Thalamic degeneration in MPTP-treated Parkinsonian monkeys: impact upon glutamatergic innervation of striatal cholinergic interneurons.

In both Parkinson's disease (PD) patients and MPTP-treated non-human primates, there is a profound neuronal degeneration of the intralaminar centromedian/parafascicular (CM/Pf) thalamic complex. Although this thalamic pathology has long been established in PD (and other neurodegenerative disorders), the impact of CM/Pf cell loss on the integrity of the thalamo-striatal glutamatergic system and its regulatory functions upon striatal neurons remain unknown. In the striatum, cholinergic interneurons (ChIs) are important constituents of the striatal microcircuitry and represent one of the main targets of CM/Pf-striatal projections. Using light and electron microscopy approaches, we have analyzed the potential impact of CM/Pf neuronal loss on the anatomy of the synaptic connections between thalamic terminals (vGluT2-positive) and ChIs neurons in the striatum of parkinsonian monkeys treated chronically with MPTP. The following conclusions can be drawn from our observations: (1) as reported in PD patients, and in our previous monkey study, CM/Pf neurons undergo profound degeneration in monkeys chronically treated with low doses of MPTP. (2) In the caudate (head and body) nucleus of parkinsonian monkeys, there is an increased density of ChIs. (3) Despite the robust loss of CM/Pf neurons, no significant change was found in the density of thalamostriatal (vGluT2-positive) terminals, and in the prevalence of vGluT2-positive terminals in contact with ChIs in parkinsonian monkeys. These findings provide new information about the state of thalamic innervation of the striatum in parkinsonian monkeys with CM/Pf degeneration, and bring up an additional level of intricacy to the consequences of thalamic pathology upon the functional microcircuitry of the thalamostriatal system in parkinsonism. Future studies are needed to assess the importance of CM/Pf neuronal loss, and its potential consequences on the neuroplastic changes induced in the synaptic organization of the thalamostriatal system, in the development of early cognitive impairments in PD.

Transgenic minipig model of Huntington's disease exhibiting gradually progressing neurodegeneration.

Recently developed therapeutic approaches for the treatment of Huntington's disease (HD) require preclinical testing in large animal models. The minipig is a suitable experimental animal because of its large gyrencephalic brain, body weight of 70-100 kg, long lifespan, and anatomical, physiological and metabolic resemblance to humans. The Libechov transgenic minipig model for HD (TgHD) has proven useful for proof of concept of developing new therapies. However, to evaluate the efficacy of different therapies on disease progression, a broader phenotypic characterization of the TgHD minipig is needed. In this study, we analyzed the brain tissues of TgHD minipigs at the age of 48 and 60-70 months, and compared them to wild-type animals. We were able to demonstrate not only an accumulation of different forms of mutant huntingtin (mHTT) in TgHD brain, but also pathological changes associated with cellular damage caused by mHTT. At 48 months, we detected pathological changes that included the demyelination of brain white matter, loss of function of striatal neurons in the putamen and activation of microglia. At 60-70 months, we found a clear marker of neurodegeneration: significant cell loss detected in the caudate nucleus, putamen and cortex. This was accompanied by clusters of structures accumulating in the neurites of some neurons, a sign of their degeneration that is also seen in Alzheimer's disease, and a significant activation of astrocytes. In summary, our data demonstrate age-dependent neuropathology with later onset of neurodegeneration in TgHD minipigs.

[Ultrastructural changes of myelinated fibers in the brain in continuous and attack-like paranoid schizophrenia]. / Ul'trastrukturnye izmeneniya mielinovykh volokon v golovnom mozge pri nepreryvnotekushchei i pristupoobraznoi paranoidnoi shizofrenii.

AIM: Previously the authors have reported the ultrastructural pathology of myelinated fibers (MF) in the brain in schizophrenia. The aim of the present study was to compare the effect of disease course on ultrastructural changes of MF. MATERIAL AND METHODS: Postmortem electron microscopic morphometric study of MF was performed in the prefrontal cortex, caudate nucleus and hippocampus in 19 cases of paranoid schizophrenia. Fourteen cases of continuous schizophrenia, 5 cases of attack-like schizophrenia and 25 normal matched control cases were studied. The proportion (percentage) of pathological MF was estimated in the prefrontal cortex, layer 5, CA3 area of hippocampus, pyramidal layer, and in the head of the caudate nucleus. RESULTS: The percentage of MF having axonal atrophy and swelling of periaxonal oligodendrocyte process was significantly higher in both continuous and attack-like schizophrenia in all brain structures studied as compared to the control group. In the hippocampus and caudate nucleus, this parameter was increased significantly in attack-like schizophrenia as compared to continuous schizophrenia. In the prefrontal cortex. The percentage of the pathological MF having signs of deformation and destruction of myelin sheaths increased significantly only in continuous schizophrenia as compared to the control group. CONCLUSION: MF pathology is similar in attack-like and continuous paranoid schizophrenia but differ by the degree of severity of pathological MF. Abnormalities in MF contribute to the disconnectivity between the prefrontal cortex, caudate nucleus and hippocampus.

