Postnatal development of striatal neurotensin immunoreactivity in relation to clusters of substance P immunoreactive neurons and the "dopamine islands" in the rat

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.

Brain neurotensin, psychostimulants, and stress--emphasis on neuroanatomical substrates

Neurotensin (NT) is a peptide that is widely distributed throughout the brain. NT is involved in locomotion, reward, stress and pain modulation, and in the pathophysiology of drug addiction and depression. In its first part this review brings together relevant literature about the neuroanatomy of NT and its receptors. The second part focuses on functional-anatomical interactions between NT, the mesotelencephalic dopamine system and structures targeted by dopaminergic projections. Finally, recent data about the actions of NT in processes underlying behavioral sensitization to psychostimulant drugs and the involvement of NT in the regulation of the hypothalamo-pituitary-adrenal gland axis are considered.

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.

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.

Age-related dopamine deficiency in the mesostriatal dopamine system of zitter mutant rats: regional fiber vulnerability in the striatum and the olfactory tubercle

Oxidant stress has been implicated in the pathogenesis of Parkinson's disease. To test the oxidant stress hypothesis of dopaminergic degeneration, age-related changes in the mesostriatal dopamine neuron system were compared between zitter mutant rats which have abnormal metabolism of oxygen species in the brain and Sprague-Dawley rat as a control using the neurochemistry and immunohistochemistry. Dopamine content in the caudate-putamen, nucleus accumbens and olfactory tubercle of zitter rats decreased significantly with age, and was lower than that found in corresponding age-matched controls. In the zitter rats, the reduction of dopamine was more prominent in the caudate-putamen than in the nucleus accumbens and olfactory tubercle. A characteristic decline of tyrosine hydroxylase-immunoreactive fibers in the caudate-putamen of the zitter rat was also observed. In the dorsolateral caudate-putamen, reduction of tyrosine hydroxylase-immunoreactive fibers was observed in the matrix-like area, whereas in the ventromedial caudate-putamen the reduction occurred in the patch-like areas. Degeneration of tyrosine hydroxylase-immunoreactive fibers which was characterized by swollen varicosities and clustered fibers was observed in the caudate-putamen and nucleus accumbens and preceded loss of normal tyrosine hydroxylase-immunoreactive fibers in the caudate-putamen. Thus, the depletion of dopamine in the terminal areas is related to axonal degeneration. However, there was no degenerative tyrosine hydroxylase-immunoreactive fibers in the olfactory tubercle at any examined age, but reductions of tyrosine hydroxylase-immunoreactive fibers and dopamine contents were noted in the olfactory tubercle after four months-of-age. Since the zitter rats have an abnormal oxygen metabolism, the degeneration of tyrosine hydroxylase-immunoreactive fibers could result from an accumulation of superoxide species. The present results provide support for the oxidant stress hypothesis of dopaminergic neuronal degeneration and further indicate the region-specific vulnerability of the nigrostriatal dopamine system.

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.

Patchy distribution of substance P receptor immunoreactivity in the' developing rat striatum

Developmental changes of the distribution pattern of substance P receptor (SPR) were investigated immunohistochemically in the rat striatum. The SPR immunoreactivity in the striatum first emerged at postnatal day 1 and transiently showed a patchy pattern of distribution until it displayed the adult pattern of homogeneous distribution by the third postnatal week. The SPR-immunoreactivity patches were most marked in the medial and dorsolateral parts of the striatum, as well as in the subcallosal streak. They matched tyrosine hydroxylase-enriched areas and, conversely, avoided calbindin-enriched zones. No neurons within the SPR-immunoreactive patches contained either choline acetyltransferase or somatostatin, which is known to be contained in intrinsic neurons in the striatum. The vast majority of SPR-immunoreactive patch neurons also contained DARPP-32, a phosphoprotein that is expressed in striatal projection neurons with D1 dopamine receptor. The results indicate that SPR-immunoreactive patches which appear transiently in the developing striatum are in register with the striatal patch compartment, and that SPR immunoreactivity within these patches may be expressed on projection neurons rather than intrinsic neurons. Such SPR immunoreactivity in projection neurons in striatal patches may fade out in adulthood.

