B-50/GAP-43 phosphorylation and PKC activity are increased in rat hippocampal synaptosomal membranes after an inhibitory avoidance training.

CAMMAROTA, M., PARATCHA, G., LEVI DE STEIN, M., BERNABEU, R., IZQUIERDO, I. & MEDINA, J

NEUROCHEMICAL RESEARCH

SPRINGER/PLENUM PUBLISHERS

Lugar: New York; Año: 1997 vol. 22 p. 499 - 505

0364-3190

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-dependentincrease in [3H]phorbol dibutyrate binding to membrane-associated PKC in the hippocampus ofrats subjected to an inhibitory avoidance task. Here we confirm and extend this observation, describingthat a one trial inhibitory avoidance learning was associated with rapid and specific increasesin B-50/GAP-43 phosphorylation in vitro and in PKC activity in hippocampal synaptosomalmembranes. The increased phosphorylation of B-50/GAP-43 was seen at 30 min (+35% relativeto naive or shocked control groups), but not at 10 or 60 min after training. This learning-associatedincrease in the phosphorylation of B-50/GAP-43 is mainly due to an increase in the activity ofPKC. This is based on three different sets of data: 1) PKC activity increased by 24% in hippocampalsynaptosomal membranes of rats sacrificed 30 min after training; 2) B-50/GAP-43 immunoblotsrevealed no changes in the amount of this protein among the different experimentalgroups; 3) phosphorylation assays, performed in the presence of bovine purified PKC or in thepresence of the selective PKC inhibitor CGP 41231, exhibited no differences in B-50/GAP-43phosphorylation between naive and trained animals. In conclusion, these results support the contentionthat hippocampal PKC participates in the early neural events of memory formation of anaversively-motivated learning task.