A novel, fully automated, observer-independent program for semiquantifying striatal 123I-FP-CIT uptake / Un nuevo programa, totalmente automático e independiente del observador para semi-cuantificar la captación estriatal de 123I-FP-CIT

Objective: To describe and validate a novel, fully automated program specifically designed for the semi- quantification of striatal 123I-FP-CIT uptake using volumes of interest (VOI) analysis. Material and methods: The proposed algorithm is based on a template that mimics the striatal 123 I-FP-CIT uptake in a healthy subjects, derived from defined anatomical VOIs available from WFU PickAtlas. Four SPECT studies of the anthropomorphic Alderson phantom filled with variable radioactive concentrations were acquired for the experimental validation. Experimental SPECT images were spatially normalized with respect to the previously created template. The binary VOIs corresponding to left caudate and puta- men and right caudate and putamen, which were used to construct the template, were projected onto the experimental images to obtain the counts for these regions. To minimize the partial volume effect, a percentage of the voxels in these regions (threshold), rather than all of them, was used. A binary occipital VOI was used to quantify the non-specific uptake. Experimental binding potentials (BPs) were calculated from the counts in these regions. True BPs were calculated from aliquots taken from the solutions used to fill the phantom. Results: There were statistically significant differences in the experimental BP values (p < 0.002) accord- ing to the percentage of voxels used. A highly significant correlation was achieved between true and experimental BP values, regardless of the percentage of voxels included for quantification. Conclusions: Our novel, observer-independent program automatically performs the semiquantification of striatal 123I-FP-CIT uptake in experimental studies (AU)

Objetivos: Describir y validar un nuevo software, totalmente automático, específicamente diseñado para semicuantificar la captación estriatal de 123I-FP-CIT usando volúmenes de interés (VOIs). Material y métodos: El algoritmo propuesto se basa en una plantilla que remeda la captación estriatal de 123I-FP-CIT en un sujeto sano, obtenida a partir de VOIs anatómicos definidos en WFU PickAtlas. Para la validación experimental de este algoritmo se adquirieron 4 estudios SPECT del maniquí antropomórfico Alderson llenado con concentraciones radioactivas variables. Las imágenes SPECT experimentales se normalizaron espacialmente respecto a la plantilla creada. Los VOIs binarios correspondientes a núcleo caudado y putámen derechos e izquierdos, utilizados para disen ̃ar la plantilla, se proyectaron sobre las imágenes experimentales para obtener las cuentas en estas regiones. Para minimizar los efectos de volumen parcial se utilizó un porcentaje de vóxeles, en vez de utilizar todos los vóxeles contenidos en estos VOIs. Se ha utilizado un VOI binario situado en región occipital para cuantificar la unión no específica. Los potenciales de unión (BPs) experimentales se calcularon a partir de las cuentas obtenidas en estas regiones. Los BPs reales se calcularon a partir de alícuotas tomadas de las soluciones utilizadas para llenar el maniquí. Resultados: Hubo diferencias estadísticamente significativas en los BPs experimentales en función del porcentaje de vóxeles utilizados para la cuantificación (p < 0.002). Se alcanzó una alta correlación entre los BPs reales y los experimentales, independientemente del porcentaje de vóxeles utilizados para la cuantificación. Conclusiones: Este nuevo programa automático e independiente del observador realiza la semicuantificación de la captación estriatal de 123I-FP-CIT en estudios experimentales (AU)

Ultrastructural Changes of Caudate Nucleus in Mice Chronically Treated with Manganese.

