Transient increase of brain derived neurotrophic factor mRNA expression in substantia nigra reticulata after partial lesion of the nigrostriatal dopaminergic pathway

By using non-isostopic in situ hybridization we have demonstrated a transient increase of BDNF mRNA in the lateral subregion of the substantia nigra pars reticulata 1 week after intrastriatal application of 6-OH-DA. These changes correlate with a partial reduction of dopamine (DA) content in the striatum but with a normal tyrosine hydroxylase immunoreactivity in substantia nigra pars compacta. Our data suggest that non-DA, BDNF expressing cells in substantia nigra pars reticulata may play a role in neuronal protection after partial lesions of the DA nigrostriatal pathway.     

c-fos and tyrosine hydroxylase expression after an excitotoxic lesion on the nigrostriatal system: a study on the effects of hypoxia used as a preconditioning stimulus

Hypoxia-ischemia during the perinatal period causes excitotoxic lesions in sensitive brain areas, such as the striatum. The impact of hypoxia-ischemia on nigral neurons is less well known. Hypoxia alone, a less traumatic event without overt histological sequelae, has neuroprotective properties when used as a preconditioning stimulus. In some pathologies, injured neurons of the nigrostriatal system in the adult may be the result of neurodegenerative processes that originated at early stages of life. The effects of hypoxia on the immunoreactivity to tyrosine hydroxylase of the dopaminergic neurons of the substantia nigra pars compacta and the effects of a period of hypoxia previous to an excitotoxic lesion were examined by means of histological and Western blot methods, at immediate and late periods of the episode. By counting the number of tyrosine hydroxylase-stained neurons and c-fos-positive nuclei a short period after injection of quinolinic acid into the striatum, we observed that hypoxia induced a more marked decrease in the number of tyrosine hydroxylase-stained neurons. On the contrary, c-fos-positive profiles decreased in the substantia nigra pars reticulata of the quinolinic acid-injected animals after the preconditioning hypoxia. Hypoxia alone did not affect the number of tyrosine hydroxylase-positive neurons in the pars compacta nor did hypoxia induce c-fos expression in the pars reticulata. More sensitive Western blot analysis of tissue blocks that included the whole substantia nigra demonstrated the same trend as the immunohistochemical results. We conclude that the responses of the substantia nigra neurons to hypoxia are regionalized and potential neuroprotective effects may depend on the vulnerability of each neuronal type.     

Heterogeneous distribution of cytochrome oxidase activity in the rat substantia nigra: correlation with tyrosine hydroxylase and dynorphin immunoreactivities

Cytochrome oxidase (COase) activity, an endogenous marker of neuronal activity, was examined in the substantia nigra of the adult rat at the light-microscopic level. In addition, the pattern of histochemical staining observed for COase activity was correlated with immunohistochemistry for tyrosine hydroxylase (a marker of dopaminergic neurons) and for dynorphin (a peptide present in afferents from the striatum). Differential oxidative metabolic activity was revealed in subregions of the substantia nigra by COase histochemistry. Neurons of the substantia nigra pars compacta (SNc), ventral tegmental area, and ventrally displaced dopaminergic neurons were characterized by little or no staining for COase. In contrast, the substantia nigra pars reticulata (SNr) possessed a heterogeneous distribution of COase activity that was characterized by denser staining in the ventrolateral than the dorsomedial part of the nucleus throughout its rostrocaudal extent, with the exception of the most rostral levels. This pattern of COase activity was inversely correlated with the density of ventrally descending tyrosine hydroxylase-positive dendrites arising from the medial portion of the SNc, as well as with the density of dynorphin immunoreactivity. The results suggest that the SNc and SNr possess distinct levels of oxidative metabolic activity. Furthermore, within the SNr itself, different levels of COase activity characterize subpopulations of neurons which may be differentially regulated by both striatal and dopaminergic influences.     

