistent contacts where the distance between the cytoplasmic membranes of apposing neurons narrows to as close as 7 nm. Coated vesicles close to the contact areas are common. Three-dimensional computer reconstructions of serial 1 micron sections through aggregates in either the caudatoputamen or nucleus accumbens reveal "chains" of contiguous cells that frequently involve as many as 60 neurons. These contiguous cell aggregates are discrete entities within the larger clusters or islands. It is postulated that the cellular aggregates may represent the fundamental level of striatal organization and may be local modules for intrinsic information processing, modifying extrinsic data processed through the biochemical compartmentalization of the striatum imparted by striosomes, neuropeptides, and dopaminergic, thalamic and cortical afferents.

Comparative development of D1-dopamine and mu opiate receptors in normal and in 6-hydroxydopamine-lesioned neonatal rat striatum: dopaminergic fibers regulate mu but not D1 receptor distribution

The postnatal development of D1 dopaminergic receptors (D1 receptors) was investigated in the rat striatum in relation to distribution of mu opiate receptor patches and islandic tyrosine hydroxylase (TH)-immunoreactive fibers. The possible influence of dopaminergic (DA) fibers originating from the substantia nigra on the postnatal distribution of striatal D1 and mu receptors was also examined by producing an early 6-hydroxydopamine (6-OHDA) lesion of DA fibers. D1 and mu receptors were labeled with selective ligands: [3H]SCH 23390 and [3H]DAGO, respectively. During the first postnatal week, control rats showed patches of dense D1 binding sites in the entire rostro-caudal extension of the striatum. The localization of D1 receptor patches corresponded to striosomes identified by TH-immunoreactive islands. The striatal distribution of mu receptors was relatively homogeneous at postnatal day 0 (P0) but was clearly patchy at P3-P4. During the second postnatal week the striosomal pattern of D1 binding sites disappeared along a dorso-ventral gradient whereas mu binding sites remained distributed in patches. Densitometric measurements showed that there was a parallel increase of D1 binding sites in both striosomes and the surrounding matrix from P0 to P4. The disappearance of D1 receptor patches observed in the dorsal striatum at P9 was due to a faster increase of D1 binding sites in the matrix than in striosomes between P4 and P9 whereas a significant difference was still observed between these two compartments in the ventral striatum of P9 rats. During the third postnatal week, the density of D1 binding sites still increased but became progressively uniform in the whole striatum. The intrastriatal injection of 6-OHDA in 2-day-old rats produced a local disappearance of TH-immunoreactive fibers in the striatum and a distal degeneration of TH-immunoreactive cell bodies in the substantia nigra. However an early lesion of striatal DA fibers did not modify the pattern of development or the density of D1 binding sites during the postnatal period examined (1 and 3 weeks after the lesion). The distribution of mu receptors was unchanged 1 week after the lesion but showed a clear disorganization 3 weeks after the lesion. We discuss the differential influence of DA fibers on the distribution of D1 and mu receptors in the rat striatum and the possible role of DA in the regulation of the expression of mu receptors.

Muscarinic and dopaminergic receptor subtypes on striatal cholinergic interneurons

Unilateral stereotaxic injection of small amounts of the cholinotoxin, AF64A, caused minimal nonselective tissue damage and resulted in a significant loss of the presynaptic cholinergic markers [3H]hemicholinium-3 (45% reduction) and choline acetyltransferase (27% reduction). No significant change from control was observed in tyrosine hydroxylase or tryptophan hydroxylase activity; presynaptic neuronal markers for dopamine- and serotonin-containing neurons, respectively. The AF64A lesion resulted in a significant reduction of dopamine D2 receptors as evidenced by a decrease in [3H]sulpiride binding (42% reduction) and decrease of muscarinic non-M1 receptors as shown by a reduction in [3H]QNB binding in the presence of 100 nM pirenzepine (36% reduction). Saturation studies revealed that the change in [3H]sulpiride and [3H]QNB binding was due to a change in Bmax not Kd. Intrastriatal injection of AF64A failed to alter dopamine D1 or muscarinic M1 receptors labeled with [3H]SCH23390 and [3H]pirenzepine, respectively. In addition, no change in [3H]forskolin-labeled adenylate cyclase was observed. These results demonstrate that a subpopulation of muscarinic receptors (non-M1) are presynaptic on cholinergic interneurons (hence, autoreceptors), and a subpopulation of dopamine D2 receptors are postsynaptic on cholinergic interneurons. Furthermore, dopamine D1, muscarinic M1 and [3H]forskolin-labeled adenylate cyclase are not localized to striatal cholinergic interneurons.