Manganese (Mn) is able to cross the blood-brain barrier and induces functional and structural alterations during the intoxication by this metal. Therefore, the effects of chronic administration of Mn in the caudate nucleus of mice were evaluated by electron microscopy. Male albino mice were injected intraperitoneally with MnCl2 (5 mg/kg/d) 5 d per week during 9 weeks. The control group received only 0.9% of NaCl solution. The caudate nuclei were extracted and subsequently processed to be observed on a conventional transmission electron microscope at 2, 4, 6, and 9 weeks after treatment. A high percentage of vacuolated and swollen mitochondria were found throughout all the analyzed periods. Myelin disarrangement and ultrastructural alterations related to edema were observed increased in Mn-treated mice at week 9. Granular degeneration of myelin at week 9 accompanied with deposition of electron dense granules in the neuropil was also observed. Edema in neuropil and glial cells was detected from week 2 to week 9 accompanied by swollen mitochondria. Neuronal bodies, synaptic terminals, and perivascular cells were found swollen. Decreased electron density in postsynaptic areas and decreased and dispersed synaptic vesicles in presynaptic areas were noted in Mn-treated animals. Some neurons from Mn-treated mice showed cisternae dilation of the Golgi apparatus. These results suggest that Mn-treatment produces structural alterations in the caudate nucleus that could be responsible for some of the neurotoxic effects of this metal.

[Organization of the projections of the substructures of deep mesencephalic nucleus to the striatum in the dog brain].

Method of retrograde axonal transport of horseradish peroxidase was used to study the organization of the projections of the individual substructures of the deep mesencephalic nucleus complex to the functionally diverse regions of striatal structures of the dog brain (n=20). It was shown that the projection fibers of the neurons of the nucleus profundus mesencephali were directed to the ventro-lateral segment of the nucleus caudatus and the ventral segment of the putamen. The dorsal segment of the putamen obtains the fibers from the neurons of the nucleus cuneiformis, while the lateral segment of the nucleus accumbens received them from the neurons of the nucleus subcuneiformis. The possible pathways for conduction of the functionally diverse information and its integration in the investigated projection systems are discussed.

Regional differences in human ependymal and subventricular zone cytoarchitecture are unchanged in neuropsychiatric disease.

Much work has focused on the possible contribution of adult hippocampal neurogenesis to neuropsychiatric diseases. The hippocampal subgranular zone and the other stem cell-containing neurogenic niche, the subventricular zone (SVZ), share several cytological features and are regulated by some of the same molecular mechanisms. However, very little is known about the SVZ in neuropsychiatric disorders. This is important since it surrounds the lateral ventricles and in schizophrenia ventricular enlargement frequently follows forebrain nuclei shrinkage. Also, adult neurogenesis has been implicated in pharmacotherapy for affective disorders and many of the molecules associated with neuropsychiatric disorders affect SVZ biology. To assess the neurogenic niche, we examined material from 60 humans (Stanley Collection) and characterized the cytoarchitecture of the SVZ and ependymal layer in age-, sex- and post mortem interval-matched controls, and patients diagnosed with schizophrenia, bipolar illness, and depression (n = 15 each). There is a paucity of post mortem brains available for study in these diseases, so to maximize the number of possible parameters examined here, we quantified individual sections rather than a large series. Previous work showed that multiple sclerosis is associated with increased width of the hypocellular gap, a cell-sparse region that typifies the human SVZ. Statistically there were no differences between disease groups and controls in the width of the hypocellular gap or in the density of cells in the hypocellular gap. Because ventricular enlargement in schizophrenia may disrupt ependymal cells, we quantified them, but observed no difference between diagnostic groups and controls. There are significant differences in the prevalence of neuropsychiatric illness between the sexes. Therefore, we looked for male versus female differences, but did not observe any in the parameters quantified. We next turned to a finer spatial resolution and asked if there were differences amongst the disease groups in dorsal ventral subdivisions of the SVZ. Similar to when we treated the SVZ as a whole, we did not find such differences. However, compared to the dorsal SVZ, the ventral SVZ had a wider hypocellular gap and more ependymal cells in all four groups. In contrast, cell density was similar in dorsal ventral subregions of the SVZ hypocellular gap. These results show that though there are regional differences in the SVZ in humans, neuropsychiatric disorders do not seem to alter several fundamental histological features of this adult neurogenic zone.

[Fusion of brain neurons in rat embryos].

