Limiting glutamate transmission in a Vglut2-expressing subpopulation of the subthalamic nucleus is sufficient to cause hyperlocomotion

The subthalamic nucleus (STN) is a key area of the basal ganglia circuitry regulating movement. We identified a subpopulation of neurons within this structure that coexpresses Vglut2 and Pitx2, and by conditional targeting of this subpopulation we reduced Vglut2 expression levels in the STN by 40%, leaving Pitx2 expression intact. This reduction diminished, yet did not eliminate, glutamatergic transmission in the substantia nigra pars reticulata and entopeduncular nucleus, two major targets of the STN. The knock-out mice displayed hyperlocomotion and decreased latency in the initiation of movement while preserving normal gait and balance. Spatial cognition, social function, and level of impulsive choice also remained undisturbed. Furthermore, these mice showed reduced dopamine transporter binding and slower dopamine clearance in vivo, suggesting that Vglut2-expressing cells in the STN regulate dopaminergic transmission. Our results demonstrate that altering the contribution of a limited population within the STN is sufficient to achieve results similar to STN lesions and high-frequency stimulation, but with fewer side effects.

Limiting glutamate transmission in a Vglut2-expressing subpopulation of the subthalamic nucleus is sufficient to cause hyperlocomotion

The subthalamic nucleus (STN) is a key area of the basal ganglia circuitry regulating movement. We identified a subpopulation of neurons within this structure that coexpresses Vglut2 and Pitx2, and by conditional targeting of this subpopulation we reduced Vglut2 expression levels in the STN by 40%, leaving Pitx2 expression intact. This reduction diminished, yet did not eliminate, glutamatergic transmission in the substantia nigra pars reticulata and entopeduncular nucleus, two major targets of the STN. The knock-out mice displayed hyperlocomotion and decreased latency in the initiation of movement while preserving normal gait and balance. Spatial cognition, social function, and level of impulsive choice also remained undisturbed. Furthermore, these mice showed reduced dopamine transporter binding and slower dopamine clearance in vivo, suggesting that Vglut2-expressing cells in the STN regulate dopaminergic transmission. Our results demonstrate that altering the contribution of a limited population within the STN is sufficient to achieve results similar to STN lesions and high-frequency stimulation, but with fewer side effects.

Os núcleos dopaminérgicos do mesencéfalo do mocó (kerodon rupestris): caracterização citoarquitetônica e por imunoistoquímica para tirosina-hidroxilase

The 3-hydroxytyramine/dopamine (DA) is a monoamine of catecholamineric group and consists in the progenitor substantia of synthesis of noradrenaline and adrenaline, having the enzyme tyrosine hydroxylase as a regulator of this process. Nuclei of midbrain expressing DA are the retrorubral field (RRF, A8 group), the substantia nigra pars compacta (SNc, A9 group) and the ventral tegmental area (VTA, A10 group). These nuclei are involved in three complex circuitry called mesostriatal, mesocortical and mesolimbic, which are related directly with various behavioral manifestations such as motor control, reward signaling in behavioural learning, motivation and pathological manifestations of Parkinson s disease and schizophrenia. The aim of this study was describe the morphology of midbrain dopaminergic neurons (A8, A9 and A10) of the rock cavy (Kerodon rupestris), a rodent belonging to the family Caviidae typical of the Brazilian Northeast, which is being adopted as a model for neuroanatomical studies in laboratory of neuroanatomy of the Federal University of Rio Grande do Norte. Coronal sections of brains of the rock cavies were submitted to staining by Nissl s method and immunohistochemistry against tyrosine hydroxylase. The nuclear organization of the midbrain dopaminergic nuclei of the rock cavy is very similar to that found in other animals of the order Rodentia, except by the presence of the tail of substantia nigra, which was found only in the studied species. We concluded that the midbrain dopaminergic nuclei are phylogenetically stable among species, but we think to be it necessary to expand the studies about the particularity found the rock cavy, investigating its occurrence in other species of rodents or investigating its functional relevance

