Efeitos da novidade na generalização da memória aversiva: uma investigação da participação dos sistemas noradrenérgico e dopaminérgico

Abstract

The generalization of aversive memory can be defined as a phenomenon in which a similar situation (but distinct) to a previous aversive event can trigger a defensive response and is related to several psychological disorders. In this study, we investigate the effects of novelty on the generalization of fear memories and the participation of noradrenergic and dopaminergic systems in this process. In this study, we investigated the effects of novelty on the generalization of fear memories and the participation of noradrenergic and dopaminergic systems in this process. To test the aversive memory and the generalization of aversive memory, we used the "inhibitory avoidance" (IA) memory task. On day 1, adult male Wistar rats were trained in IA. On day 2, the animals were exposed to a modified inhibitory avoidance (MIA) for 3 minutes − 30 minutes before MIA exposition some animals were exposed to novelty (open field) for 5 minutes. To evaluate the involvement of noradrenergic and dopaminergic systems, immediatly before of novelty exposure, some animals received intrahippocampal infusions of timolol (-adrenergic antagonist), SCH23390 (D1/D5 antagonist) or vehicle. On day 3, to evaluate, respectively, the aversive memory and generalization of aversive memory, half of the animals in each group were tested on IA and another half on MIA. In this study, we demonstrated that exposure to novelty avoids the generalization of aversive memory and that this process is dependent on the activation of the -adrenergic and dopaminergic D1/D5 pathways, since the blockade of these pathways in the CA1 region of the hippocampus with the intra-hippocampal infusion of timolol or SCH23390, respectively, immediately before to exposure to novelty inhibits its effect. Moreover, we observed that exposure to novelty raises the hippocampal levels of noradrenaline and dopamine, which suggest that the increase of these neurotransmitters may influence the promotion of long-term memory (LTM), improving memory and attenuating the aversive memory generalization.