Syncytial interneuronal connections were studied in the sensomotor cortex and caudate nucleus of twenty 14-22 day rat embryos. It was shown that with the extremely weak development of glial processes, many neuronal bodies and their processes were in the direct contact with each other. The contacting membranes in these areas formed oblong and dot-like contacts resembling gap and tight junctions. As a result, the intercellular cleft experienced varicose-like deformations. In the area of contacts, barely visible membrane pores were formed that broadened to form large perforations. The perforation margins presented the rounded shape of fused plasma membranes of adjacent neurons. Inside the perforations, residual vesicular membranous bodies were formed. The areas of the paired membranes between perforations were fragmented, thus increasing the number of residual vesicles, until the neurons fused with each other completely by unifying the neuroplasm of contacting cells. The results of these studies suggest that that the fusion of neurons in vertebrate brain cortex and brainstem nuclei could occur not only in pathology, but also in normal animals at the stage of embryonic development.

[Structural basis for the inhibitory function of the parietal cortex efferent systems].

Relative quantitative distribution of all the associative and descending efferent fibers and the ultrastructural organization of the terminals of the parietal cortex areas 5 and 7 in the caudate (NC) and red nucleus (NR) in the cat were analyzed after a local, pointed destruction of the cortex of these areas. The maximal numbers of the associative fibers were found to project to the fundus areas of the motor cortex and to the area of Clare-Bishop; moderate projections were detected to the areas 31, 19 and single degenerating fibers were registered in the areas 1,2, 3a, 3b, 30, and 23. The descending efferents were maximally projecting to NC, NR, reticular nuclei of the thalamus, midbrain, and pons, in all of which, according to the immunocytochemical studies, GABA-ergic terminals are prevalent. On the basis on the electron microscopical studies, it was suggested that the influence of the parietal cortex is mediated by the axo-spinal synapses of the medium shortaxonal spiny cells of the dorsolateral part of NC caput and by the axo-dendritic synapses of Golgi II cells of the parvocellular part of NR. On the basis of the maximal involvement of the fundus areas of the motor cortex, as well as of the inhibitory subcortical (NC) and stem nuclei (NR, reticular nuclei of the thalamus, midbrain, and nuclei pontis), it is suggested that these structures serve as the morphological substrates for the realization of the inhibitory, integrative function of the parietal cortex.

Mitochondria in the striatum of subjects with schizophrenia.

OBJECTIVES: Schizophrenia is a severe mental illness that manifests pathology in many brain regions, including the striatum. Among the abnormalities in schizophrenia are those related to mitochondria. The present study sought to determine whether the number of mitochondria was affected at the level of the synapse. METHODS: Human postmortem striatum from schizophrenia subjects and controls was examined at the ultrastructural level. The density of mitochondria and synapses were tabulated using stereology. RESULTS: There were similar overall numbers of mitochondria in the caudate nucleus and putamen of schizophrenia subjects vs. controls, but a differential distribution of existing mitochondria. Schizophrenia subjects had 26?30% fewer mitochondria per synapse compared to controls. This may contribute to the pathophysiology of the illness, may be a medication effect, or an adaptive response to normalize the high number of striatal synapses we have previously found. The higher density of mitochondria in dendrites in the caudate nucleus in certain subgroups of schizophrenia vs. controls (>34%) may be related to more synaptic inputs. CONCLUSIONS: The role of mitochondria in the various symptoms of schizophrenia is still unclear. A comparison of schizophrenia subjects with differing symptoms or treatment response might shed light on whether differences in mitochondrial density are abnormal or adaptive.

Lrrk2 localization in the primate basal ganglia and thalamus: a light and electron microscopic analysis in monkeys.

The Leucine Rich Repeat Kinase-2 (LRRK2) gene is a common mutation target in Parkinson's disease (PD), but the cellular mechanisms by which such mutations underlie the pathophysiology of PD remain poorly understood. Thus, to better characterize the neuronal target sites of LRRK2 mutations in the primate brain, we studied the cellular and ultrastructural localization of Lrrk2 immunoreactivity in the monkey basal ganglia. As previously described, the monkey striatum was the most enriched basal ganglia structure in Lrrk2 labeling. Both projection neurons and parvalbumin-containing GABAergic interneurons displayed Lrrk2 immunoreactivity. At the electron microscopic level, striatal Lrrk2 labeling was associated predominantly with dendritic shafts and subsets of putative glutamatergic axon terminals. At the pallidal level, moderate cellular Lrrk2 immunostaining was found in the external globus pallidus (GPe), while neurons in the internal globus pallidus (GPi) were devoid of Lrrk2 immunoreactivity. Strong labeling was associated with cholinergic neurons in the nucleus basalis of Meynert. Midbrain dopaminergic neurons in the primate substantia nigra pars compacta (SNc) and ventral tegmental area harbored a significant level of Lrrk2 labeling, while neurons in the subthalamic nucleus were lightly immunostained. Most thalamic nuclei were enriched in Lrrk2 immunoreactivity, except for the centromedian nucleus that was completely devoid of labeling. Thus, Lrrk2 protein is widely distributed in the monkey basal ganglia, suggesting that gene mutations in PD may result in multifarious pathophysiological effects that could impact various target sites in the functional circuitry of the primate basal ganglia.