Caracterização citoarquitetônica e por imunoistoquímica para tirosina-hidroxilase da substância negra, área tegmentar ventral e zona retrorubral do Sagui (Callithrix jacchus)

It is known that the catecholamine group is constituted by dopamine, noradrenaline and adrenaline, in which the synthesis is regulated by an enzyme named tyrosine hydroxylase. Thus, 3-hydroxytyramine/dopamine (DA) is a precursor of the noradrenaline and adrenaline synthesis and acts as a neurotransmitter in the central nervous system. The three main nuclei, named the retrorubral field (A8 group), the substantia nigra pars compacta (A9 group) and the ventral tegmental area (A10 group), are arranged in the die-mesencephalic portion and are involved in three complexes circuitries - the mesostriatal, mesolimbic and mesocortical pathways. These pathways are related to behavioral manifestations, motricity, learning, reward and pathologies such as Parkinson’s Disease and Schizophrenia. Thus, the aim of this study was to perform de morphological analysis of the A8, A9 and A10 nuclei of the common marmoset (Callithrix jacchus). The marmoset is a neotropical primate, whose morphological and functional characteristics supports the suitability of use of this animal in biomedical research. Coronal sections of the marmoset brain were submitted to cytoarchitectonic characterization and TH-immunohistochemistry. Based on the morphology of the neurons, it was possible to subdivide the A10 group in seven regions: interfascicular nucleus, raphe rostral linear nucleus and raphe caudal linear nucleus, in the middle line; paranigral and parainterfascicular nucleus, in the middle zone; rostral portion of the ventral tegmental area nucleus and parabrachial pigmented nucleus, located in the dorsolateral portion of the mesencephalic tegmentum. A9 group was divided into four regions: substantia nigra compacta dorsal and ventral tiers; substantia nigra compacta lateral and medial clusters. No subdivisions were founded into A8 group. These results revealed that A8, A9 and A10 are phylogenetically conserved between species, but it’s necessary to expand the studies about this compartmentalization, investigating its occurrence in other primate species or investigating its functional relevance.

Modelo animal da Doença de Parkinson baseado na expressão de alfa - sinucleína: caracterização comportamental, eletrofisiológica e avaliação dos efei tos da estimulação da medula espinhal

Parkinson disease (PD) is associated with motor symptoms and dopaminergic cell loss in the nigrostriatal pathway. Alpha-synuclein is the major component of the Lewy bodies, the biological hallmarks of disease, and has been associated with familial cases of PD. Recently, the spinal cord stimulation (SCS) showed to be effective to alleviate the Parkinson symptoms in animal models and human patients. In this project, we characterized the motor and electrophysiological effects of alpha-synuclein overexpression in the substantia nigra of rats. We further investigated the effects of spinal electrical stimulation, AMPT and L-dopa administration in this model. Method: Sprague-Dawley rats were injected with empty viral vector or the vector carrying the gene for alpha-synuclein in the substantia nigra, and were tested weekly for 10 weeks in the open field and cylinder tests. A separated group of animals implanted with bilateral electrode arrays in the motor cortex and the striatum were recorded in the open field, during the SCS sessions and the pharmacological experiments. Results: Alpha-synuclein expression resulted in motor asymmetry, observed as the reduction in use of contralateral forepaw in the cylinder test. Animals showed an increase of local field potential activity in beta band three and four weeks after the virus injection, that was not evident after the 5th week. AMPT resulted in a sever parkinsonian state, with reduction in the locomotor activity and significant peak of oscillatory activity in cortex and striatum. SCS was effective to alleviate the motor asymmetry at long term, but did not reduce the corticostriatal low frequency oscillations observed 24 hs after the AMPT administration. These oscillations were attenuated by L-dopa that, even as SCS, was not effective to restore the locomotor activity during the severe dopaminergic depletion period. Discussion: The alpha-synuclein model reproduces the motor impairment and the progressive neurodegenerative process of PD. We demonstrated, by the first time, that this model also presents the increase in low frequency oscillatory activity in the corticostriatal circuit, compatible with parkinsonian condition; and that SCS has a therapeutic effect on motor symptom of this model.

