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1.
Neuroscience ; 153(1): 196-213, 2008 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-18358616

RESUMO

The ventral tegmental area (VTA) is a nodal link in reward circuitry. Based on its striatal output, it has been subdivided in a caudomedial part which targets the ventromedial striatum, and a lateral part which targets the ventrolateral striatum [Ikemoto S (2007) Dopamine reward circuitry: two projection systems from the ventral midbrain to the nucleus accumbens-olfactory tubercle complex. Brain Res Rev 56:27-78]. Whether these two VTA parts are interconnected and to what extent the VTA innervates the substantia nigra compacta (SNc) and retrorubral nucleus (RR) are critical issues for understanding information processing in the basal ganglia. Here, VTA projections to the VTA-nigral complex were examined in rats, using Phaseolus vulgaris leucoagglutinin (PHA-L) as anterograde tracer. The results show that the dorsolateral VTA projects to itself, as well as to the dorsal tier of the SNc and RR, largely avoiding the caudomedial VTA. The ventrolateral VTA innervates mainly the interfascicular nucleus. The components of the caudomedial VTA (the interfascicular, paranigral and caudal linear nuclei) are connected with each other. In addition, the caudomedial VTA (especially the paranigral and caudal linear nuclei) innervates the lateral VTA, and, to a lesser degree, the SNc and RR. The caudal pole of the VTA sends robust, bilateral projections to virtually all the VTA-nigral complex, which terminate in the dorsal and ventral tiers. Modest inputs from the medial supramammillary nucleus to ventromedial parts of the VTA-nigral complex were also identified. In double-immunostained sections, PHA-L-labeled varicosities were sometimes found apposed to tyrosine hydroxylase-positive neurons in the ventral mesencephalon. Overall, the results underscore that VTA projections to the VTA-nigral complex are substantial and topically organized. In general, these projections, like the spiralated striato-nigro-striatal loops, display a medial-to-lateral organization. This anatomical arrangement conceivably permits the ventromedial striatum to influence the activity of the lateral striatum. The caudal pole of the VTA appears to be a critical site for a global recruitment of the mesotelencephalic system.


Assuntos
Substância Negra/anatomia & histologia , Área Tegmentar Ventral/anatomia & histologia , Animais , Transporte Axonal/fisiologia , Mapeamento Encefálico , Dopamina/metabolismo , Feminino , Imuno-Histoquímica , Vias Neurais/anatomia & histologia , Vias Neurais/metabolismo , Neurônios/citologia , Neurônios/metabolismo , Fito-Hemaglutininas , Terminações Pré-Sinápticas/metabolismo , Ratos , Ratos Wistar , Coloração e Rotulagem , Substância Negra/metabolismo , Tegmento Mesencefálico/anatomia & histologia , Tegmento Mesencefálico/metabolismo , Tirosina 3-Mono-Oxigenase/metabolismo , Área Tegmentar Ventral/metabolismo
2.
Neuroscience ; 145(3): 1059-76, 2007 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-17270353

RESUMO

The ventral tegmental area (VTA) is crucially involved in brain reward, motivated behaviors, and drug addiction. This district is functionally heterogeneous, and studying the connections of its different parts may contribute to clarify the structural basis of intra-VTA functional specializations. Here, the efferents of the rostral linear nucleus (RLi), a midline VTA component, were traced in rats with the Phaseolus vulgaris leucoagglutinin (PHA-L) technique. The results show that the RLi heavily innervates the olfactory tubercle (mainly the polymorph layer) and the ventrolateral part of the ventral pallidum, but largely avoids the accumbens. The RLi also sends substantial projections to the magnocellular preoptic nucleus, lateral hypothalamus, central division of the mediodorsal thalamic nucleus, lateral part of the lateral habenula and supraoculomotor region, and light projections to the prefrontal cortex, basolateral amygdala, and dorsal raphe nucleus. A similar set of projections was observed after injections in rostromedial VTA districts adjacent to RLi, but these districts also send major outputs to the lateral ventral striatum. Overall, the data suggest that the RLi is a distinct VTA component in that it projects primarily to pallidal regions of the olfactory tubercle and to their diencephalic targets, the central division of the mediodorsal thalamic nucleus and the lateral part of the lateral habenula. Because the rat RLi reportedly contains a lower density of dopaminergic neurons as compared with most of the VTA, its unusual projections may reflect a non-dopaminergic, putative GABAergic, phenotype, and this distinctive cell population seemingly extends beyond RLi boundaries into the laterally adjacent VTA. By being connected to the central division of the mediodorsal thalamic nucleus (directly and via ventral striatopallidal system) and to the magnocellular preoptic nucleus, the RLi and its surroundings may play a role in olfactory-guided behaviors, which are part of the approach responses associated with appetitive motivational states.