Time-dependent exposure of nicotine and smoke modulate ultrasubcellular organelle localization of dopamine D1 and D2 receptors in the rat caudate-putamen.

The correlation of the subcellular localization of dopamine D(1) and D(2) receptors (DA D(1) R, DA D(2) R) with nicotine addiction has not been studied. We demonstrated the ultrasubcellular organelle localization of DA D(1) and D(2) Rs in the caudate-putamen (CPu) area of rat brain in vivo exposed to nicotine (3 mg/day; oral) and passive cigarette smoking (500 ml each; 3 times/day) for 1, 4, and 12 weeks, respectively. Our results revealed DA D(1) R localization in the presynaptic and postsynaptic dendrites, endocytic vesicles, and secretory granules, and DA D(2) R localization in the presynaptic dendrites and vesicles. DA D(1) R immunogold particles were highly decreased in the secretory granules of CPu, and increased in the postsynaptic area and vesicles after prolonged nicotine and smoking exposures, suggesting the strong influence of long time smoking and nicotine exposures on DA D(1) R subcellular organelle localization. DA D(2) R immunoreactivity was comparatively less changed than that of the DA D(1) R. Western blot analysis also showed the differential expression of DA D(1) and D(2) R proteins upon nicotine and smoking exposures as compared to the untreated controls. Taken together, the results for the first time suggests the execution of addictive behavior of nicotine through modulation of mesolimbic dopaminergic system targeting subcellular organelle of DA D(1) and D(2) Rs in the CPu of adult rat brain that may lead to novel therapeutic approaches related to nicotine's neuropsychological disorders including drug addiction.

The role of oligodendrocyte pathology in schizophrenia.

Neuroimaging and microarray studies provide evidence for myelin and oligodendrocyte abnormalities in schizophrenia (SZ). Electron microscopy demonstrated dystrophy, necrosis and apoptosis of oligodendrocytes, the most severely affected cells in SZ. The proportion of myelinated fibres with atrophy of axon and swelling of periaxonal oligodendrocyte processes increased significantly in the prefrontal cortex (PFC), caudate nucleus and hippocampus in SZ compared to controls. Morphometry showed a deficit of oligodendrocytes in the PFC and in adjacent white matter, lower number of oligodendroglial satellites of pyramidal neurons and a loss of pericapillar oligodendrocytes in the PFC in SZ compared to normal controls. A lowered number of oligodendrocytes in the PFC was also found in mood disorders. These data provide evidence for altered oligodendrocyte-axon, oligodendrocyte-neuron and oligodendrocyte-capillar interactions in SZ brains suggesting a key role of damage and loss of oligodendrocytes in altered neuronal connectivity and in atrophy of neurons in SZ.

[The protective effect of nicotine on dopaminergic neuron of Parkinson's disease mice].

AIM: To investigate the protective effect of nicotine on dopaminergic neurons and its mechanisms in mice with Parkinson's disease (PD) induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). METHODS: C57BL/6J mice were injected with MPTP for 8 days to establish PD model. Nicotine was given for 10 days in the pretreatment group. Animals were examined behaviorally with the pole test and traction test. Tyrosine hydroxylase (TH) and gamma-aminobutyric acid (GABA) were investigated by the immunocytochemistry (ICC) method. The ultrastructural changes of caudate nucleus(CN) were observed by electron microscope. RESULTS: The results showed that pretreatment nicotine could improve the dyskinesia of PD mice markedly. Simultaneously, TH (P < 0.01) neurons and GABA (P < 0.05) neurons were much more in the pretreatment group when compared with those in the model group. The ultrastructural injury of the pretreatment group was also ameliorated. CONCLUSION: Nicotine has a protective effect on the dopaminergic neurons in the MPTP-treated mice.