Complementary Distribution of Calbindin D-28k and Parvalbumin in the Basal Forebrain and Midbrain of the Squirrel Monkey

The distribution of cell bodies expressing either calbindin D-28k or parvalbumin immunoreactivity in the basal forebrain and midbrain of squirrel monkeys (Saimiri sciureus) was studied on contiguous sections incubated with monoclonal antibodies raised against calbindin or parvalbumin. In the nucleus accumbens, medium-sized calbindin-positive neurons formed two cell bridges joining the ventral part of the striatum to the olfactory tubercle, whereas medium-sized parvalbumin-positive cells in the same area were much less numerous and more uniformly distributed. The medial and dorsal septal nuclei contained a small number of elongated calbindin-positive neurons and only a few parvalbumin-immunoreactive cells. In the nucleus of the diagonal band of Broca, calbindin and parvalbumin were found to label two distinct but closely intermingled neuronal populations. In the striatum, medium-sized calbindin-immunoreactive cells occurred in very large numbers and appeared to be confined to the extrastriosomal matrix. Medium-sized, parvalbumin-immunoreactive neurons were also present in the striatum but they were less numerous than the calbindin-positive cells. The calbindin-positive neurons in the dorsal portion of the striatum were less intensely stained than those in the ventral portion, whereas this pattern did not occur for neurons expressing parvalbumin immunoreactivity. At the pallidal level, neurons in both segments were devoid of calbindin but displayed a very strong parvalbumin immunoreactivity. Most of the large neurons of the nucleus basalis of Meynert were strongly calbindin-immunoreactive and many of them invaded dorsally the medullary laminae of the pallidal complex. The neurons of the subthalamic nucleus were markedly enriched with parvalbumin but displayed only light calbindin staining. In the substantia nigra/ventral tegmental area complex, calbindin-immunoreactive cells abounded in the ventral tegmental area and in the dorsal tier of the pars compacta of the substantia nigra, but were absent in the ventral tier of the pars compacta and in the entire pars reticulata of the substantia nigra. In contrast, numerous parvalbumin-immunoreactive neurons occurred in the pars reticulata and pars lateralis, but none were found in the pars compacta and ventral tegmental area. These findings reveal that the patterns of calbindin and parvalbumin distribution in primate basal forebrain and midbrain are strikingly complementary, suggesting a synergistic role for these calcium-binding proteins in basal forebrain and midbrain function.     

Morphological characteristics of the acetylcholinesterase-containing neurons in the CNS of DFP-treated monkeys.

The distribution of acetylcholinesterase (AChE, EC3.1.1.7) within extrapyramidal and related structures was studied in 4 monkeys following the i.m. administration of bis-(1-methylethyl) phosphorofluoridate (di-isopropylfluorophosphate: DFP). In 1 animal, sacrificed 4 hr after the injection of 0.43 mg/kg C, AChE is virtually absent in all structures. In the other 3 animals, which received 0.20 mg/kg DFP 10, 12 and 18 hr prior to sacrifice, AChE activity is greatly reduced in the neuropil of those structures which normally show intense AChE activity in pharmacologically unmanipulated monkeys. As a consequence of the lower background AChE activity in the latter 3 DFP-treated monkeys, the perikarya and processes of several groups of neurons can be readily identified. The perikarya and processes of two types of neurons of the neostriatum, representing a small percentage of all neurons in this structure, are intensely stained. They apparently correspond to the chromatic giant aspiny neurons and the achromatic medium-size "spidery aspiny" neurons. Most perikarya and processes of the neurons of the medial and lateral divisions of the pallidum, as well as the morphologically similar neurons of the pars reticulata of the substantia nigra, display light to moderate AChE activity. The pars compacta of the substantia nigra contains a small number of intensely stained elongated and triangular neurons and numerous moderately stained ovoid neurons whose processes are very lightly reactive. The cell bodies of the neurons of the subthalamic nucleus and associated groups of neurons (nucleus ansae peduncularis) are moderately stained whereas the perikarya and processes of the subnucleus compactus of the pedunculopontine tegmental nucleus are intensely and moderately stained, respectively. Numerous large and multipolar neurons associated with the lenticular nucleus (intralamellar groups) or the pallidum (peripallidal groups) including the nucleus ansae lenticularis have somata and processes which show an intense AChE activity. Certain of the latter groups of neurons, partially interspersed with the neurons of the substantia innominata, correspond in part to the nucleus basalis of Meynert. The present data are compatible with the idea that the large AChE neurons of the neostriatum may be the source of the acetylcholinesterasic striatopallidal and strionigral fibers. The similarity between the neurons of the pallidum and those of the pars reticulata of the substantia nigra suggests that the latter structure may represent a caudal extension of pallidal tissue. Therefore, the nigrothalamic projection, which has been claimed to originate in the pars reticulata of the substantia nigra, would correspond to pallidothalamic projections.     

