ENVIRONMENTAL STIMULATION PROMOTES CHANGES IN THE DISTRIBUTION OF PHORBOL ESTER RECEPTORS

The translocation of protein kinase C (PKC) from the cytosol to the me mbrane might be functionally involved in learning and memory. Using [H -3]-phorbol 12,13-dibutyrate (H-3-PDBu) binding three pools of binding sites could be distinguished in tissue preparations: Pool a comprised the soluble receptors which bound phorbol ester with low affinity in the absence of calcium. Pool b was composed of high-affinity phorbol e ster binding sites identified in the soluble fraction upon addition of calcium. Pool c represented stably membrane-bound receptors binding p horbol ester independently of calcium. H-3-PDBu binding was then measu red in the cortices and hippocampi of rats trained in an eight-arm rad ial maze. A progressive training-dependent increase of membrane-bound binding activity with a concomitant decrease in the soluble fraction w as detected independent of learning the maze task. These results sugge st that it is the experience of an enriched environment by the repeate d behavioral stimulation in a maze rather than the acquisition of a me mory task that leads to enhanced incorporation of phorbol ester recept ors (PKC) into the cell membrane.