Synaptic differences in the patch matrix compartments of subjects with schizophrenia: a postmortem ultrastructural study of the striatum.

The striatum processes motor, cognitive, and limbic circuitry. Striatal patch and matrix compartments are organized differently in many aspects including connectivity. Abnormalities in either compartment could have different functional consequences. The present study compares the synaptic organization in the patches and matrix in subjects with schizophrenia (SZ, n = 14) versus normal controls (NC, n = 8). Postmortem striatal tissue was processed for calbindin immunocytochemistry to identify the patch versus matrix compartments, prepared for electron microscopy, and analyzed using stereology. Several synaptic changes were observed in the SZ subjects vs. NCs including a higher density of cortical-type synapses in the putamen patch (44% higher) and in the caudate matrix (36% higher) in SZ cases on typical antipsychotic drugs. These changes appeared to be normalized rather than caused by treatment. The abnormal connectivity may represent a failure of normal synaptic pruning and may play a role in limbic or cognitive dysfunction in schizophrenia.

Bromocriptine treatment in a murine Parkinson's model: ultrastructural evaluation after dopaminergic deafferentation.

The objective of this article was to identify the effects of bromocriptine on the ultrastructure of the caudate nucleus in rats with a 6-hydroxidopamine (6-OHDA) unilateral lesion of the substantia nigra pars compacta. Eighteen Wistar male rats were stereotactically lesioned with 6-OHDA (n=12), or sham lesioned (n=6). Two days after rotational behavior was tested, and 2 days later, 6 rats were treated with 0.3 mg/Kg bromocriptine orally for a month and 6 rats were kept for the same time without treatment. The neuropile of the sham operated and bromocriptine-treated rats was well preserved contrary to the non-bromocriptine-treated rats. Also, it was found that there was a significant difference in the number of synaptic endings with edema in caudate of bromocriptine-treated rats compared with non-treated rats; however, the size of the synaptic endings were different to those found in the sham lesioned rats. Also, as in the sham lesioned group, the bromocriptines showed more synaptic contacts with dendritic spines contrasting to the non-treated group. The results suggest that bromocriptine possesses antioxidant properties because it decreased the ultrastructural alterations after 6-OHDA lesion.

Activity-regulated cytoskeleton-associated protein Arc is targeted to dendrites and coexpressed with mu-opioid receptors in postnatal rat caudate-putamen nucleus.

Dendritic expression of the activity-regulated cytoskeleton-associated protein (Arc) is dramatically enhanced by increased synaptic activity in adult brain. We used immunocytochemical electron microscopy to determine whether the subcellular localization of Arc in developing dendrites corresponds to the peak period of synaptogenesis in the postnatal rat caudate-putamen nucleus (CPN). The distribution was compared with that of mu-opioid receptors (MORs), whose localization in dendritic spines closely parallels excitatory synapse formation during postnatal development (Wang et al. [2003] Neuroscience 118:695-708). Sections were processed for immunocytochemical detection of antisera against Arc or MORs at the beginning (postnatal day 15; P15) and the end (P30) of the peak period of synaptogenesis in rat CPN. At P15, immunolabeling for Arc showed a punctate distribution in the cytoplasm of dendritic shafts, some of which was associated with polyribosomes. In some spiny dendrites, Arc immunoreactivity was more intensely localized in putative spines than in their parental dendrites, whereas, in other spiny dendrites, Arc labeling was restricted in the shafts. Many dendritic shafts and spines also showed immunoreactivity for MORs, although dually labeled spines were less numerous than the shafts. At P30, the proportion of singly and dually labeled spines significantly increased from 2.0% to 7.5% and from 9.5% to 21%, respectively. Arc labeling in spines was more detectable beneath the postsynaptic density or at extrasynaptic sites on the plasma membrane. Our results suggest a correlation between Arc expression in dendritic spines during postnatal development and the onset of synaptogenesis in opioid-responsive neurons in the rat CPN.

Ultrastructural localization of delta-opioid receptors in the rat caudate-putamen nucleus during postnatal development: relation to synaptogenesis.

