Anatomical localization of Cav3.1 calcium channels and electrophysiological effects of T-type calcium channel blockade in the motor thalamus of MPTP-treated monkeys.

Conventional anti-Parkinsonian dopamine replacement therapy is often complicated by side effects that limit the use of these medications. There is a continuing need to develop nondopaminergic approaches to treat Parkinsonism. One such approach is to use medications that normalize dopamine depletion-related firing abnormalities in the basal ganglia-thalamocortical circuitry. In this study, we assessed the potential of a specific T-type calcium channel blocker (ML218) to eliminate pathologic burst patterns of firing in the basal ganglia-receiving territory of the motor thalamus in Parkinsonian monkeys. We also carried out an anatomical study, demonstrating that the immunoreactivity for T-type calcium channels is strongly expressed in the motor thalamus in normal and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys. At the electron microscopic level, dendrites accounted for >90% of all tissue elements that were immunoreactive for voltage-gated calcium channel, type 3.2-containing T-type calcium channels in normal and Parkinsonian monkeys. Subsequent in vivo electrophysiologic studies in awake MPTP-treated Parkinsonian monkeys demonstrated that intrathalamic microinjections of ML218 (0.5 µl of a 2.5-mM solution, injected at 0.1-0.2 µl/min) partially normalized the thalamic activity by reducing the proportion of rebound bursts and increasing the proportion of spikes in non-rebound bursts. The drug also attenuated oscillatory activity in the 3-13-Hz frequency range and increased gamma frequency oscillations. However, ML218 did not normalize Parkinsonism-related changes in firing rates and oscillatory activity in the beta frequency range. Whereas the described changes are promising, a more complete assessment of the cellular and behavioral effects of ML218 (or similar drugs) is needed for a full appraisal of their anti-Parkinsonian potential.

Decreased mitochondrial bioenergetics and calcium buffering capacity in the basal ganglia correlates with motor deficits in a nonhuman primate model of aging.

Altered mitochondrial function in the basal ganglia has been hypothesized to underlie cellular senescence and promote age-related motor decline. We tested this hypothesis in a nonhuman primate model of human aging. Six young (6-8 years old) and 6 aged (20-25 years old) female Rhesus monkeys (Macaca mulatta) were behaviorally characterized from standardized video records. Additionally, we measured mitochondrial bioenergetics along with calcium buffering capacity in the substantia nigra and putamen (PUT) from both age groups. Our results demonstrate that the aged animals had significantly reduced locomotor activity and movement speed compared with younger animals. Moreover, aged monkeys had significantly reduced ATP synthesis capacity (in substantia nigra and PUT), reduced pyruvate dehydrogenase activity (in PUT), and reduced calcium buffering capacity (in PUT) compared with younger animals. Furthermore, this age-related decline in mitochondrial function in the basal ganglia correlated with decline in motor function. Overall, our results suggest that drug therapies designed to enhance altered mitochondrial function may help improve motor deficits in the elderly.

[On the question of the organization of brain function: cortical associations, «disconnection¼ syndrome and higher brain functions].

The review considers the structural/functional brain organization, the disturbance of which is accompanied by the development of cognitive and behavioral disorders. The significance of the disruption of parallel circuits connecting frontal lobes with subcortical structures (the basal ganglia, thalamus, cerebellum) is highlighted. This disruption is clinically described as "disconnection" syndrome. The associations between the basal ganglia and the cortex of the large cerebral hemispheres responsible for motor, cognitive and emotional/behavioral functions do not restricted to these spheres and is characteristic not only of frontal brain areas. There are circuits connecting other brain compartments and the basal ganglia that provide perception, and are involved in decision making on the basis of input information of different modalities.The improvement of understanding of the pathophysiology and neurochemistry of these structures opens new possibilities for selective action on some or other circuit to achieve the best therapeutic result.

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.

Ultrastructural localization of calcyon in the primate cortico-basal ganglia-thalamocortical loop.

