RESUMO
Survival depends on a balance between seeking rewards and avoiding potential threats, but the neural circuits that regulate this motivational conflict remain largely unknown. Using an approach-food vs. avoid-predator threat conflict test in rats, we identified a subpopulation of neurons in the anterior portion of the paraventricular thalamic nucleus (aPVT) which express corticotrophin-releasing factor (CRF) and are preferentially recruited during conflict. Inactivation of aPVTCRF neurons during conflict biases animal's response toward food, whereas activation of these cells recapitulates the food-seeking suppression observed during conflict. aPVTCRF neurons project densely to the nucleus accumbens (NAc), and activity in this pathway reduces food seeking and increases avoidance. In addition, we identified the ventromedial hypothalamus (VMH) as a critical input to aPVTCRF neurons, and demonstrated that VMH-aPVT neurons mediate defensive behaviors exclusively during conflict. Together, our findings describe a hypothalamic-thalamostriatal circuit that suppresses reward-seeking behavior under the competing demands of avoiding threats.
Assuntos
Aprendizagem da Esquiva/fisiologia , Hormônio Liberador da Corticotropina/metabolismo , Hipotálamo/fisiologia , Núcleos da Linha Média do Tálamo/metabolismo , Rede Nervosa/fisiologia , Neurônios/metabolismo , Núcleo Hipotalâmico Ventromedial/fisiologia , Animais , Escala de Avaliação Comportamental , Conflito Psicológico , Feminino , Hipotálamo/metabolismo , Masculino , Núcleos da Linha Média do Tálamo/citologia , Núcleos da Linha Média do Tálamo/efeitos dos fármacos , Núcleos da Linha Média do Tálamo/efeitos da radiação , Neurônios/efeitos dos fármacos , Núcleo Accumbens/metabolismo , Núcleo Accumbens/fisiologia , Núcleo Accumbens/efeitos da radiação , Optogenética , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Recompensa , Núcleo Hipotalâmico Ventromedial/citologiaRESUMO
Research in fear conditioning has provided a comprehensive picture of the neuronal circuit underlying the formation of fear memories. In contrast, our understanding of the retrieval of fear memories is much more limited. This disparity may stem from the fact that fear memories are not rigid, but reorganize over time. To bring some clarity and raise awareness about the time-dependent dynamics of retrieval circuits, we review current evidence on the neuronal circuitry participating in fear memory retrieval at both early and late time points following auditory fear conditioning. We focus on the temporal recruitment of the paraventricular nucleus of the thalamus (PVT) for the retrieval and maintenance of fear memories. Finally, we speculate as to why retrieval circuits change with time, and consider the functional strategy of recruiting structures not previously considered as part of the retrieval circuit.
Assuntos
Medo/fisiologia , Memória de Longo Prazo/fisiologia , Tonsila do Cerebelo/metabolismo , Animais , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Núcleo Central da Amígdala/fisiologia , Condicionamento Clássico/fisiologia , Humanos , Memória/fisiologia , Núcleos da Linha Média do Tálamo/fisiologia , Vias Neurais/fisiologia , Tálamo/fisiologiaRESUMO
The hydroalcoholic extract of Equisetum arvense (HAE) tested at the doses of 200 and 400 mg/kg showed a significant activity on the open-field, enhanced the number of falls in the rota-rod reducing the time of permanence in the bar and increased the sleeping time (46% and 74%) in the barbiturate-induced sleeping time. In the pentylenetetrazole-seizure, it increased the first convulsion latency, diminished the severity of convulsions, reduced the percentage of animals which developed convulsion (50% and 25%) and protected animals from death. On the contrary, in the elevated plus maze, the doses 50, 100 and 150 mg/kg did not affect the evaluated parameters. Thus, HAE presented anticonvulsant and sedative effects. Phytochemical analysis detected the presence of tannins, saponins, sterols and flavonoids.