Learning-specific, time-dependent increases in hippocampal Ca2+/calmodulin-dependent protein kinase II activity and AMPA GluR1 subunit immunoreactivity.

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

EUROPEAN JOURNAL OF NEUROSCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Año: 1998 vol. 10 p. 2669 - 2676

0953-816X

Ca2+/calmodulindependent protein kinase II (CAMK II) and one of its target, amino3hydroxy5methylisoxazole4propionic acid (AMPA), glutamate receptors have been shown to participate in both longterm potentiation (LTP) in the hippocampus, and in spatial, as well as in a variety, of learning paradigms. Recently, we were able to demonstrate that the intrahippocampal infusion of a specific inhibitor of CAMK II (KN62) provoked full retrograde amnesia of an inhibitory avoidance learning in rats when given immediately, but not 120 or 240 min, after training. Furthermore, this task is accompanied by a rapid, selective and reversible increase in hippocampal [3H] AMPA receptor binding. Here we report the effect of this aversively motivated learning task on CAMK II activity, and AMPA GluR1 subunit phosphorylation and immunoreactivity in the hippocampus. One trial inhibitory avoidance training is associated with a learningspecific, timedependent increase (25-78%) in both total and Ca2+ independent activities of CAMK II in the hippocampus of rats killed immediately (0 min), but not 120 min, after training. In addition, immunoblotting experiments showed an increment in the amount of the subunit of CAMK II at 0, 30 and 120 min after training. An increase in the in vitro phosphorylation of and subunits of CAMK II was also observed in hippocampal synaptosomal membranes (SPM) of trained rats killed immediately and 30 min posttraining. In addition, inhibitory avoidance is accompanied by a 20% increase in GluR1 phosphorylation and a 33% increase in GluR1 immunoreactivity 120 min after training. No significant changes were observed in shocked animals. Phosphorylation of hippocampal SPM from naive control animals in conditions suitable for CAMK II activation resulted in a large increase in the density of [3H] AMPA binding (+ 100%). Taken together, these findings confirm and extend previous data suggesting that CAMK II and AMPA glutamate receptors in the hippocampus participate in the early phase of memory formation of an inhibitory avoidance learning.