Recent observations suggest that calcyon, a novel single transmembrane protein implicated in schizophrenia and attention-deficit/hyperactivity disorder, regulates clathrin-mediated endocytosis in brain. To explore the role of calcyon in neurotransmission, we investigated its distribution in the neuropil of the primate prefrontal cortex (PFC), striatum (STR) and mediodorsal thalamic nucleus (MD), three brain regions implicated in these neuropsychiatric disorders. Calcyonimmunoreactivity revealed by immunoperoxidase technique, was localized in both pre- and postsynaptic structures including axons, spines and dendrites, as well as myelinated fibers and astroglial processes in all the three brain regions. The morphological diversity of immunopositive boutons suggest that in addition to glutamatergic, calcyon could regulate GABAergic as well as monoaminergic neurotransmission. Consistent with the role of calcyon in endocytosis, calcyon-immunoreactivity was rarely found at the synaptic membrane specializations proper, although it was present in distal compartments of neuronal processes establishing synapses. Given the widespread upregulation of calcyon in schizophrenic brain, these findings underscore a potential association with deficits in a range of neurotransmitter systems in the cortico-basal ganglia-thalamic loop.

Ultrastructural localization of parkin in the rat brainstem, thalamus and basal ganglia.

The parkin gene encodes a 52 kd putative E3 ubiquitin-protein ligase involved in an autosomal recessive form of early onset parkinsonism. Parkin ultrastructural localization was studied by immunohistochemistry in the adult rat brain and in a parkin inducible PC12 cell line (HS22). In the rat brain, parkin immunoreactivity was detected in neuronal and glial cell bodies and in nerve processes. In the neurons, it was mostly localized on the periphery of large vesicles, some rare mitochondria and endoplasmic reticulum in the cell bodies, and on the periphery of large vesicles in the dendrites and terminals of the neurons. In addition, parkin immunoreactivity was also found around synaptic vesicles in the presynaptic elements of some axons. In HS22 cells over-expressing parkin, the distribution of the protein was similar to that observed in the perikarya of the labeled neurons.

Light and electron microscopic evidence for projections from the thalamic nucleus rotundus to targets in the basal ganglia, the dorsal ventricular ridge, and the amygdaloid complex in a lizard.

To elucidate the organization and evolution of the tectorotundotelencephalic pathways in birds and reptiles, we reinvestigated at both light and electron microscopic levels the efferent projections of nucleus rotundus in a lizard, using the sensitive tracer biotinylated dextran amine. Our results indicate that nucleus rotundus projects to targets in the basal ganglia (lateral parts of striatum and olfactory tubercle and possibly the globus pallidus), the anterior dorsal ventricular ridge (ADVR), and the amygdaloid complex (the central and possibly lateral amygdaloid nuclei). In these targets, the rotundal axon terminals establish asymmetric, presumably excitatory synaptic contacts, usually with dendrites of local cells. In the ADVR, the rotundal projection terminates in two separate radial regions showing distinct cytoarchitecture: 1) a dorsolateral region that extends radially from the dorsolateral ADVR ventricular surface to the ventral part of the lateral cortex and 2) the lateral part of a ventromedial region that extends radially from the dorsomedial and medial ADVR ventricle to a superficial area interposed between the dorsolateral ADVR and the striatum. These two ADVR regions have different connections with the thalamus and telencephalon, which suggests that they may be involved in different degrees of integration. Our study also suggests that the rotundal projection to the ventromedial ADVR field of lizards may be comparable to the rotundoectostriatal/periectostriatal projection of birds. The connections and pathways involving nucleus rotundus suggest that this nucleus conveys visual information which may play a role in visuomotor, emotional, and visceral functions.

The glutamate-enriched cortical and thalamic input to neurons in the subthalamic nucleus of the rat: convergence with GABA-positive terminals.

Neurons of the subthalamic nucleus play a key role in the normal physiology and the pathophysiology of the basal ganglia. In order to understand better how the activity of subthalamic neurons and hence the output of the basal ganglia are controlled, we have reexamined the topography and examined in detail the synaptology and neurochemical nature of the two major excitatory projections to the subthalamic nucleus, that from the cortex and from the parafascicular nucleus of the thalamus. The approach was to use anterograde neuronal tracing and postembedding immunocytochemistry for amino acid transmitters. In confirmation of previous findings the cortical and thalamic projections were topographically organized, although the topography was more finely organized, and the projections more extensive, than previously demonstrated. Cortical and thalamic terminals made asymmetrical synaptic contacts with the dendrites and spines of subthalamic neurons. The thalamic terminals contacted larger postsynaptic targets, and therefore presumably more proximal regions of subthalamic neurons, than did the cortical terminals. Quantitative analysis of the postembedding immunolabelled sections revealed that the cortical and thalamic terminals were significantly enriched in glutamate-immunoreactivity when compared to identified gamma-aminobutyric acid (GABA)-positive terminals, supporting physiological studies that suggest that these projections use glutamate as their neurotransmitter. In addition a small population of nonanterogradely labelled terminals that formed asymmetrical synapses and were immunopositive for GABA were identified. A larger population of terminals that formed symmetrical synapses were also immunopositive for GABA and were probably derived from the globus pallidus. The latter type of terminal was found to make convergent synaptic input with cortical or thalamic terminals on the dendrites and spines of subthalamic neurons, indicating that the "indirect pathways" by which information flows through the basal ganglia converge at the level of individual neurons in the subthalamic nucleus.

