Although the inferior colliculus is a structure primarily involved with the processing of acoustic information, it is now widely accepted that it also participates in the integration of sensory, autonomic and behavioral aspects of the defense reaction of animals in dangerous situations. Electrical or chemical stimulation of this structure induces defensive responses such as arousal, freezing and escape. It is known that the inferior colliculus has a high concentration of dopaminergic receptors. Dopamine is one of the most active neuromodulator in mechanisms underlying states of fear and anxiety. Furthermore, the inferior colliculus has indirect projections to the amygdala through the medial geniculate nucleus of the thalamus. Recent studies have shown that distinct modulatory mechanisms are recruited in the basolateral amygdala (BLA) during conditioned and unconditioned fear triggered by activation of neural substrates of the inferior colliculus. Thus, the objective of this study is to evaluate whether and how dopaminergic modulation in the inferior colliculus is involved in the expression of unconditioned and conditioned fear responses. For this purpose, male Wistar rats will receive administration of agonists and antagonists of dopaminergic D1 and D2 receptors in the inferior colliculus and will be tested in the elevated plus maze and fear potentiated startle tests.
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