Functional and molecular differentiation of the dopamine system induced by neonatal denervation

The administration of the neurotoxin 6-hydroxydopamine (6-OHDA) to damage the mesostriatal dopamine (DA) system in the neonate results in different neurochemical and behavioral consequences as compared to lesions made in adulthood. There have been few direct data to support the conclusion that the behavioral changes following neonatal 6-OHDA lesions reflect plasticity of the DA system. It is our hypothesis that the plasticity of the developing DA system is fundamentally different from that of the adult. Responses to 6-OHDA lesions can only be understood within the context of the status of the mesostriatal DA system at the time of the lesion. There are stages of development in the early postnatal period when certain components of the mesostriatal DA system are differentially sensitive to 6-OHDA lesions. These "windows" of vulnerability can be predicted from an analysis of the developmental expression of DA receptors and the maturation of the subpopulation of the mesostriatal DA system that innervates them. We review the differences in the behavioral plasticity of the adult and neonate sustaining 6-OHDA lesions to the mesostriatal DA system, the mechanisms responsible for the behavioral plasticity in the adult, and our conceptualization of which mechanisms are affected in the neonate.

The development of striatal patch/matrix organization after prenatal methylazoxymethanol: a combined immunocytochemical and bromo-deoxy-uridine birthdating study

The antimitotic drug methylazoxymethanol was used to destroy striatal patch neurons during their three-day-period of neurogenesis in the rat. Single or multiple injections of methylazoxymethanol were given during embryonic days 13-15, the period when patch neurons are known to undergo their final cell division. Methylazoxymethanol treatments produced a dramatic reduction in striatal volume. Immunocytochemical analysis revealed the continued presence of patches of neurons that were substance P-immunoreactive and devoid of calbindin and enkephalin immunoreactivity. Both the number of patches and relative volume occupied by patches was reduced in methylazoxymethanol-treated striata. Patch neurons could also be labelled by an intrastriatal injection of FluoroGold during the first postnatal week. The early ingrowth of nigrostriatal dopamine afferents was less noticeably patchy in the methylazoxymethanol-treated animals, in part owing to an overall increase in density. Large reductions in the number of neurons immunoreactive for choline acetyltransferase were observed, whereas NADPH diaphorase-stained neurons were not reduced unless methylazoxymethanol was given on embryonic day 15. Injections of bromo-deoxy-uridine, either during or after the 24 h that each methylazoxymethanol injection was considered to be effective, revealed that (i) some patch neurons continued to be generated in the 24-h period following methylazoxymethanol administration, and (ii) many patch neurons were generated after the effects of methylazoxymethanol had worn off. These findings demonstrate that it was impossible to completely eliminate the patches using methylazoxymethanol injections during the period of patch neurogenesis. However, methylazoxymethanol treatment during this time did produce a dramatic loss of cells and a relatively greater reduction in patch volume. Despite this disruption, the appropriate compartmentalization of neuroactive substances appeared to be maintained.

Mesencephalic grafts increase preprotachykinin-A mRNA expression in striatal grafts in an in oculo co-graft model

In oculo transplantation provides a powerful tool to study development and gene expression of isolated brain regions. In this study we grafted striatal and mesencephalic brain tissue to the anterior eye chamber and allowed it to survive for 2 and 6 weeks. Striatal or mesencephalic pieces were either grafted alone (single grafts) or together in close connection (co-grafts). As a control normal adult untreated rats were analyzed at the striatal and hippocampal level. Using non-radioactive in situ hybridization with digoxigenin-labeled riboprobes we detected preprotachykinin-A mRNA, a neuropeptide marker for striatal neurons. We report that adult normal rats show a strong expression of preprotachykinin-A mRNA in the striatum, medial habenula and piriform cortex, verifying the specificity of the method. Mesencephalic in oculo grafts did not reveal any staining for preprotachykinin-A mRNA. In single striatal grafts only a very weak expression of preprotachykinin-A mRNA was found at both time points investigated. Co-grafts grown for 2 weeks were not different from single striatal grafts, however, when striatum was grown together with ventral mesencephalon for 6 weeks the level of preprotachykinin-A mRNA was strong and near normal adult levels. We conclude that the mesencephalic dopaminergic innervation to the striatum might be a potent stimulus to neurons expressing preprotachykinin-A mRNA.