Citoarquitetura e imunoistoquímica para tirosinahidroxilase dos núcleos dopaminérgicos mesencefálicos do morcego (Artibeus planirostris)

The 3-Hidroxytyramine/dopamine (DA) is a monoamine of catecholamine family and isthe precursor substance synthesis of noradrenaline and adrenaline, having the enzymeTyrosine Hydroxylase (TH) as this regulatory process. In addition, the DA has theability to act as a neurotransmitter in the Central Nervous System - SNC, being themain neurotransmitter of brain nuclei, namely of A8 to A16. The nuclei of the midbrainthat express DA are the Retrorubral Field (RRF, A8), the Substantia Nigra parsCompacta (SNc, A9) and the Ventral Tegmental Area (VTA, A10). Such nuclei areinvolved in complex three circuitry that are the mesostriatal, mesolimbic andmesocotical and are directly related with several behavioral manifestations as motricitycontrol, reward signaling in behavioral learning, motivation and pathologicalconditions, such as Parkinson's Disease and schizophrenia. Interestingly, many of themorphological bases of these neural disturbance remain unknown. Considering therelevance of mesencephalic dopaminergic nuclei, the aim of this research is tocharacterize morphologically the dopaminergic nuclei (clusters A8, A9 and A10) of themidbrain of the bat (Artibeus planirostris). The Artibeus planirostris is a common bat inRio Grande do Norte. Ten animals were used in this research. The animals wereanesthetized, perfused, and the brain was removed from the skull. After dehydration insucrose, the brain was underwent microtomy. Saggital and coronal sections wereobtained and collected in six separate series. The series were Nissl-stained to identifythe cytoarchitectonic boundaries and the other series were subjected toimmunohistochemistry for TH. After cytoarchitectonic analysis and TH+ cellsidentification was possible to establish the anatomical boundaries of the nuclei, as wellas the subdivisions of three of the midbrain dopaminergic nuclei. The SNc is the mostrostral nucleus observed in the midbrain and is identified throughout the rostrocaudalextension of the midbrain. The VTA neurons were seen immediately caudal to the SNcappearance. The RRF neurons were observed just in the caudal levels of the midbrain.The SNc in Artibeus planirostris shows a particular feature, the tail of the SNc. The tailhave been described just in two other studied species. The present work shows aparticular variation in the organizational morphology of the SNc in the artibeus andcontribute to understand the phylogenetic routes by which the dopaminergic system hasevolved.

Avaliação de efeitos DW extratos de sambucus australis E sambucus nigra na marcação de constituintes sanguineos com tecnécio-99M, na morfologia de Hemácias de ratos wistar, na topologia plasmidial e na ação do cloreto estanoso no DNA Plasmidial

Radiobiocomplexes are used in nuclear medicine to obtain images and to treat diseases. Blood constituents have been used as radiobiocomplexes. Natural or synthetic products can influence on the labeling of blood constituents with technetium-99m (99mTc), the morphology of red blood cells and on the stannous chloride (SnCl2) action on plasmid DNA. Sambucus australis and Sambucus nigra are used in popular culture for treating diseases. The aim of this work was to evaluate the effects of the extracts of Sambucus australis and Sambucus nigra on the labeling of blood constituents with 99mTc, on morphology of red blood cells of Wistar rats, on the topology of plasmids DNA and the action against the SnCl2 effects on the DNA of plasmids pBSK. On the labeling of blood constituents with 99mTc it was verified that both extracts were capable to decrease significantly the radioactivity in the cellular compartment and in the insoluble fraction of plasma. Sambucus australis also decreased the labeling of insoluble fraction of blood cells with 99mTc. Both extracts did not alter the morphology of red blood cells. Moreover, it was verified that Sambucus nigra did not alter the electrophoretic profile of plasmid DNA, but decreased the effect of SnCl2 on plasmid DNA. These last results sugest a genotoxic effect and a protective action of Sambucus nigra extract against the SnCl2 action on plasmid DNA. This work was developed with the contribution of several Departments of biomedical area of the Hospital Universitário Pedro Ernesto, of the UERJ, characterizing a multidisciplinary experimental research