During development, delta-opioid receptors (DORs) in the rat caudate-putamen nucleus (CPN) appear later than mu-opioid receptors (MORs), whose developmental pattern specifically relates to synaptogenesis. We used electron microscopic immunocytochemistry to determine whether there are also age-related changes in subcellular localization of DORs in the rat CPN. Sections from postnatal day (P) 0-P30 and adult dorsomedial CPN were immunogold-silver labeled to examine the plasmalemmal and cytoplasmic distribution of these receptors. In addition, immunoperoxidase labeling was used to determine the numerical density of synapses relative to DOR-labeled profiles. Immunolabeling for DOR was undetectable at P0, light at P5, and dense from P10 onward. The labeling during P5-P10 was mainly localized in somatodendritic profiles but also was readily seen in axon terminals, most of which formed asymmetric synapses with dendrites. From P15, a few immunogold particles were seen in contact with postsynaptic densities in spines, and the proportion of these particles significantly increased in P30 and adult CPN. Other particles were localized in the cytoplasm of dendrites and terminals without significant age-related changes. Stereological analysis showed that compared with labeled dendritic shafts and spines, labeled axon terminals have a closer correlation with synapse formation. These results are in marked contrast with MORs, which show an age-related increase in association with dendritic plasma membrane and a good correlation in the developmental pattern of MOR-labeled spines with synapse formation (Wang et al. [2003] Neuroscience 118:695-708). Together, our results suggest receptor-type specific roles for endogenous opioids acting at both pre- and postsynaptic sides in the developing CPN.

Postnatal development of mu-opioid receptors in the rat caudate-putamen nucleus parallels asymmetric synapse formation.

The mu-opioid receptor (MOR) in the caudate-putamen nucleus (CPN) appears early during prenatal development, and shows a patch-like distribution throughout the postnatal period and adulthood. In the adult rat CPN, neurons in patch compartments receive glutamatergic excitatory input mainly from the cortex through synapses onto spines, many of which express MORs. Thus, MOR expression in spines may be related to corticostriatal synaptogenesis. We used electron microscopic immunocytochemistry to determine potential age-dependent changes in the distribution pattern of MOR during postnatal synaptogenesis in the rat CPN. Immunogold-silver labeling revealed that the dendritic plasmalemmal density of MOR at postnatal day (P) 0 was significantly lower than, but after P10 was similar to, that of adult. In contrast, such age-dependent changes were not observed in axon terminals. Stereological analysis of immunoperoxidase labeling for MOR showed a good correlation in the developmental numerical densities of synapses with MOR-labeled spines and those of total asymmetric axospinous synapses, linear correlation coefficient r=0.99. Synapses with MOR-labeled dendrites, however, had a low correlation with axodendritic synapses (r=0.61), and synapses with MOR-labeled terminals showed no correlation with axospinous and axodendritic synapses (r=0.19). These results provide ultrastructural evidence that the targeting of MOR on the plasma membrane of dendrites and spines parallels the peak period of synaptogenesis during the third postnatal week in the rat CPN. Thus, the postnatal spatiotemporal expression pattern of MOR appears to match the functional maturation of corticostriatal glutamate transmission.

The ultrastructural organization of the patch matrix compartments in the human striatum.

The mammalian striatum is a heterogeneous structure characterized by striosomes and matrix. The synaptic organization of the striatum has been described previously in various mammalian species including human; however, potential ultrastructural differences in striosomal organization have not been well studied. Samples (n = 7) of striatal tissue were obtained from the Maryland Brain Collection (mean age, 37.7 +/- 9.4 years; and mean PMI, 5.3 +/- 1.4 hours). Tissue was prepared for calbindin immunocytochemistry to identify striosomal (patch) and extrastriosomal matrix (matrix) compartments and subsequently prepared for electron microscopy. Synaptic density was determined, using stereologic methods, for all synapses combined and for various subsets of synapses such as asymmetric, symmetric, axospinous, axodendritic, and perforated in the patch and matrix of the caudate (CP, CM) and putamen (PP, PM). An ANOVA revealed significant between-group (CP, CM, PP, PM) differences (P < 0.05) for the following types of synapses: total combined, asymmetric, axospinous, and asymmetric axospinous. Each of these four types was significantly increased in density in the CP vs the PP, whereas the matrix (CM vs PM) showed no significant differences in density in these or other synapses. In the caudate (CP vs CM), the synaptic density of the types of synapses studied did not vary significantly between the patch and the matrix. In the putamen, the matrix (PM) had higher synaptic densities than that of the patches (PP) for total synapses, symmetric dendritic, and perforated. These data show that the patch and matrix compartments are heterogeneous at the ultrastructural level, imparting another level of complexity to the striatum-a fact that should be taken into consideration when studying diseases of this brain region at the electron microscopic level.