Localisation of parvalbumin-immunoreactive structures in primate caudate-putamen

To investigate the morphology, distribution, and connections of parvalbumin-containing neurones in the caudate-putamen of primates, perfuse-fixed sections were stained to reveal parvalbumin immunoreactivity. In agreement with previous observations, the caudate-putamen was rich in parvalbumin-positive neurones and neuropil. The neuropil staining was uneven such that the dense background staining was interspersed with zones of relatively weak staining. The distribution corresponded to the striosome/matrix system as defined by substance P or met-enkephalin immunostaining in adjacent sections. Because parvalbumin-positive neurones are present in regions known to project to the caudate-putamen and the majority of parvalbumin-positive terminals in the matrix formed asymmetric synapses, it is concluded that the uneven staining is probably due to afferents of the neostriatum. The morphology of the parvalbumin-immunoreactive neurones varied between the striosomes and matrix; those in the matrix were smaller and possessed dendritic arborisations that were relatively uniform, whereas those in the striosomes were generally more extensively stained and possessed a greater variation in their dendritic branching patterns. The dendrites frequently crossed the boundary between the striosomes and matrix. A population of giant parvalbumin-immunoreactive neurones was also observed in the putamen. Electron microscopic analysis revealed that, in addition to terminals forming asymmetric synapses, a smaller population formed symmetric synaptic specialisations and are presumed to be derived from the local parvalbumin-immunoreactive neurones. Terminals of the latter group formed synapses with medium-sized spiny neurones. Because parvalbumin-positive neurones receive input from the cortex, they may transmit cortical information to spiny neurones.

Cholinergic neurons are distributed preferentially in areas rich in substance P-like immunoreactivity in the caudate nucleus of the adult cat

The distribution of cells stained immunocytochemically for the cholinergic marker choline acetyltransferase was compared to the pattern of substance P immunoreactivity in the caudate nucleus of adult cats using a double-label immunocytochemical protocol and three-dimensional reconstructions of adjacent sections single-labeled for either substance P or choline acetyltransferase. Substance P immunoreactivity was distributed in a highly complex mosaic within the caudate nucleus of the cat. In the dorsal caudate nucleus, substance P-rich zones consisting of either clusters of substance P-positive cell bodies or fibers were seen against a lighter staining background. The density of cholinergic neurons was found to be significantly greater within these substance P-rich patches in comparison to surrounding regions. The pattern of substance P immunoreactivity within the ventral caudate nucleus differed from that in more dorsal regions. Clear substance P-rich patches were not seen in this region, but a large substance P-rich area consisting of a dense plexus of substance P-containing fibers was visible. Embedded within this substance P-rich area were fairly discrete patches of light substance P staining. As in the dorsal caudate nucleus, increased numbers of cholinergic neurons and processes were associated with substance P-rich regions in the ventral caudate nucleus. Choline acetyltransferase-positive perikarya also appeared to be concentrated in substance P-rich areas in the nucleus accumbens and olfactory tubercle. The results of this study suggest that a close relationship exists between the distribution of substance P fibers and cholinergic perikarya in the striatum of the cat.

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.

