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Abstract

The neuropeptide corticotropin-releasing factor (CRF) coordinates the endocrine responses to stress as a major physiological regulator of the hypothalamic-pituitary-adrenal axis. We assessed the effect of the non-peptidergic CRF receptor 1 antagonist CP-154,526 on stress-induced changes in context-dependent fear conditioning and hippocampal synaptic plasticity. The learning impairment of mice trained immediately after I It immobilization could be overcome by preinjection of CP-154,526 before exposure to immobilization. Exposure to acute stress reduced the amount of autophosphorylated Ca2+/calmodulin-dependent protein kinase II (CaNIKII) in the hippocampal CA1 area. When animals were pretreated with CP- 154,526 before immobilization, the amount of hippocampal autophosphorylated CaNIKII was elevated. Electrophysiological studies in the hippocampal CA1 region of stressed animals revealed no significant effects of the CP-154,526 pretreatment on long-term potentiation but a significant elevation of paired-pulse facilitation (PPF) was observed. The CP-154,526- induced enhancements in fear conditioning and PPF could be prevented by the selective CaNIKII inhibitor KN-62. Our results demonstrated that learning impairment after acute stress was antagonized by CP-154,526 pretreatment. (C) 2002 Elsevier Science B.V. All rights reserved.