Pituitary-adrenal influences on avoidance behavior of pigs |
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Authors: | P Mormde R Dantzer |
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Institution: | I.N.R.A., Station de Pharmacologie-Toxicologie, 180, Chemin de Tournefeuille, F-31300, Toulouse, France |
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Abstract: | Pigs submitted to extinction of a signaled conditioned avoidance response were injected daily with various doses of dexamethasone (DX) or ACTH. Pigs treated with 0.2 mg/kg of DX showed a higher number of intertrial crosses, but the extinction rate was not modified by either treatment. The effects of ACTH and DX were further studied on the reaction to a Pavlovian conditioned fear signal presented to pigs having learned a continuous avoidance response in a shuttle-box. DX treatment before both the fear conditioning and the test sessions enhanced the reaction to the fear signal at intermediate doses (0.2 mg/kg) but had little effect at lower (0.1 mg/kg) and higher doses (0.5 and 1 mg/kg). ACTH 1–24 treatment induced the same behavioral changes as intermediate doses of DX. A behaviorally active ACTH 4–9 analog, Org 2766, did not modify behavioral reaction to fear signal presentations when administered before fear conditioning and/or test sessions. These results demonstrate that, in pigs, avoidance performance changes under fear signal presentations are modulated by corticosteroids. |
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