Temporal and compartmental restriction of neuron-specific enolase expression in the rat mesostriatal system

The striatum and the mesencephalic dopamine neurons which innervate it, are each organized into developmentally and biochemically distinct compartments. Striatal patches, characterized in the neonate by high concentrations of opiate receptors and substance P, are innervated prenatally by fibers originating in one group of midbrain dopamine neurons, the ventral tier. By the third postnatal day, a dense dopamine projection from neurons in the dorsal tier of the mesostriatal group innervates non-patch areas of the striatum, i.e. the matrix, and is followed by the appearance there of neurotensin, somatostatin and calcium binding protein. We have recently observed that the period of establishment of connections between dorsal tier dopamine neurons and their target cells in the striatal matrix is accompanied by a surge in expression of the gene coding for tyrosine hydroxylase (TH). In order to determine the overall metabolic state of mesencephalic and striatal neurons during the period of up-regulation of TH gene expression, we have applied immunocytochemistry for neuron specific enolase (NSE), and cytochrome oxidase histochemistry, known markers for neuronal activity, as well as TH immunohistochemistry to the mesencephalon and striatum of postnatally developing rats. At birth, both NSE and cytochrome oxidase were expressed almost exclusively in the patches, appearing in the matrix only after the 2nd postnatal day. Patches of NSE remained visible thru the 14th day. In the mesencephalon, cytochrome oxidase and immunoreactive NSE cells in adjacent sections, were present only in the pars reticulata (i.e. ventral tier). By day 8, both techniques identified nigral cells in the dorsal as well as ventral tiers.(ABSTRACT TRUNCATED AT 250 WORDS)

Compartmentalization of excitatory amino acid receptors in human striatum

Division of the mammalian neostriatum into two intermingled compartments called striosomes and matrix has been established by analysis of enzyme activity, neuropeptide distribution, nucleic acid hybridization, and neurotransmitter receptor binding. Striosomes and matrix are distinct with respect to afferent and efferent connections, and these regions provide the potential for modulation and integration of information flow within basal ganglia circuitry. The primary neurotransmitters of corticostriatal afferents are excitatory amino acids, but to date no correlation of excitatory amino acid receptors and striatal compartments has been described. We examined binding to the three pharmacologically distinct ionotropic excitatory amino acid receptors, N-methyl-D-aspartate, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid, and kainate, in human striatum using in vitro receptor autoradiography and compared the binding to striosomes and matrix histochemically defined by acetylcholinesterase activity. Our findings reveal increased binding to N-methyl-D-aspartate receptors and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors in matrix relative to striosomes and increased kainate receptor binding in striosomes relative to matrix. These results suggest that afferent input to the two striatal compartments may be mediated by pharmacologically distinct excitatory amino acid receptor subtypes.

Heterogeneous development of calbindin-D28K expression in the striatal matrix

In the present study, we attempted to trace the development of the striatal matrix by analyzing the ontogenetic expression of calbindin-D28K (calbindin), a calcium binding protein selectivity expressed in medium-sized neurons of the matrix compartment of the mature rat's caudoputamen. The localization of calbindin was documented in a series of developing rat brains, as was the compartmental location of these cells relative to tyrosine hydroxylase (TH)-immunostained dopamine islands, sites of future striosomes. Medium-sized striatal neurons appeared in the striatum at embryonic day (E) 20, and from their first appearance, the calbindin-positive neurons had highly heterogeneous distributions. They first formed a latticework of patches and bands in a ventral region of the caudoputamen. By postnatal day (P) 7, this early calbindin-positive lattice had evolved into a mosaic in which circumscript pockets of low calbindin-like immunoreactivity appeared in more extensive calbindin-rich surrounds. With further development, the mosaic gradually encroached on all but the dorsolateral caudoputamen, a district that is calbindin-poor at adulthood. A special lateral branch of the striatal calbindin system was also identified, distinct from the rest of the calbindin-positive mosaic in several developmental characteristics. In the parts of the caudoputamen where the developing calbindin system and dopamine island system were both present, the dopamine islands invariably lay in calbindin-poor zones. Most dopamine islands, however, only filled parts of the corresponding calbindin-poor zones. Moreover, there were some calbindin-poor zones for which TH-positive dopamine islands could not be detected. Thus during development, calbindin was expressed in the extrastriosomal matrix of the striatum, but the matrix could be divided into calbindin-rich and calbindin-poor zones. In the calbindin-rich regions, there were patches of especially intense calbindin expression and zones of weaker expression. These results suggest that there is neurochemical heterogeneity in the striatal matrix during the prolonged developmental period in which the early calbindin-positive lattice expands to form the calbindin-positive matrix of the mature striatum. Surprisingly, calbindin expression in the matrix, although eventually distributed in strictly complementary fashion to striosomes, does not originate as a system complementary to dopamine islands. The prolonged disparity between the borders of dopamine islands and calbindin-poor zones, and the different spatiotemporal schedules of development of the islands and the calbindin gaps suggest instead that the final match between the borders of striosomes and surrounding matrix results from dynamic processes occurring early in postnatal development. Candidate mechanisms for the gradual adjustment of these borders are proposed.

