title: B-50/GAP-43 phosphorylation and PKC activity are increased in rat hippocampal synaptosomal membranes after an inhibitory avoidance training.
abstract: Several lines of evidence indicate that protein kinase C (PKC) is involved in long-term potentiation (LTP) and in certain forms of learning. Recently, we found a learning-specific, time-dependent increase in [3H]phorbol dibutyrate binding to membrane-associated PKC in the hippocampus of rats subjected to an inhibitory avoidance task. Here we confirm and extend this observation, describing that a one trial inhibitory avoidance learning was associated with rapid and specific increases in B-50/GAP-43 phosphorylation in vitro and in PKC activity in hippocampal synaptosomal membranes. The increased phosphorylation of B-50/GAP-43, was seen at 30 min (+35% relative to naive or shocked control groups), but not at 10 or 60 min after training. This learning-associated increase in the phosphorylation of B-50/GAP-43 is mainly due to an increase in the activity of PKC. This is based on three different sets of data: 1) PKC activity increased by 24% in hippocampal synaptosomal membranes of rats sacrificed 30 min after training; 2) B-50/GAP-43 immunoblots revealed no changes in the amount of this protein among the different experimental groups; 3) phosphorylation assays, performed in the presence of bovine purified PKC or in the presence of the selective PKC inhibitor CGP 41231, exhibited no differences in B-50/GAP-43 phosphorylation between naive and trained animals. In conclusion, these results support the contention that hippocampal PKC participates in the early neural events of memory formation of an aversively-motivated learning task.
authors.affiliation: Instituto de Biología Celular y Neurociencias, Facultad de Medicina, UBA, Buenos Aires, Argentina.
authors.forename: M
authors.initials: M
authors.lastname: Cammarota
authors.forename: G
authors.initials: G
authors.lastname: Paratcha
authors.forename: M
authors.initials: M
authors.lastname: Levi de Stein
authors.forename: R
authors.initials: R
authors.lastname: Bernabeu
authors.forename: I
authors.initials: I
authors.lastname: Izquierdo
authors.forename: J H
authors.initials: JH
authors.lastname: Medina
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000502:physiology; D002417:Cattle; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019922:GAP-43 Protein; D006624:Hippocampus / Q000648:ultrastructure*; D007425:Intracellular Membranes / Q000201:enzymology; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013574:Synaptosomes / Q000201:enzymology*
chemical_list: D004791:Enzyme Inhibitors; D019922:GAP-43 Protein; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D011493:Protein Kinase C