INVOLVEMENT OF HIPPOCAMPAL AMPA GLUTAMATE-RECEPTOR CHANGES AND THE CAMP PROTEIN KINASE A/CREB-P SIGNALING PATHWAY IN MEMORY CONSOLIDATION OF AN AVOIDANCE TASK IN RATS/

Training in step-down inhibitory avoidance (0.3-mA footshock) is follo wed by biochemical changes in rat hippocampus that strongly suggest an involvement of quantitative changes in glutamate AMPA receptors, foll owed by changes in the dopamine D-1 receptor/cAMP/protein kinase A (PK A)/CREB-P signalling pathway in memory consolidation. AMPA binding to its receptor and levels of the AMPA receptor-specific subunit GluR1 in crease in the hippocampus within the first 3 h after training (20-70%) . Binding of the specific D-1 receptor ligand, SCH23390, and cAMP leve ls increase within 3 or 6 h after training (30-100%). PKA activity and CREB-P levels show two peaks: a 35-40% increase 0 h after training, a nd a second increase 3-6 h later (35-60%). The results correlate with pharmacological findings showing an early post-training involvement of AMPA receptors, and a late involvement of the D-1/cAMP/PKA/CREB-P pat hway in memory consolidation of this task.