SPATIAL AND TEMPORAL CHANGES IN SIGNAL-TRANSDUCTION PATHWAYS DURING LTP

Following LTP induction in freely moving rats, in situ hybridization r evealed discrete changes in the expression of one isoform in each of f our families of serine/threonine kinases constitutively expressed in t he dentate gyrus of the hippocampus. Expression of the alpha isoform o f CaMKII showed a transient increase over the soma and a more persiste nt increase over the dendritic field of dentate granule cells. Of the PKC isoforms, only gamma PKC was up-regulated substantially 2 hr after LTP induction, declining to control levels 48 hr later. An increase i n the expression of mRNA for ERK2 and raf-1 was seen at 24 hr only. Th ese results show that, during the maintenance phase of LTP in the hipp ocampus, there are selective increases in the expression of serine/thr eonine kinases and that these increases have specific and characterist ic temporal and spatial profiles.