A NEW MODEL FOR FEAR LEARNING IN TROUT

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We propose to develop a new model for fear conditioning using rainbow trout. This model combines elements discovered during our recent work on social stress in lizards and rainbow trout with well defined rodent models for spatial learning (Morris water maze) and fear conditioning. Social aggression is the most potent stressor known, which we utilize in the form of a march larger intruder fish as an unconditioned stimulus (US). This social aggression US is paired with an auditory/somatosensory conditioned stimulus (CS) in context of an escape route (hole) available only to the smaller resident test fish (due to size). Fish either learn to escape from social aggression or remain in the tank to be attacked and subordinated. After seven days of CS-US paairing, on the eighth day the CS is presented alone (without the larger fish), and fish respond either by escaping or by a physiologically conditioned response, elevated plasma cortisol. The model is designed to be used for testing spatial learning in a highly fearful situation, and producing fear conditioning using contextually and ecologically relevant stimuli and behavioral responses. We hypothesize that the neuropeptide CRF regulates which stress coping strategies are adopted by trout during learning in a socially aggressive environment. The aims of this proposal are to: 1. Test and refine the experimental parameters of the model 2. Prove that we can obtain repeatable results 3. Begin to distinguish the role of the CRF in stress coping strategies during fear learning 4. Compare expression of CRF and CRF receptor genes in specific brain regions of trout that do and don't learn to escape using brain punch microdissection and real-time PCR