title: Intrahippocampal infusion of an inhibitor of protein kinase A separates short- from long-term memory.
abstract: Rats implanted bilaterally with cannulae in the CA1 region of the dorsal hippocampus were trained in one-trial step-down inhibitory (passive) avoidance, and tested for short- and long-term memory of this task at 1.5-3.0 and at 24 h from training, respectively. At various times after training (0, 22, 45, 90, 135 or 175 min) they received a 0.5 microl infusion of the protein kinase A (PKA) inhibitor, KT5720 (0.1 or 0.5 microg), or of its vehicle (20% dimethylsulfoxide in saline). At the higher dose, KT5720 inhibited PKA activity by 90%. KT5720 blocked long-term memory (LTM) when given either 0 or 175 min posttraining, and short-term memory (STM) when given 0, 22, 45 or 90 min post-training. Therefore, PKA plays a different role in the process of formation of the two types of memory. Its role in LTM may be related to the peak of PKA activity, and to the levels of its substrate, nuclear P-CREB, that have been described in a previous paper to occur at 0 and again at 3 h after training. The role of PKA in STM may well involve other substrates of the enzyme. This finding points to a cleavage between the mechanisms of STM and LTM formation.
authors.affiliation: Centro de Memoria, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: M R
authors.initials: MR
authors.lastname: Vianna
authors.forename: L A
authors.initials: LA
authors.lastname: Izquierdo
authors.forename: D M
authors.initials: DM
authors.lastname: Barros
authors.forename: J H
authors.initials: JH
authors.lastname: Medina
authors.forename: I
authors.initials: I
authors.lastname: Izquierdo
mesh_terms: D000648:Amnesia, Retrograde / Q000139:chemically induced / Q000523:psychology; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D001522:Behavior, Animal / Q000187:drug effects; D002227:Carbazoles; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D006624:Hippocampus / Q000502:physiology*; D007211:Indoles / Q000008:administration & dosage / Q000494:pharmacology; D007267:Injections; D008568:Memory / Q000187:drug effects*; D008570:Memory, Short-Term / Q000187:drug effects*; D011758:Pyrroles / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D011758:Pyrroles; C057416:KT 5720; D017868:Cyclic AMP-Dependent Protein Kinases