Immunohistochemical localization of voltage-gated calcium channels in substantia nigra dopamine neurons

The rhythmic firing of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNc) is thought to be mediated by nifedipine-sensitive Ca(2+) channels, although an involvement of omega-conotoxin-sensitive Ca(2+) channels is also suggested. In an attempt to localize such Ca(2+) channels at both the regional and cellular levels, their expression and distribution patterns were immunohistochemically investigated in the rat SNc. The three distinct subtypes of voltage-gated Ca(2+) channels were tested: the class B N-type alpha 1 subunit (CNB1), the class C L-type alpha 1 subunit (CNC1) and the class D L-type alpha 1 subunit (CND1). A large number of SNc neurons showed intense immunoreactivity against CND1 and they were distributed throughout the entire extent. By contrast, many fewer neurons displayed less intense CNC1 immunoreactivity and many of them were located in the lateral aspect of the SNc. No immunoreactivity against CNB1 was detected in the SNc. Moreover, double immunofluorescence analysis in combination with tyrosine hydroxylase staining revealed that virtually all DA neurons were CND1-immunoreactive whereas many DA neurons especially in the medial SNc exhibited only faint or no immunoreactivity against CNC1. Both CNC1 and CND1 were expressed in cell bodies and proximal dendrites of SNc DA neurons, whilst their distal dendrites that penetrated into the substantia nigra pars reticulata expressed CND1 alone. Thus, the ubiquitously and intensely expressed class D alpha 1 subunit of L-type Ca(2+) channels that is sensitive to both nifedipine and omega-conotoxin may be responsible for the pacemaker activity of SNc DA neurons.     

Substance P synaptic interactions with GABAergic and dopaminergic neurons in rat substantia nigra: An ultrastructural doublelabeling immunocytochemical study

The distribution of substance P (SP), tyrosine hydroxylase (TH), and glutamic acid decarboxylase (GAD) immunoreactivity in the substantia nigra of the rat was studied by means of an ultrastructural double-labeling immunocytochemical method. Direct synaptic contact between SP-immunoreactive terminals and GAD-positive nigral neurons was more often observed in the pars lateralis than the pars reticularis and was rarely observed in the pars compacta. Substance P-positive terminals also formed synapses with cell bodies and dendrites of TH-positive, dopaminergic neurons in the pars compacta and pars reticulata. Multiple SP-immunoreactive terminals were often observed with symmetrical and, less frequently, asymmetrical synapses on individual TH-containing dendrites. Evidence of SP-containing terminals contacting both GABAergic and dopaminergic neurons in the substantia nigra suggests a direct excitatory action upon nigral projection neurons.     

Ventral mesencephalic neurons containing both cholecystokinin- and tyrosine hydroxylase-like immunoreactivities project to forebrain regions