Neonatal 6-OHDA Lesions differentially affect striatal D1 and D2 receptors

Lesions to the dopamine (DA) system in early postnatal development have different behavioral consequences compared to lesions made in adulthood. Intrastriatal injections of the neurotoxin 6-hydroxydopamine (6-OHDA) on the day of birth (PO) or postnatal day 1 (P1) produce a selective supersensitivity to D1 receptor agonists and a subsensitivity to D1 antagonists (Neal and Joyce, 1991a). In this paper, we describe the long-term effects of early DA loss on DA receptor regulation. Pups received bilateral intrastriatal injections of the neurotoxin 6-OHDA (4 micrograms per striatum) on PO or P1. Adult rats were killed at 90 days of age and the brains were processed for quantitative autoradiography (QAR) or tyrosine hydroxylase (TH) immunocytochemistry. Cohorts were tested for the behavioral responses to the selective D1 receptor agonist SKF38393 (10 mg/kg). Neonatally lesioned rats exhibited increases in abnormal perioral movements in response to D1 receptor stimulation. There was a heterogenous and patchy loss (40-50%) of [3H]mazindol binding to high-affinity DA uptake sites (a marker of DA terminal density) and a similar loss of TH-like immunoreactivity within the striata of the neonatally lesioned rats. There was also a reduction in the number of mu-opioid receptor patches (labelled with [3H]naloxone), a marker for the striatal patch compartment, and a similar patchy loss of D1 binding sites (labeled with [3H]SCH23390). The binding of [3H]spiroperidol to D2 sites was not altered. This is in contrast to the changes observed following adult 6-OHDA lesions, wherein there is a significant increase in the number of D2 binding sites (Joyce, 1991a,b). The results are discussed with respect to the behavioral consequences of neonatal lesions and the differences between neonatal and adult lesions.

Postnatal ontogeny of cells expressing prepro-neurotensin/neuromedin N mRNA in the rat forebrain and midbrain: a hybridization histochemical study involving isotope-labeled and enzyme-labeled probes

The postnatal ontogeny of cells expressing prepro-neurotensin/neuromedin N messenger RNA (prepro-NT/NN mRNA) in the rat forebrain and midbrain was investigated by in situ hybridization histochemistry. According to the pattern of expression during development, the cells which express prepro-NT/NN mRNA can be roughly divided into 2 groups. In type I cells, prepro-NT/NN mRNA expression reaches a maximum in terms of content during the postnatal period. After this early peak, cells of this type express the same or less prepro-NT/NN mRNA, reaching a plateau at an adult level that still contains a high level of expression. In type II cells, prepro-NT/NN mRNA appears during the postnatal period, and the expression decreases dramatically after the first postnatal week, being almost undetectable by a few weeks after birth. Type I cells were observed in the following areas: the piriform cortex, field CA1 of Ammon's horn, subiculum, vertical, and horizontal limbs of the diagonal band of Broca, intermediate part of the lateral septal nucleus, bed nucleus of the stria terminalis, medial preoptic area, lateral hypothalamus, caudal part of the caudate putamen, medial, cortical, and central amygdaloid nuclei, ventral tegmental area, deep mesencephalic nucleus, cuneiform nucleus, dorsal raphe nucleus, laterodorsal tegmental nucleus, parabrachial nucleus, and oral part of the pontine reticular nucleus. Cells of type II were observed in the following areas: the mitral cell layer of the olfactory bulb, rostral part of the caudate putamen, (anterior) cingulate cortex, and retrosplenial cortex (posterior cingulate cortex).

