O hipotálamo modula comportamentos relacionados à motivação, recompensa e punição através de projeções para a área tegmental ventral (VTA), o núcleo dorsal da rafe (DR) e o núcleo tegmental rostromedial (RMTg). Nesse estudo, investigamos através de métodos de rastreamento retrógrado as entradas hipotalâmicas da VTA, do DR e do RMTg e, se neurônios hipotalâmicos individuais inervam mais do que uma dessas regiões. Também determinamos uma possível assinatura GABAérgica ou glutamatérgica das aferências hipotalâmicas, através de rastreamento retrógrado combinado com métodos de hibridação in situ. Observamos que VTA, DR e RMTg recebem um padrão bastante semelhante de entradas hipotalâmicas originando de neurônios de projeção glutamatérgicas e GABAérgicas, a maioria deles (> 90%) inervando somente um desses três alvos. Nossos achados indicam que entradas hipotalâmicas são importantes fontes de sinais homeostáticos para a VTA, o DR e o RMTg. Eles exibem um alto grau de heterogeneidade que permite de excitar ou inibir as três estruturas de forma independente ou em conjunto. / The hypothalamus modulates behaviors related to motivation, reward and punishment via projections to the ventral tegmental area (VTA), dorsal raphe nucleus (DR), and rostromedial tegmental nucleus (RMTg). In this study we investigated by retrograde tracing methods hypothalamic inputs to the VTA, DR, and RMTg, and whether individual hypothalamic neurons project to more than one of these structures. We also determined a possible GABAergic or glutamatergic phenotype of hypothalamic afferents, by combining retrograde tracing with in situ hybridization methods. We found that VTA, DR, and RMTg receive a very similar set of hypothalamic afferents originating from glutamatergic and GABAergic hypothalamic projection neurons, the majority of them (> 90%) only innervating one of these structures. Our findings indicate that hypothalamic inputs are important sources of homeostatic signals for the VTA, DR, and RMTg. They exhibit a high degree of heterogeneity which permits to activate or inhibit the three structures either independently or jointly.

O hipotálamo modula comportamentos relacionados à motivação, recompensa e punição através de projeções para a área tegmental ventral (VTA), o núcleo dorsal da rafe (DR) e o núcleo tegmental rostromedial (RMTg). Nesse estudo, investigamos através de métodos de rastreamento retrógrado as entradas hipotalâmicas da VTA, do DR e do RMTg e, se neurônios hipotalâmicos individuais inervam mais do que uma dessas regiões. Também determinamos uma possível assinatura GABAérgica ou glutamatérgica das aferências hipotalâmicas, através de rastreamento retrógrado combinado com métodos de hibridação in situ. Observamos que VTA, DR e RMTg recebem um padrão bastante semelhante de entradas hipotalâmicas originando de neurônios de projeção glutamatérgicas e GABAérgicas, a maioria deles (> 90%) inervando somente um desses três alvos. Nossos achados indicam que entradas hipotalâmicas são importantes fontes de sinais homeostáticos para a VTA, o DR e o RMTg. Eles exibem um alto grau de heterogeneidade que permite de excitar ou inibir as três estruturas de forma independente ou em conjunto. / The hypothalamus modulates behaviors related to motivation, reward and punishment via projections to the ventral tegmental area (VTA), dorsal raphe nucleus (DR), and rostromedial tegmental nucleus (RMTg). In this study we investigated by retrograde tracing methods hypothalamic inputs to the VTA, DR, and RMTg, and whether individual hypothalamic neurons project to more than one of these structures. We also determined a possible GABAergic or glutamatergic phenotype of hypothalamic afferents, by combining retrograde tracing with in situ hybridization methods. We found that VTA, DR, and RMTg receive a very similar set of hypothalamic afferents originating from glutamatergic and GABAergic hypothalamic projection neurons, the majority of them (> 90%) only innervating one of these structures. Our findings indicate that hypothalamic inputs are important sources of homeostatic signals for the VTA, DR, and RMTg. They exhibit a high degree of heterogeneity which permits to activate or inhibit the three structures either independently or jointly.

Imaging techniques have become much more in demand in modern medicine, especially in fields of disease prognosis, diagnosis and therapeutics. This is because a better understanding of different diseases, characteristics of each patient and further optimizing treatment planning, are all enhanced by advanced imaging techniques. Since each imaging modality has its own merits and intrinsic limitations, combining two or more complementary imaging modalities has become an interesting research area. In this study, gadolinium (Gd3+) doped CdTe quantum dots (QDs) were synthesized and used as multimodal imaging probes of two highly complementary imaging modalities: optical imaging and magnetic resonance imaging. The new imaging probes were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis absorbance spectra, fluorescence spectra (FL) and magnetic resonance imaging (MRI). The optical / MRI imaging probes were further functionalized by conjugating with the axonal tracer dextran amine (10 kDa) for non-invasive axonal tracing observations. Biocompatibility and MRI contrast effect of prepared multimodal imaging probes were investigated by in vitro cell experiments and MRI scanner. Ultimately, it is hoped that this imaging probe will help us better understand the regeneration mechanisms in real time without sacrificing animals at intervening time-points.