The coexistence of cholecystokinin- and tyrosine hydroxylase-like immunoreactivities within neurons of the rat ventral mesencephalon was analyzed by using an indirect immunofluorescence technique for the simultaneous demonstration of two antigens in the same tissue section. A high degree of colocalization was observed in the substantia nigra pars compacta, in which 80-90% of all labeled neurons at rostral and up to 70% at intermediate levels contained both cholecystokinin and tyrosine hydroxylase. At caudal levels, the incidence of colocalization declined to approximately 30-50%. All of the immunoreactive perikarya in the substantia nigra pars lateralis were labeled with both substances. Other areas of the ventral midbrain that exhibited a moderate proportion of neurons immunoreactive for both cholecystokinin and tyrosine hydroxylase included the ventral tegmental area, interfascicular nucleus, and rostral and caudal linear nuclei. In addition, coexistence was occasionally observed within neurons of the central and ventral periaqueductal gray matter, supramammillary region, peripeduncular region, retrorubral field, and extremely rarely, within the substantia nigra pars reticulata. Cell bodies containing tyrosine hydroxylase-like immunoreactivity (indicative of dopamine) usually outnumbered those containing the peptide except in the supramammillary region and in the ventral periaqueductal gray matter, where the cholecystokinin perikarya were present in higher numbers. The double-labeling colocalization technique was combined with fluorescence retrograde tracing to determine some of the forebrain projections of these neurons. Ventral midbrain neurons containing both cholecystokinin and tyrosine hydroxylase were found to project to the caudate-putamen, nucleus-accumbens, prefrontal cortex, and amygdala. These projections originated from neurons located predominantly in the substantia nigra pars compacta and the ventral tegmental area. Thus, cholecystokinin occurs within the well-known dopaminergic nigrostriatal pathway in the rat. Overall, these results demonstrate that a significant proportion of the dopamine neurons giving rise to the ascending mesotelencephalic projections also contain the peptide cholecystokinin.     

Comparative distribution of mRNAs for glutamic acid decarboxylase, tyrosine hydroxylase, and tachykinins in the basal ganglia: an in situ hybridization study in the rodent brain

Neurotransmitter-related messenger RNAs were detected by in situ hybridization in sections of rat and mouse brains by using 35S-radiolabelled RNA probes transcribed from cDNAs cloned in SP6 promoter-containing vectors. The distribution of messenger RNAs for glutamic acid decarboxylase, tachykinins (substance P and K), and tyrosine hydroxylase was examined in the striatum, pallidum, and substantia nigra. Dense clusters of silver grains were observed with the RNA probe complementary of the cellular messenger RNA for glutamic acid decarboxylase (antisense RNA) over most large neurons in the substantia nigra pars reticulata and medium-sized to large neurons in all pallidal subdivisions. A few very densely and numerous lightly labelled medium-sized neurons were present in the striatum. Among the areas examined, only the striatum contained neurons labelled with the antisense tachykinin RNA. Most of these neurons were of medium size, and a few were large. With the antisense tyrosine hydroxylase RNA, silver grains were found over neurons of the substantia nigra pars compacta and adjacent A10 and A8 dopaminergic cell groups. No signal was observed with RNAs identical to the cellular messenger RNA for glutamic acid decarboxylase or tachykinin (sense RNA). These results show a good correlation with immunohistochemical studies, suggesting that documented differences in the distribution and the level of glutamic acid decarboxylase, tyrosine hydroxylase, and substance P immunoreactivities in neurons of the basal ganglia are related to differences in the level of expression of the corresponding genes rather than to translation accessibility, stability, or transport of the gene products.     

The neostriatal mosaic. I. Compartmental organization of projections from the striatum to the substantia nigra in the rat

Combined neuroanatomical techniques were used to examine the organization of the striatal projection to the substantia nigra in the rat. Both double anterograde axonal tracing methods (Phaseolus vulgaris leuco-agglutinin (PHA-L) and 3H-amino acid tract tracing) and double fluorescent retrograde axonal transport tracing methods were used to examine the relationship among striatal neurons projecting to separate areas of the substantia nigra. Additionally, the distributions of retrogradely labeled striatonigral projection neurons were charted relative to the neurochemically distinct striatal "patch" compartment, identified by substance P- or leu-enkephalin-like immunoreactivity, and the complementary "matrix" compartment, identified by somatostatin-like immunoreactive fibers. These studies show two distinct types of organization in the striatonigral projections. One type is topographic in that the mediolateral relationships among these striatal efferent neurons are roughly maintained by their termination patterns in the substantia nigra, while the dorsoventral relationships are inverted. Projections from any part of the striatum, however, are distributed throughout the rostrocaudal axis of the substantia nigra. Despite their general topographic organization, the variable and dispersed nature of such projections from individual striatal loci results in partial overlap of afferent fields from separate striatal areas. The second type of organization is nontopographic and provides a different system for convergence of inputs from separated striatal areas that is superimposed on the rough topographic system. In this other projection system the mediolateral and dorsoventral relationships typical of the topographically ordered system are not maintained and are sometimes reversed. For example, PHA-L injected into the dorsal striatum labels a topographic (inverted relationship) projection to the ventral substantia nigra pars reticulata but also a smaller and separate projection to the dorsal pars reticulata and adjacent pars compacta. Retrograde tracer deposits in the pars compacta label neurons in the ventral striatum (the inverted relationship) but also clusters of neurons in the dorsal striatum. These clusters are in the neurochemically defined patch compartment whereas neurons in the matrix are labeled by injections into the pars reticulata. The dendrites of both retrogradely filled patch and matrix neurons are confined to the compartment containing their cell bodies, suggesting a restriction that would functionally segregate extrinsic striatal afferents shown in other studies to be confined to either patches or matrix.(ABSTRACT TRUNCATED AT 400 WORDS)     

