ASSOCIATIVE LEARNING DOWN-REGULATES PKC-BETA-2-IMMUNOREACTIVITY AND GAMMA-IMMUNOREACTIVITY IN ASTROCYTES

WE showed previously that associative learning induced a twofold incre ase in protein kinase C gamma-immunoreactivity (PKC gamma-ir) in rabbi t CA1 pyramidal neurons, whereas subicular neurons remained unchanged. Here, we investigated the effects of associative learning on PKC-posi tive astrocytes by determining their numerical density in the CA1 regi on and the subiculum of naive, pseudoconditioned and trace eyeblink co nditioned rabbits. Associative learning induced a 70-80% reduction in the number of PKC beta 2- and gamma-positive astrocytes in the CA1 reg ion, but not in the subiculum. No changes were found in the number of PKC alpha- or beta 1-positive astrocytes in either hippocampal subregi on. These results suggest a conditioning-specific downregulation of PK C beta 2 and gamma in a subset of astrocytes in a brain region where a simultaneous alteration in neuronal PKC gamma was evident.