Medial forebrain bundle of the rat: III. Cytoarchitecture of the rostral (telencephalic) part of the medial forebrain bundle bed nucleus

The boundaries of the medial forebrain bundle (MFB) of the rat have been presented in previous work on the structure of this fiber system (Nieuwenhuys et al.: J. Comp. Neurol. 206:49-81, '82). Neuronal cell bodies within these outlines constitute the bed nucleus of the MFB. Many fiber components of the MFB appeared to be spatially arranged within the bundle and featured an orderly topography (Veening et al.: J. Comp. Neurol. 206:82-108, '82). As the fibers of the MFB are thought to be a major source of afferents to the bed nucleus (Millhouse: In P.J. Morgane and J. Panksepp (eds): Anatomy of the Hypothalamus, Vol. 1. New York: Marcel Dekker, pp. 221-265, '79), the latter has been subjected in this and the companion study (Geeraedts et al.: J. Comp. Neurol. 294:537-568, '90) to a detailed cytoarchitectonic analysis. This analysis is based on continuous series sectioned in the three conventional planes. On the basis of cytoarchitectonic characteristics, including size and shape, staining intensity, packing density, and spatial orientation of the cell bodies, it was found that the bed nucleus of the MFB as described in the literature is by no means a cytoarchitectonic unit per se. Rather, the neuronal cell population located within the telencephalic stream of the MFB can be parcellated into a number of cellular groups, which partly or entirely belong to more-or-less known basal telencephalic structures. These structures are designated here as the MFB-related areas. They correspond largely to the subcommissural substantia innominata (SIC), the sublenticular substantia innominata (SIL), the nucleus of the diagonal band of Broca, the olfactory tubercle, the magnocellular preoptic nucleus (POMA), the lateral preoptic area (LPOA), and the interstitial nucleus of the stria medullaris (ISM). The complex of the MFB-related areas is surrounded by the following cellular entities: the nucleus accumbens (ACB), the caudatus-putamen region (CPU), the globus pallidus (GP), the bed nucleus of the stria terminalis (BST), the anterior amygdaloid area (AAA), the amygdaloid nuclear complex (A), the medial preoptic area (MPOA) and the anterior hypothalamic area (AHA). Both MFB-related areas and their surroundings have been identified and delimited in this study. This resulted in a new cytoarchitectonic atlas of the rat's basal telencephalon. Our atlas does not only show the relative positions of the above mentioned cellular groups, but also those of their subdivisions.(ABSTRACT TRUNCATED AT 400 WORDS)

Striosomal organization of cholinergic and dopaminergic uptake sites and cholinergic M1 receptors in the adult human striatum: a quantitative receptor autoradiographic study

The distribution of cholinergic pre- and postsynaptic markers and dopaminergic presynaptic markers was analyzed in the adult human striatum, using quantitative receptor autoradiography. The distribution of the different binding sites indicates that cholinergic and dopaminergic uptake sites display a striosomal organization, with a higher binding site density in the striatal matrix. M1 muscarinic cholinergic receptor distribution parallels the distribution of cholinergic presynaptic markers. Our data show that cholinergic and dopaminergic terminals, and M1 receptors are enriched in the matrix of the adult human striatum.