Identification of the substantia nigra pars lateralis in the macaque using cytochrome oxidase and fiber stains

Classically, the substantia nigra is divided into three subdivisions, the pars compacta, the pars reticulata, and the pars lateralis. The purpose of the present study was to develop methods for routine identification of the non-compacta subdivisions in the macaque monkey. First, the pars reticulata and pars lateralis were identified based on their Nissl features. Second, nearby cytochrome oxidase and Gallyas fiber stained sections were examined for these two subdivisions. In both stains, a dorsolateral region could be identified to contain large fiber bundles. This region is coextensive with the pars lateralis as identified in Nissl-stained preparations. Lastly, we examined the complete extent of the pars lateralis using the cytochrome oxidase procedure. We conclude that in the macaque monkey the pars lateralis can be identified as a distinct nigral subdivision by using cytochrome oxidase and fiber staining techniques.     

Postnatal development of acetylcholinesterase in the caudate-putamen nucleus and substantia nigra of rats.

The postnatal development of acetylcholinesterase (AChE, EC 3.1.1.7) and NADH-diaphorase was examined in the caudate-putamen nucleus and substantia nigra of rats ranging from 3 to 90 days in age. From 3 to 15 days post partum islands of AChE and NADH-diaphorase activity were observed in the caudate-putamen nucleus. Individual neuronal somata could also be seen in AChE-stained sections up to 15 days. At later ages neuropil staining became increasingly dense, and this presumably accounted for the infrequent visualization of cell bodies in the brains of older animals. During development AChE appeared in the caudate-putamen nucleus in a lateral to medial topographic order; analogously, enzyme staining in the neostriatum reappeared in the same lateral to medial topographic order in adult rats following irreversible AChE inhibition by intramuscularly injected bis-(1-methylethyl)phosphorofluoridate (di-isopropylfluorophosphate: DFP). Furthermore, DFP treatment in mature animals revealed the presence of AChE in striatal neurons having morphologies similar to those observed in newborn rats. A similar time-course of postnatal AChE development was observed in the substantia nigra. In both the pars compacta and pars reticulata individual cell bodies, which were visible at early ages (3-10 days), became increasingly obscured at later times after birth by extra-somata staining. Between the 6th and 15th postnatal days AChE-containing fibers were seen projecting apparently from pars compacta into pars reticulata. Comparison of the present results with histochemical data of other investigators on the postnatal development of monoamines indicated the likelihood of cholinergicmonoaminergic interactions in the neostriatum and substantia nigra.     

Interrelationship of the distribution of neuropeptides and tyrosine hydroxylase immunoreactivity in the human substantia Nigra

