Atuação do núcleo incertus na aquisição e extinção de memórias de medo condicionado

• Autor(a) principal: Pereira, Celia Waylan
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: https://ri.ufs.br/handle/riufs/3266
• topic: Núcleo incertus; Reações defensivas; Medo condicionado; Respostas comportamentais; Amígdala; Nucleus incertus; Defensive responses; Fear conditioning; Behavioral responses; Amygdala; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA

The research of neural mechanisms related to training of emotions has increased in recent years. Fear is a behavior originated in response to the dangers encountering by animals, originating in defensive responses displayed when exposed to threatening stimuli. Fear memory helps animals and humans recognize putative sources of danger and adopt the appropriate behavioral response. The primary neural circuits for fear acquisition and extinction involve connections between prefrontal cortex, ventral hippocampus and amygdala, and these áreas are modulated by brainstem networks. The nucleus (n.) incertus in the dorsal pontine tegmentum provides a strong GABAergic projection to these forebrain centers and is strongly activated by neurogenic stressors. In this study in male, adult rats, we injected miniruby anterograde tracer into n. incertus and delineated its projections to the amygdala; and examined the effect of electrolytic lesions of n. incertus on different stages of the fear conditioning-extinction process. N. incertus-derived nerve fibers were observed in anterior medial amygdala, endopiriform nucleus, intra-amygdala bed nucleus of stria terminalis, amygdalohippocampal transition area, and the ventromedial nucleus of the lateral amygdala, with a broad fiber band present between the basolateral amygdala and the olfactory nuclei of amygdala. In a conventional contextual fear conditioning paradigm, we compared freezing behavior in control (naïve) rats (n = 13), with that in rats after sham- or electrolytic lesions of n. incertus (n = 9/group). There were no differences between the three groups in the habituation, acquisition, or context conditioning phases; but n. incertus-lesioned rats displayed a markedly slower (delayed) extinction of conditioned freezing responses than sham/control rats; suggesting n. incertus-related circuits normally promote extinction through inhibitory projections to amygdala and prefrontal cortex. The results helps in understanding the neurobiological mechanisms involved and in development of the future biotechnological techniques to minimize the effects of disorders associated with fear in humans, such as panic, anxiety and posttraumatic stress disorder.