Autoradiographic localisation of D1 and D2 dopamine receptors in primordial striatal tissue grafts in rats

Using in vitro autoradiography the study examined the binding of the dopamine (DA) D1 receptor and D2 receptor radiolabelled ligands, [125I]SCH 23982 and [125I]sulpiride, respectively, to striatal sections of control rats, those with unilateral ibotenic acid (IA) lesions of the striatum and those with grafts of primordial striatal tissue implanted into the IA-lesioned striatum. In animals with IA-lesions, there was almost total degeneration of striatal neurones and a complete disappearance of both D1 and D2 receptors in the lesioned striatum. Within the striatal grafts, dense 'patches' of both D1 and D2 receptors were observed with densities comparable to those in the intact neostriatum. These data indicate that both D1 and D2 receptors are localized on the soma of intrinsic striatal neurones. Moreover, the specific localisation of D1 and D2 receptors in the grafts provides the neurochemical basis for the mechanisms by which the host nigrostriatal DA system can regulate the functional capacity of striatal grafts.

Angiotensin converting enzyme in the human basal forebrain and midbrain visualized by in vitro autoradiography

angiotensin converting enzyme converts angiotensin I to angiotensin II, a peptide that plays an important role in the central regulation of blood pressure and fluid and electrolyte homeostasis. However, the distribution of this enzyme in the human brain has not been well described. In this study, angiotensin converting enzyme was mapped in the human basal forebrain and midbrain by using quantitative in vitro autoradiography employing a derivative of a potent converting enzyme inhibitor, 125I-351A, as radioligand. This radioligand binds specifically and with high affinity to angiotensin converting enzyme and also exhibited these properties in binding to slide-mounted sections of human basal ganglia. In the basal ganglia, high levels of binding of 125I-351A are found in the caudate nucleus, putamen, nucleus accumbens, both divisions of the globus pallidus, and substantia nigra pars reticulata. High densities of labelling also occur in the ventral pallidum. In the hypothalamus, a moderate level occurs in the paraventricular and supraoptic nuclei, and a diffuse, low level of binding is found throughout the periventricular region. The organum vasculosum of the lamina terminalis, one of the circumventricular organs, displays the highest concentration of binding. The choroid plexus contains only moderate density of labelling in contrast to other mammalian species previously studied. Major fibre tracts are devoid of activity except for the posterior limb of the internal capsule, which contains fascicles of intense activity. In the midbrain, a moderate density of binding is detected in the periaqueductal gray. The dorsal, central linear, and, more caudally, the centralis superior medialis raphe nuclei also contain moderate densities of labelling. Angiotensin converting enzyme is heterogeneously distributed in the caudate nucleus and putamen, with distinct patches of high concentration surrounded by a matrix of diffuse, lower levels. In the caudate nucleus, these patches of high binding corresponded to striosomes since they register with acetylcholinesterase-poor zones. The high concentration of angiotensin converting enzyme found in the basal ganglia suggests that the enzyme may be involved in processing neuropeptides that occur in high concentrations in these structures. Possible substrates for converting enzyme include not only angiotensin I but also substance P and enkephalins, which are also concentrated in striosomes.

A neurochemical heterogeneity of the rat striatum as measured by in vivo electrochemistry and microdialysis

The neurochemical heterogeneity of the rat striatum was assessed in vivo by measuring subregional changes in extracellular dopamine and DOPAC by in vivo electrochemistry and microdialysis in response to amphetamine and the D2 antagonist, (-)-sulpiride. Both in vivo electrochemical and microdialysis experiments indicated a significant rostrocaudal gradient in dopamine release following amphetamine. The increase in dopamine release was highest in the rostral areas (over 800% of baseline values) and lowest in the most caudal subregion (425% of baseline). No lateromedial differences in dopamine release were observed. DOPAC levels decreased in dialysates but were similar for all 6 subregions examined. In contrast, D2 blockade with (-)-sulpiride revealed a lateromedial gradient in the increases seen for dopamine and DOPAC such that greater increases were observed in the lateral subregions. (-)-Sulpiride did not produce any differential effects along the rostrocaudal axis. The regional gradients detected in extracellular fluid changes of dopamine and DOPAC indicate that dopamine release is locally regulated by an interaction between the density of dopaminergic innervation to a particular subregion and the D2 receptor density.