GABAA-receptor heterogeneity in the adult rat brain: differential regional and cellular distribution of seven major subunits.

GABAA-receptors display an extensive structural heterogeneity based on the differential assembly of a family of at least 15 subunits (alpha 1-6, beta 1-3, gamma 1-3, delta, rho 1-2) into distinct heteromeric receptor complexes. The subunit composition of receptor subtypes is expected to determine their physiological properties and pharmacological profiles, thereby contributing to flexibility in signal transduction and allosteric modulation. In heterologous expression systems, functional receptors require a combination of alpha-, beta-, and gamma-subunit variants, the gamma 2-subunit being essential to convey a classical benzodiazepine site to the receptor. The subunit composition and stoichiometry of native GABAA-receptor subtypes remain unknown. The aim of this study was to identify immunohistochemically the main subunit combinations expressed in the adult rat brain and to allocate them to identified neurons. The regional and cellular distribution of seven major subunits (alpha 1, alpha 2, alpha 3, alpha 5, beta 2,3, gamma 2, delta) was visualized by immunoperoxidase staining with subunit-specific antibodies (the beta 2- and beta 3-subunits were covisualized with the monoclonal antibody bd-17). Putative receptor subtypes were identified on the basis of colocalization of subunits within individual neurons, as analyzed by confocal laser microscopy in double- and triple-immunofluorescence staining experiments. The results reveal an extraordinary heterogeneity in the distribution of GABAA-receptor subunits, as evidenced by abrupt changes in immunoreactivity along well-defined cytoarchitectonic boundaries and by pronounced differences in the cellular distribution of subunits among various types of neurons. Thus, functionally and morphologically diverse neurons were characterized by a distinct GABAA-receptor subunit repertoire. The multiple staining experiments identified 12 subunit combinations in defined neurons. The most prevalent combination was the triplet alpha 1/beta 2,3/gamma 2, detected in numerous cell types throughout the brain. An additional subunit (alpha 2, alpha 3, or delta) sometimes was associated with this triplet, pointing to the existence of receptors containing four subunits. The triplets alpha 2/beta 2,3/gamma 2, alpha 3/beta 2,3/gamma 2, and alpha 5/beta 2,3/gamma 2 were also identified in discrete cell populations. The prevalence of these seven combinations suggest that they represent major GABAA-receptor subtypes. Five combinations also apparently lacked the beta 2,3-subunits, including one devoid of gamma 2-subunit (alpha 1/alpha 2/gamma 2, alpha 2/gamma 2, alpha 3/gamma 2, alpha 2/alpha 3/gamma 2, alpha 2/alpha 5/delta).(ABSTRACT TRUNCATED AT 400 WORDS)

Neurons projecting from the entopeduncular nucleus to the thalamus receive convergent synaptic inputs from the subthalamic nucleus and the neostriatum in the rat.

The two major afferents of the entopeduncular nucleus are the subthalamic nucleus and the neostriatum, which have opposing physiological effects on entopeduncular neurons. Experiments were performed to test the hypothesis that individual entopeduncular neurons that project to the thalamus receive convergent synaptic input from both the subthalamic nucleus and the neostriatum in the rat. This was achieved using double anterograde tracing combined with retrograde tracing. In the electron microscope anterogradely labelled subthalamic (Subthalamic Type 1) and neostriatal terminals were observed to form asymmetrical and symmetrical synaptic contacts respectively, with all parts of entopeduncular neurons. Labelled subthalamic and neostriatal terminals were observed in convergent synaptic contact with entopeduncular neurons, some of which were retrogradely labelled from the thalamus. A second rarer type of terminal was labelled (Subthalamic Type 2) which formed symmetrical synaptic contacts with the proximal regions of unlabelled and retrogradely labelled entopeduncular neurons. These terminals are believed to be derived from the globus pallidus. It is concluded that the topographical and synaptic organization of the so-called direct (neostriatum to entopeduncular nucleus) and indirect pathways (involving the subthalamus and the globus pallidus) is capable of mediating the inhibition and excitation of output neurons in the entopeduncular nucleus that occur following neostriatal stimulation.