Assuntos
Vias Eferentes/fisiologia , Área Tegmentar Ventral/fisiologia , Animais , Vias Eferentes/anatomia & histologia , Feminino , Fito-Hemaglutininas , Prosencéfalo/anatomia & histologia , Prosencéfalo/fisiologia , Ratos , Ratos Wistar , Área Tegmentar Ventral/anatomia & histologia
3.
Braz. j. med. biol. res ; 37(8): 1161-1174, Aug. 2004. graf
Artigo em Inglês | LILACS | ID: lil-362560

RESUMO

An auditory stimulus speeds up a digital response to a subsequent visual stimulus. This facilitatory effect has been related to the expectancy and the immediate arousal that would be caused by the accessory stimulus. The present study examined the relative contribution of these two influences. In a first and a third experiment a simple reaction time task was used. In a second and fourth experiment a go/no-go reaction time task was used. In each of these experiments, the accessory stimulus preceded the target stimulus by 200 ms for one group of male and female volunteers (G Fix). For another group of similar volunteers (G Var) the accessory stimulus preceded the target stimulus by 200 ms in 25 percent of the trials, by 1000 ms in 25 percent of the trials and was not followed by the target stimulus in 50 percent of the trials (Experiments 1a and 1b) or preceded the target stimulus by 200 ms in 6 percent of the trials and by 1000 ms in 94 percent of the trials (Experiments 2a and 2b). There was a facilitatory effect of the accessory stimulus for G Fix in the four experiments. There was also a facilitatory effect of the accessory stimulus at the 200-ms stimulus onset asynchrony for G Var in Experiments 1a and 1b but not in Experiments 2a and 2b. The facilitatory effects observed were larger in the go/no-go task than in the simple task. Taken together, these results suggest that expectancy is much more important than immediate arousal for the improvement of performance caused by an accessory stimulus.


Assuntos
Humanos , Masculino , Feminino , Adolescente , Adulto , Estimulação Acústica , Nível de Alerta , Atenção , Percepção Auditiva , Tempo de Reação , Análise de Variância
4.
Braz J Med Biol Res ; 37(8): 1161-74, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-15273817

RESUMO

An auditory stimulus speeds up a digital response to a subsequent visual stimulus. This facilitatory effect has been related to the expectancy and the immediate arousal that would be caused by the accessory stimulus. The present study examined the relative contribution of these two influences. In a first and a third experiment a simple reaction time task was used. In a second and fourth experiment a go/no-go reaction time task was used. In each of these experiments, the accessory stimulus preceded the target stimulus by 200 ms for one group of male and female volunteers (GFix). For another group of similar volunteers (GVar) the accessory stimulus preceded the target stimulus by 200 ms in 25% of the trials, by 1000 ms in 25% of the trials and was not followed by the target stimulus in 50% of the trials (Experiments 1a and 1b) or preceded the target stimulus by 200 ms in 6% of the trials and by 1000 ms in 94% of the trials (Experiments 2a and 2b). There was a facilitatory effect of the accessory stimulus for GFix in the four experiments. There was also a facilitatory effect of the accessory stimulus at the 200-ms stimulus onset asynchrony for GVar in Experiments 1a and 1b but not in Experiments 2a and 2b. The facilitatory effects observed were larger in the go/no-go task than in the simple task. Taken together, these results suggest that expectancy is much more important than immediate arousal for the improvement of performance caused by an accessory stimulus.


Assuntos
Estimulação Acústica/métodos , Nível de Alerta/fisiologia , Percepção Auditiva/fisiologia , Tempo de Reação/fisiologia , Adolescente , Adulto , Análise de Variância , Atenção/fisiologia , Feminino , Humanos , Masculino
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