The relationship in the human substantia nigra of peptidergic fibers with intrinsic dopaminergic neurons was studied in adjacent coronal sections of the mesencephalon immunohistochemically stained for enkephalin (ENK), substance P (SP), and tyrosine (TH) hydroxylase immunoreactivity. TH-positive elements are present in the substantia nigra in at least two different arrangements: 1) a dorsal tier of rather loosely arranged neurons, which is continuous medially with the ventral tegmental area and laterally with the retrorubral area, 2) a ventral tier of more closely packed neurons, clusters of which frequently form finger-like extensions deep into the pars reticulata. This ventral region contains TH-positive dendrites extending ventrally into the pars reticulata. The distribution of ENK is mainly restricted to the medial half of the ventral aspect of the substantia nigra, while SP occupies its entire rostral-caudal and medial-lateral extents. Peptide-positive fibers vary in density from dense to light. There is very little overlap between the dorsal tier of the TH-positive neurons and the ENK or SP staining. The dorsal part of the peptide-immunoreactive area extensively overlaps with the TH-positive neurons of the ventral tier of cells. The ventral part of the peptide-positive area overlaps with the pars reticulata of the substantia nigra in which the TH-positive dendrites extend. The overlap between the neuropeptide fibers and the TH-positive cells of the ventral tier is not complete, with cells found both within and outside peptide-positive fiber networks. Three patterns of overlap emerge. In dorsal regions elongated cell clusters lie partially within and partially outside the dense peptide-positive fiber networks. In the ventral regions TH-positive cells are either completely embedded within peptide fibers or clusters of cells are present in peptide-free zones. These data suggest that specific peptidergic pathways differentially innervate the substantia nigra. TH cells which lie within or outside these fibers may reflect functionally different subsystems in the striatonigral pathways in the human.     

Identification of dopamine-containing cell bodies in the dorsal and median raphe nuclei of the rat brain using tyrosine hydroxylase immunochemistry

Using immunohistochemical methods with antibodies specific to tyrosine hydroxylase, we examined the distribution of dopaminergic cells in the dorsal and median raphe nucleus of the rat brain. Although dopamine-containing cell bodies were previously thought to be almost exclusively confined to the substantia nigra pars compacta, ventral tegmental area, and tuberoinfundibular system, we found numerous cell bodies which stained for tyrosine hydroxylase in the dorsal and median raphe nuclei.     

Compartmental distribution of ventral striatal neurons projecting to the mesencephalon in the rat.

The ventral striatum is characterized by an intricate neurochemical compartmentation that is reflected in the distribution of most of its afferent fiber systems. In the present study, the compartmental relationships of ventral striatal neurons projecting to the mesencephalon were studied by combining tract tracing with the immunohistochemical localization of leu-enkephalin. Injections of the retrograde tracer cholera toxin subunit B were placed at various sites in the ventral mesencephalon. The anterograde tracer Phaseolus vulgaris leucoagglutinin was injected in single compartments in the rostrolateral part of the nucleus accumbens. The projections from the ventral striatum to the dopaminergic cell groups in the ventral mesencephalon and those to the substantia nigra pars reticulata originate from distinct subpopulations of ventral striatal neurons that respect neurochemically defined compartmental boundaries. In the "shell" of the nucleus accumbens, neurons that project to the dopaminergic cell groups are located outside areas of high cell density and weak enkephalin immunoreactivity (ENK-IR). Rostrolaterally in the "core" of the nucleus accumbens, neurons inside large areas of strong ENK-IR surrounding the anterior commissure project to the dorsomedial part of the substantia nigra pars reticulata, whereas neurons outside these areas innervate the ventral tegmental area and/or the medial part of the substantia nigra pars compacta. By contrast, more caudally in the dorsal part of the nucleus accumbens and in the ventral part of the caudate-putamen, the relationships are reversed: neurons in- or outside small patches of strong ENK-IR project respectively to the pars compacta or the pars reticulata of the substantia nigra. Since the thalamic and cortical afferents of the ventral striatum are compartmentally ordered as well, the present results imply that through the ventral striatal compartments information from disparate combinations of cortical and thalamic sources may be conveyed to distinct mesencephalic targets. The component of the ventral striatomesencephalic system reaching the dopaminergic cell groups A10, A9, and A8 may modulate the dopaminergic input to virtually the entire striatum. The other component can, by way of the pars reticulata of the substantia nigra, participate in nigrothalamic and nigrotectal output pathways of the basal ganglia.     