GABAergic terminals in nucleus magnocellularis and laminaris originate from the superior olivary nucleus.

The auditory brainstem nuclei, angularis (NA), magnocellularis (NM), and laminaris (NL) of the chicken, Gallus, contain terminals that stain for antibodies against the inhibitory neurotransmitter, gamma-aminobutyric acid (GABA). Some of these terminals originate from cells surrounding nucleus magnocellularis. Results from this study indicate that the majority of the GABAergic terminals found in NA, NM and NL originate from the superior olivary nucleus (SON). Injections of cholera toxin and horseradish peroxidase show that superior olivary nucleus (SON) neurons, which respond to pure tones, project bilaterally to NA, NM, and NL. NA and NL are reciprocally connected with the SON. More NA cells project to the SON than NL cells. While SON neurons project to NM, NM neurons do not project axons back to the SON. The configuration of SON terminals in NA, NM and NL matches the pattern of GABA-immunoreactive puncta seen in these three nuclei: they surround individual NM cells, congregate in the dendritic neuropil of NL, and blanket the NA. The data indicate that NA, NM and NL may be affected by two different inhibitory cell types: local interneurons and SON neurons. Patterns of connectivity described in this report suggest that the activity of NA cells could influence NM and NL cell physiology. Specifically, increases in NA cell activity could augment the effects of GABAergic SON neurons on NM and NL. Hence, binaural perception in the chicken may be more dependent upon changes in intensity cues than previously believed.

Germ cell tumors of the basal ganglia and thalamus.

The clinicopathological findings in 6 patients with germ cell tumors originating in the basal ganglia and thalamus are presented. Clinical, biological and diagnostic features were somewhat different from germ cell tumors in the pineal region. Early and comprehensive treatment is recommended because of the possible presence of nongerminomatous germ cell components.

Fine structure of zonal changes in experimental Nd:YAG laser-induced interstitial hyperthermia.

Interstitial thermotherapy using Nd:YAG-laser induced hyperthermia is a new stereotactic method for the treatment of brain tumors in poorly accessible regions. To provide a basis for the underlying tissue alterations, we have analyzed the spatial and temporal pattern of interstitial laser hyperthermia lesions in the normal rat brain by histological, immunohistochemical, and electron microscopical methods. The acute changes corresponded to the temperature gradient surrounding the laser probe and showed a distinct zonal architecture. Membrane destruction on a cellular and subcellular level appears to be of major significance in the pathogenesis of the laser lesion. The tissue reaction followed the course known for coagulation necrosis and resulted in a well-defined defect. These results, although limited by the choice of the experimental model, may be helpful in the interpretation of images obtained in future applications of interstitial thermotherapy.

Tachykinin systems in the spinal cord and basal ganglia: influence of neonatal capsaicin treatment or dopaminergic intervention on levels of peptides, substance P-encoding mRNAs, and substance P receptor mRNA.

The aim of the study was to test whether the synthesis of substance P (SP) and that of its receptor (also known as NK1 receptor) are coordinately regulated after chronic pharmacologic intervention in two neural systems, the spinal cord and basal ganglia. In one set of experiments, capsaicin was administered subcutaneously during the early postnatal period (day 3 after birth) to induce degeneration of afferent sensory neurons in the spinal cord. In the other set of experiments, interruption of dopaminergic transmission was achieved by two methods: (a) The neurotoxin 6-hydroxydopamine was used to denervate dopaminergic neurons during the early postnatal period, and (b) haloperidol was used in adult animals to block dopaminergic transmission by receptor blockade. The spinal cord, striatum, or both were used for the quantification of tachykinin [SP and neurokinin A (NKA)] and opioid peptides [[Met5]-enkephalin (ME) and dynorphin A (1-8) (DYN)] by radioimmunoassays. The abundance of total SP-encoding preprotachykinin (PPT) mRNA and SP receptor (SPR) mRNA in spinal cord (C5 to T1 segments), striatum, or microdissected substantia nigra was determined by northern blot or solution hybridization analysis. Amines and their acid metabolites were quantified by HPLC. Capsaicin administration (subcutaneously) during the early postnatal period increased latency in a hot-plate test, decreased SP and NKA levels, increased levels of PPT mRNAs, and did not affect SPR mRNA levels in the spinal cord. Intraspinal SP systems may attempt to compensate for the loss of afferent SP input, whereas spinal cord receptor mRNA levels do not appear to be altered.(ABSTRACT TRUNCATED AT 250 WORDS)