The underlying goal of neuroscience research is to understand how the nervous system functions to bring about behavior. A detailed map of neural circuits is required for scientists to tackle this question. To this purpose, we developed a synthetic and genetically-encoded system, TRanscellular ACtivation of Transcription (TRACT) to monitor cell-cell contact. Upon ligand-receptor interaction at sites of cell-cell contact, the transmembrane domain of an engineered Notch receptor is cleaved by intramembrane proteolysis and releases a fragment that regulates transcription in the receptor-expressing cell. We demonstrate that in cultured cells, the synthetic receptor can be activated to drive reporter gene expression by co-incubation with ligand-expressing cell or by growth on ligand-coated surfaces. We further show that TRACT can detect interactions between neurons and glia in the Drosophila brain; expressing the ligand in spatially-restricted subsets of neurons leads to transcription of a reporter in the glial cells that interact with those neurons. To optimize TRACT for neural tracing, we attempted to target the synthetic receptor to post-synaptic sites by fusion with the intracellular domain of Drosophila neuroligin2. However, this modification only facilitate the receptor to be localized homogeneously throughout the neurites. The induction data of the modified receptor shows that the new receptor has better sensitivity compared to the original receptor, but the ligand-receptor interaction still happened at non-synaptic sites of membrane contact. To further target the ligand to pre-synaptic sites, we fused the ligand to different pre-synaptic markers. We found the one fused with synaptobrevin is likely located at axon terminals, but only able to trigger moderate induction. Therefore, more examinations are required to further characterize the capability of this ligand. In summary, TRACT is useful for monitoring cell-cell interactions in animals and could also be used to genetically manipulate cells based on contact. Moreover, we believe that proper targeting of the ligand to synaptic sites will improve the specificity of TRACT for synaptic connections in the future.

O núcleo dorsal da rafe (DR) envia densas projeções para o prosencéfalo e está implicado em várias funções complexas. Muitos estudos indicam que a atividade neuronal do DR é controlada por neurônios do córtex pré-frontal (PFC). Devido à escassez de informações detalhadas sobre as conexões entre o PFC e o DR, objetivamos mapear sistematicamente as projeções do PFC para o DR. O traçador neuronal toxina colérica subunidade b (CTb) foi injetado nas diferentes partes do DR. Com técnica imunoistoquímica contra a CTb, células CTb-ir foram encontradas em maior escala no córtex polar frontal e na parede medial do PFC. No PFC lateral, o córtex da insula agranular dorsal, apresentou maior densidade de neurônios CTb-ir. No PFC orbital, o córtex orbital lateral e dorso-lateral eferentam principalmente a parte central do DR. Injeções situadas na parte caudal do DR resultaram em marcação atenuada. Os resultados indicam que o PFC envia robustas projeções para o DR de forma diferenciada. Através dessas projeções o PFC pode exercer um controle \"top down\" sobre os neurônios do DR. / The dorsal raphe nucleus (DR) sends massive projections to the forebrain and is implicated in a variety of complex functions. Several studies indicate that neuronal activity in the DR is controlled by the prefrontal cortex (PFC). Since there is no detailed information about the projections from the PFC to the DR, the goal of the present study was to map these projections systematically. The neuronal tracer cholera toxin, subunit b (CTb) was injected at different levels of the DR. By immunohistochemical methods, CTb-ir cells were found highly enriched in the frontal polar cortex and in the medial wall of the PFC. In the lateral PFC, the dorsal lateral insular cortex presented the highest density of CTb-ir neurons. In the orbital PFC, the lateral and dorso-lateral orbital cortex project principally to the central segment of the DR. Injections in the caudal segment of the DR resulted in reduced CTb staining. Our results indicate that the PFC sends massive topographically organized projections to the DR, which may exert a \"top down\" control over neurons in the DR.

O núcleo dorsal da rafe (DR) envia densas projeções para o prosencéfalo e está implicado em várias funções complexas. Muitos estudos indicam que a atividade neuronal do DR é controlada por neurônios do córtex pré-frontal (PFC). Devido à escassez de informações detalhadas sobre as conexões entre o PFC e o DR, objetivamos mapear sistematicamente as projeções do PFC para o DR. O traçador neuronal toxina colérica subunidade b (CTb) foi injetado nas diferentes partes do DR. Com técnica imunoistoquímica contra a CTb, células CTb-ir foram encontradas em maior escala no córtex polar frontal e na parede medial do PFC. No PFC lateral, o córtex da insula agranular dorsal, apresentou maior densidade de neurônios CTb-ir. No PFC orbital, o córtex orbital lateral e dorso-lateral eferentam principalmente a parte central do DR. Injeções situadas na parte caudal do DR resultaram em marcação atenuada. Os resultados indicam que o PFC envia robustas projeções para o DR de forma diferenciada. Através dessas projeções o PFC pode exercer um controle \"top down\" sobre os neurônios do DR. / The dorsal raphe nucleus (DR) sends massive projections to the forebrain and is implicated in a variety of complex functions. Several studies indicate that neuronal activity in the DR is controlled by the prefrontal cortex (PFC). Since there is no detailed information about the projections from the PFC to the DR, the goal of the present study was to map these projections systematically. The neuronal tracer cholera toxin, subunit b (CTb) was injected at different levels of the DR. By immunohistochemical methods, CTb-ir cells were found highly enriched in the frontal polar cortex and in the medial wall of the PFC. In the lateral PFC, the dorsal lateral insular cortex presented the highest density of CTb-ir neurons. In the orbital PFC, the lateral and dorso-lateral orbital cortex project principally to the central segment of the DR. Injections in the caudal segment of the DR resulted in reduced CTb staining. Our results indicate that the PFC sends massive topographically organized projections to the DR, which may exert a \"top down\" control over neurons in the DR.