Corticotropin releasing factor (CRF) plays a crucial role for the modulation of physiological and behavioral responses related to stress. The medial amygdala (MeA) is a critical structure involved with stress/anxiety-related responses and possesses both type 1 and 2 CRF receptors. Previously, we investigated the role played by MeA CRF type 1 receptors in the modulation of two defensive responses measured by the elevated T-maze model of anxiety, avoidance and escape. In clinical terms these responses have been respectively related to generalized anxiety and panic disorder. Our results showed that type 1 receptors selectively modulate avoidance responses, what is important for a better understanding of the physiopathology of generalized anxiety. The present project will further explore the role played by CRF receptors of the MeA, now investigating the effects of the activation and blockage of CRF type 2 receptors. Male Wistar rats will be stereotaxically implanted with two guide cannulae and subsequently administrated with the CRF type 2 agonist urocortine 2 (0,5 e 1,0 ug/0,2 ul), with the CRF type 2 antagonist astressin 2-B (10,7 ug/0,2 ul), with the CRF type 2 antagonist antisauvagine-30 (440 ng/0,2 ul) or with vehicle solution (0,2 ul). Ten minutes after drugs microinjection, the animals will be tested in the elevated-T maze. All animals will also be tested in a open field, after the elevated-T maze, for locomotor activity evaluation.
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