Angiotensin II receptor binding associated with nigrostriatal dopaminergic neurons in human basal ganglia

In the human brain, receptor binding sites for angiotensin are found in the striatum and in the substantia nigra pars compacta overlying dopamine-containing cell bodies. In contrast, angiotensin-converting enzyme occurs in the substantia nigra pars reticulata and is enriched in the striosomes of the striatum. In this study, using quantitative in vitro autoradiography, we demonstrate decreased angiotensin receptor binding in the substantia nigra and striatum of postmortem brains from patients with Parkinson's disease. In the same brains the density of binding to angiotensin-converting enzyme shows no consistent change. We propose, from these results, that angiotensin receptors in the striatum are located presynaptically on dopaminergic terminals projecting from the substantia nigra. In contrast, the results support previous studies in rats demonstrating that angiotensin-converting enzyme is associated with striatal neurons projecting to the substantia nigra pars reticulata. These findings raise the possibility that newly emerging drugs that interact with the angiotensin system, particularly converting enzyme inhibitors and new nonpeptide angiotensin receptor blockers, may modulate the brain dopamine system.     

MPP(+) injection into rat substantia nigra causes secondary glial activation but not cell death in the ipsilateral striatum

Injection of MPP(+) into the substantia nigra causes extensive necrosis and anterograde degeneration of pars compacta dopaminergic neurons. We studied secondary effects in the ipsilateral striatum by examining dopaminergic terminals, signs of neuronal damage, and glial reactivity at 1, 2, 3, and 7 days after injection of MPP(+) into the substantia nigra. Dopaminergic terminals and uptake sites were evaluated with [(3)H]GBR-12935 binding and tyrosine hydroxylase immunoreactivity. Glial reaction was examined with markers of astrocytes and microglia. Stereology was used to evaluate any changes in neuronal density. Tyrosine hydroxylase immunoreactivity and [(3)H]GBR-12935 binding markedly decreased (74%) from days 2 to 7. Loss of dopaminergic terminals in the ipsilateral striatum was accompanied by an intense astroglial and, to a lesser extent, microglial reaction. However, no signs of cell damage, neuronal loss, or disruption of the blood-brain barrier were found in the striatum. Resident astroglial and microglial cells showed a morphological shift and notable changes in protein expression typical of glial reactivity, yet the presence of macrophage-like cells was not detected. This study shows that injection of MPP(+) in the substantia nigra causes a secondary reaction within the ipsilateral striatum involving the transformation of quiescent glia to reactive glia. It is suggested that stimuli derived from damaged dopaminergic terminals within the striatum are able to activate resident glia and that this glial transformation may promote repair and regeneration.     

Increase in immunohistochemical staining of GABAergic axons in the superior colliculus and thalamus of the rat following damage of the ipsilateral striatum and frontal cortex

The superior colliculus and ventromedial nucleus of the thalamus have been examined in rats following damage of the frontal cortex and underlying striatum with immunohistochemical staining using an antiserum directed against γ-aminobutyric acid (GABA). Following such lesions, at a time when the cell bodies of the neurones in the ipsilateral pars reticulata of the substantia nigra are known to be significantly enlarged, there is substantially more immunostaining of GABAergic fibres in both sites when compared with the contralateral side and with normal littermate control animals. The increase in immunoreactivity may indicate sprouting of the axons of the enlarging pars reticulata neurones or an increase in immunoreaction of existing fibres.     

Calbindin-D28k in the basal ganglia of patients with parkinsonism.

An immunohistochemical study was carried out to investigate the topographic distribution of calbindin-D28k in the human basal ganglia and substantia nigra and its alterations in patients with idiopathic Parkinson's disease (PD), parkinsonism-dementia complex on Guam, progressive supranuclear palsy, and striatonigral degeneration. In normal control subjects, calbindin-D28k immunoreactivity was identified in the medium-sized neurons and neuropil of the matrix compartment of the striatum, the woolly fiber arrangements of the globus pallidus, and the fiber structures of the pars reticulata of the substantia nigra. Calbindin-D28k expression in the basal ganglia of patients with PD and parkinsonism-dementia on Guam was not different from that of control subjects, suggesting that the matrical output pathway is spared in these disorders. In contrast, its disruption is inferred from the observed disorganization of woolly fibers in the globus pallidus of patients with progressive supranuclear palsy and the reduced calbindin-D28k reactivity in the putaminal matrix and the pars reticulata of the substantia nigra of subjects with striatal degeneration. Thus, our results indicate that calbindin-D28k is a useful marker for the projection system from the matrix compartment and that its expression is modified in patients with progressive supranuclear palsy and striatal degeneration.