Compartmental origins of the striatopallidal projection in the primate

The organization of striatopallidal projection neurons in the primate was studied by injecting horseradish peroxidase conjugated with wheat germ agglutinin and fluorescent markers (latex microspheres, Fluorogold, Diamidino Yellow or Nuclear Yellow) into the globus pallidus of 20 adult squirrel monkeys (Saimiri sciureus). Single injections of horseradish peroxidase conjugated with wheat germ agglutinin were placed so as to involve predominantly either one or both pallidal segments. In the double-tracer experiments, fluorescent tracer injections were centered in the external pallidum and deposits of horseradish peroxidase conjugated with wheat germ agglutinin were made in the internal pallidum. In control cases, injections were made in nearby parts of the internal capsule or striatum. Distributions of retrogradely labeled neurons in the striatum were analysed in relation to its striosomal architecture as demonstrated by histochemistry and immunohistochemistry. Three principal findings emerged. (1) Both the external and the internal segments of the primate pallidum receive input from both the caudate nucleus and the putamen, but different sets of striatal cells within these nuclei project to the two segments. (2) The striatopallidal projection in the primate originates mainly in the extrastriosomal matrix, although striosomes in the fields of labeling almost always contain some labeled neurons. (3) Heterogeneous groupings of striatopallidal projection neurons exist in the matrix and appear to be parts of three-dimensional projection-neuron arrays. We conclude that in the primate, separate lines of conduction lead from the striatum to the external and the internal pallidal segments, and raise the possibility that the cells of origin of these pathways form a mosaic in the extrastriosomal matrix.

A double-labeling method for AChE and fluorescent retrograde tracers

Staining for the degradative enzyme acetylcholinesterase (AChE) is an important tool in studying central cholinergic/cholinoceptive systems. AChE staining has also been useful in identifying the projections of AChE-containing neurons and codistribution of AChE with other neurotransmitters. The intensity and opacity of conventional AChE histochemical reaction products, however, pose problems for such double-labeling studies. Here, we have successfully combined a modified version (37) of the Koelle-Friedenwald AChE reaction with retrograde transport of the fluorescent tracer, Fluoro-Gold (FG). By omitting the final intensification steps of the Koelle-Friedenwald reaction, a translucent, light-stable reaction product is created. Viewed under darkfield illumination, this precipitate is of similar intensity and sensitivity to that produced by conventional AChE histochemical processing. Prior administration of an AChE-inhibitor yields preferential staining of AChE-positive neuronal somata. This nonintensified darkfield AChE (NIDA) histochemical method was compatible with visualization of retrogradely transported FG in AChE-positive neurons, allowing unambiguous identification of the projections of AChE-containing neurons.

Co-expression of neuropeptides in the cat's striatum: an immunohistochemical study of substance P, dynorphin B and enkephalin