Claustrum in the hedgehog (Erinaceus europaeus) brain: cytoarchitecture and connections with cortical and subcortical structures.

The cytoarchitecture of the claustrum in the hedgehog (Erinaceus europaeus) brain, the morphology of its neurons, and the efferent connections with cortical and subcortical structures were studied with the Nissl and Klüver-Barrera, the Golgi, and the horseradish peroxidase methods. It was found that the claustrum is a well developed nucleus in the hedgehog telencephalon and, as in other mammals, is divided into dorsal and ventral parts. In Golgi-stained sections, spiny multipolar cells are the predominant neurons of both the dorsal and the ventral claustrum and are projection neurons. Aspiny multipolar neurons with fewer, often beaded, dendrites constitute a minority in both divisions and are interneurons. Injections of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) in the prefrontal, motor, somatosensory, auditory and visual areas, and HRP or WGA-HRP injections in the thalamus showed that: (1) the claustroneocortical projections originate in the dorsal claustrum and are distributed to the entire neocortex; these projections are mainly ipsilateral but some also originate contralaterally; (2) the claustroneocortical projections show a rough topographic organization; there exists a substantial degree of overlap; and (3) the claustrothalamic projection, arising throughout the dorsal claustrum, is strictly ipsilateral. No evidence of a thalamoclaustral projection was found. The present results suggest that, although the hedgehog has been referred to as a "paleocortical mammal" owing to the great development of its rhinencephalic structures in comparison with its small neocortex, the dorsal claustrum is well developed and is connected with all neocortical areas as well as with the thalamus, establishing it as a key structure in the hedgehog forebrain.

Fine needle aspiration biopsy of deep cerebrum. A comparison of normal and neoplastic morphology.

Fine needle aspirates of deep white matter, basal ganglia and thalamus from necropsies of three neurologically normal men were compared with two aspirates of cerebral infarcts and with eight aspirates from neoplasms that occurred in the deep cerebrum. Normal white matter contained oligodendroglia with small, dark, round nuclei and astrocytes with larger, bland, oval nuclei and occasional cytoplasmic extensions. Basal ganglia and thalamus contained, in addition, numerous neurons with large nuclei and prominent nucleoli. Recognition of these normal components of the deep cerebral structures is necessary to avoid erroneous diagnoses of neoplasia.

Calcification of basal ganglia and cerebellar roof nuclei in mentally defective patient with hidrotic ectodermal dysplasia. Analysis of intracranial concretions by electon microprobe.

This report describes, for the first time, an analysis by electron microprobe of concretions in the brain of an individual with striopallidodentate calcification. We also report the unique association of this intracranial syndrome with hidrotic ectodermal dysplasia. An institutionalized male with impaired intellectual function and hidrotic ectodermal dysplasia was known since the age of 3 years to have bilateral radiopaque densities in the region of the basal ganglia on skull roentgenogram. He died at age 29 in congestive heart failure from rheumatic pancarditis. At autopsy, concretions were identified in globus pallidus, caudate nuclei, thalamus, and dentate nuclei. Mineral deposits within the brain, analyzed by energy dispersive x-ray microanalysis, consisted predominately of calcium and phosphorus. Trace amounts of magnesium, iron, and silicon also were detected.

Brain involvement in Whipple's disease: a case report.

A man of 22 with Whipple's disease suffered from a acute febrile state and unconsciousness. Focal inflammatory lesions accompanied by large numbers of peculiar macrophages occurred in thalamus and basal ganglia. The electron microscopic findings conform to previous reports on brain involvement in Whipple's disease.