Colchicine-induced expression of proneurotensin mRNA in rat striatum and hypothalamus

The effect of colchicine treatment on proneurotensin mRNA expression was examined using a sensitive non-radioactive in situ hybridization histochemistry technique with an enzyme-labelled antisense oligonucleotide probe. Intraventricular injection of colchicine rapidly induced strong neurotensin mRNA expression in a number of neurons in the dorsomedial part of the caudate putamen, and in the paraventricular, and arcuate nuclei while an induction of neurotensin mRNA was not observed in vehicle (saline)-injected animals. Neurotensin mRNA was not induced significantly in other periventricular areas such as the medial preoptic area or the lateral septum. These results indicate that colchicine can itself rapidly induce neurotensin mRNA expression and that this induction is specific to certain cell populations in the vicinity of the ventricles. These results demonstrate that colchicine should be used with caution in immunohistochemical studies demonstrating the normal distribution of peptide immunoreactivity or mRNA.

The striatal mosaic in primates: patterns of neuropeptide immunoreactivity differentiate the ventral striatum from the dorsal striatum

Patterns of immunoreactivity for calcium-binding protein, tyrosine hydroxylase and four neuropeptides in the ventral striatum (nucleus accumbens, olfactory tubercle and ventromedial parts of the caudate nucleus and putamen) were compared to patterns of these markers in the dorsal striatum (the majority of the neostriatum) in rhesus monkey. The striatal mosaic was delineated by calcium-binding protein and tyrosine hydroxylase immunoreactivities. Both markers were found preferentially in the matrix of the dorsal striatum. The mosaic configurations of tyrosine hydroxylase, but not calcium-binding protein immunoreactivity, were similar in dorsal and ventral striatal regions. Substance P and leucine-enkephalin were not distributed homogeneously; distinct types and the prevalence of patches of substance P and leucine-enkephalin immunoreactivity distinguish the dorsal striatum from the ventral striatum and distinguish the caudate nucleus from the putamen. In the dorsal striatum, substance P and leucine-enkephalin patches consist of dense islands of immunoreactive neurons and puncta or clusters of immunoreactive neurons marginated by a dense rim of terminal-like puncta; the matrix was also enriched in leucine-enkephalin-immunoreactive neurons but contained less substance P-immunoreactive neurons. Patches were more prominent in the caudate nucleus than in the putamen. In the caudate, compartments low in tyrosine hydroxylase and calcium-binding protein immunoreactivities corresponded to cytologically identified cell islands and to patches enriched in substance P and leucine-enkephalin. These patches had a discrete infrastructure based on the location of substance P and leucine-enkephalin-immunoreactive neurons and terminals. In the ventral striatum, patches that showed low levels of substance P and leucine-enkephalin immunoreactivities were embedded in a matrix rich in immunoreactive cell bodies, fibers and terminals. In the accumbens, regions showing little tyrosine hydroxylase were in spatial register with patches low in substance P and leucine-enkephalin. Neurotensin- and somatostatin-immunoreactive neurons or processes were also compartmentally organized, particularly in the ventral striatum. Neurotensin-immunoreactive neurons were present predominantly in the nucleus accumbens but not in the dorsal striatum. Some regions enriched in neurotensin immunoreactivity were spatially registered with zones low in tyrosine hydroxylase, substance P and zones enriched in leucine-enkephalin. Areas enriched in somatostatin-immunoreactive processes overlapped with both tyrosine hydroxylase-rich and -poor regions in the ventral striatum. Our results show that the chemoarchitectonic topography of the striatal mosaic is different in the dorsal and ventral striatum of rhesus monkey and that the compartmental organization of some neurotransmitters/neuropeptides in the ventral striatum is variable and not as easily divisible into conventional patch and matrix regions as in the dorsal striatum.(ABSTRACT TRUNCATED AT 400 WORDS)