The expression of tachykinin-like and opioid-like peptides was studied in medium-sized neurons of the caudate nucleus in tissue from adult cats pretreated with colchicine. Two methods, a serial thin-section peroxidase-antiperoxidase technique and a two-fluorochrome single-section technique, were applied. Quantitative estimates were made mainly with the peroxidase-antiperoxidase method. The numbers of neurons expressing substance P-like, dynorphin B-like, and enkephalin-like immunoreactivity were recorded in regions identified, respectively, as striosomes and extrastriosomal matrix. Striosomes were defined by the presence of clustered substance P-positive and dynorphin B-positive neurons and neuropil. Tests for the co-existence of enkephalin-like peptide and glutamate decarboxylase-like immunoreactivity were also made with the peroxidase-antiperoxidase method. Co-expression of substance P-like and dynorphin B-like immunoreactivities was the rule both in striosomes and in the matrix. In striosomes, substance P-like immunoreactivity was found in 96% of dynorphin B-immunoreactive neurons, and in the matrix 89% of dynorphin B-positive cells contained substance P-like immunoreactivity. Substance P/dynorphin B-positive neurons corresponded to over half (57%) of the neurons in striosomes but only 39% of the neurons in the matrix. Both in the matrix and in striosomes, about two-thirds of all neurons (63% and 65%, respectively) were identified as enkephalin-positive. Among all substance P/dynorphin B-positive medium-sized neurons, 76% also contained enkephalin-like antigen. The enkephalin-positive neurons characterized by triple peptide co-existence (enkephalin/substance P/dynorphin B) represented a mean of 63% of striosomal enkephalin-positive neurons (41% of all striosomal neurons) and 35% of matrical enkephalin-positive neurons (26% of all matrical neurons). Finally, nearly all enkephalin-positive neurons were immunoreactive for glutamate decarboxylase, and therefore probably GABAergic, but only about half the glutamate decarboxylase-positive population was enkephalin-immunoreactive. These findings suggest that neuropeptides from three distinct precursors may be co-localized in single medium-sized neurons in the striatum, and that the differential patterns of co-expression of substance P-like, dynorphin B-like, and enkephalin-like peptides may confer functional specializations upon subpopulations of GABAergic neurons giving rise to the efferent projections of the striatum. The linked expression of substance P-like and dynorphin B-like peptides in single neurons both in striosomes and matrix suggests that some regulatory mechanisms controlling peptide expression apply regardless of compartment.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholinesterase and Nissl staining in the same histological section

Acetylcholinesterase (AChE) enzyme histochemistry and Nissl staining are commonly utilized in neural architectonic studies. However, the opaque reaction deposit produced by the most commonly used AChE histochemical methods is not compatible with satisfactory Nissl staining. As a result, precise correlation of AChE and Nissl staining necessitates time-consuming comparisons of adjacent sections which may have differential shrinkage. Here, we have modified the Koelle-Friedenwald histochemical reaction for AChE by omitting the final intensification steps. The modified reaction yields a non-opaque reaction product that is selectively visualized by darkfield illumination. This non-intensified darkfield AChE (NIDA) reaction allows clear visualization of Nissl staining in the same histological section. This combined AChE-Nissl method greatly facilitates detailed correlation of enzyme and cytoarchitectonic organization.

Compartment-specific changes in the density of choline and dopamine uptake sites and muscarinic and dopaminergic receptors during the development of the baboon striatum: a quantitative receptor autoradiographic study

In the fetal and young primate neostriatum, cholinergic and dopaminergic markers show patches of high density surrounded by a lower-density matrix. In the adult, the same markers display the opposite pattern, a lower density in striosomes, surrounded by a higher-density matrix. In order to understand the developmental sequences leading to the adult compartmental organization of the primate neostriatum, a quantitative technique was used to study the ontogeny of pre- and postsynaptic components of cholinergic and dopaminergic neurons in baboon caudate nucleus and putamen. The development of specific uptake mechanisms for choline and dopamine and receptors was studied by means of quantitative autoradiography of the specific binding of [3H]-hemicholinium-3 [( 3H]-HC3) and [3H]-mazindol [( 3H]-MAZ) to the choline and dopamine uptake systems, respectively. [3H]-pirenzepine [( 3H]-PIR) was used to label M1 muscarinic receptors and [3H]-spiroperidol [( 3H]-SPI) was used to label striatal dopamine D2 receptors. Serial sections were used for each ligand to determine the precise anatomical relationships between the binding patterns of the different markers. Our aim was to determine whether the adult striosomal distribution of the binding sites studied was due to 1) a selective decrease in patch/striosomal binding density or 2) a selective increase in matrix binding density. Our studies show that a postnatal decrease in the density of [3H]-HC3 sites in the patch/striosomes and an increase in the matrix density of [3H]-MAZ sites are the primary, but not the sole, changes in the compartmental distribution of these sites leading to the adult striosomal organization of the striatal cholinergic and dopaminergic innervation. D2 receptors follow the general developmental pattern of [3H]-MAZ and [3H]-HC3, changing their density of distribution in both compartments during the developmental period examined. In addition, M1 muscarinic receptors already display their adult pattern in the newborn baboon striatum, and therefore represent one of the first neurochemical makers to adopt its mature organization.

Striatal muscarinic receptors are associated with substance P and somatostatin containing neurons

The cellular localization of muscarinic acetylcholine binding sites (mAChr) in relation to immunohistochemically characterized cell populations within the rat caudate nucleus has been determined using in vitro autoradiography of the reversible antagonist ligand, quinuclidinyl benzilate [( 3H]QNB). The pattern of autoradiographic silver grain deposition in the striatum was contrasted with the localization of two peptide-containing neuronal populations in the striatum. Substance P-immunoreactive somata demonstrated prevalent association of mAChr binding sites, as did somatostatin-immunoreactive cells. Substantially more striatal muscarinic binding sites were aggregated over the somatostatin interneuron population of the caudate nucleus than were associated with the substance P somata in concurrently performed experiments. This data further substantiates the heterogeneity in organization of the caudate nucleus, and the results are discussed in relation to the processing of information within this basal ganglia region.

In vivo neurochemical and anatomical heterogeneity of the dopamine uptake system in the rat caudate putamen

The neurochemical and anatomical heterogeneity of dopamine uptake blockade was studied at a medial and lateral position in each of 3 rostrocaudal areas of the rat caudate-putamen. In vivo voltammetric measures of extracellular dopamine indicated a lateral-to-medial and rostral-to-caudal gradient in the effect of uptake blockade. The percentage increase in dopamine was greatest in the rostrolateral area (300%) and least in the caudomedial area (10%). The existence of these lateromedial and rostrocaudal gradients was confirmed by tissue content measures of DOPAC and dopamine to DOPAC ratios in each area. The rostrocaudal gradient in the effect of uptake blockade was independent of the rostrocaudal gradient in dopamine tissue content. The regional gradients detected in dopamine uptake blockade may indicate a heterogeneous distribution in the number of uptake sites, a regional variation in the affinity of the uptake site for the blocker and/or altered neuronal activity mediated by an action of the blocker on dopaminergic cell bodies.

Three-dimensional organization of the striosomal compartment and patchy distribution of striatonigral projections in the matrix of the cat caudate nucleus

Acetylcholinesterase staining on successive frontal or sagittal sections was used to determine the three-dimensional organization of the striosomal and matrix compartments in the adult cat caudate nucleus. Reconstruction drawings of the acetylcholinesterase-poor zones (striosomes) indicated that the striosomal compartment is a labyrinthine network organized in the rostrocaudal and mediolateral axis which is reproducible from one animal to another. Four main anteroposterior channels converging in the mediorostral pole of the caudate nucleus were distinguished. Seven to eight diagonally oriented channels crossing the previous ones were seen also in the mediolateral axis on the central core of the caudate nucleus. The pattern of organization of the numerous and tortuous striosomal channels was more complicated medially, while the lateral part of the caudate nucleus was represented mainly by the matrix compartment. In addition, a sub-compartmentation of the matrix was demonstrated by retrograde tracing studies made by injecting either horseradish peroxidase-wheat germ agglutinin, [14C]amino acids or a mixture of horseradish peroxidase-wheat germ agglutinin and [14C]amino acids in several areas of the substantia nigra pars reticulata. Labelled patches were seen with both tracers, their topographical localization depended on the nigral injection site but reconstruction analysis indicated that the populations of cells which innervate the substantia nigra pars reticulata originate in the two third lateral parts of the caudate nucleus all along its rostrocaudal extension. Examination of horseradish peroxidase-wheat germ agglutinin labelled cells indicated that not all cells were labelled in patches suggesting a further sub-compartmentation of these patches. Finally, a comparison of the topographical distributions of labelled patches and of striosomes revealed that most patches were located in the extrastriosomal matrix.