EFFECTS ON PROTEIN-SYNTHESIS PRODUCED BY PAIRING DEPOLARIZATION WITH SEROTONIN, AN ANALOG OF ASSOCIATIVE LEARNING IN APLYSIA

A form of associative plasticity in Aplysia, activity dependent neurom odulation, involves the convergence of neuronal activity and the effec ts of a modulatory transmitter. To investigate the role of protein syn thesis in associative plasticity, we examined the effects of a biochem ical analogue of activity-dependent neuromodulation on the level of in corporation of labeled amino acid into proteins. To mimic associative training, abdominal ganglia were exposed to paired treatments of a dep olarizing agent, elevated potassium, and a modulatory transmitter, ser otonin. The effects of elevated potassium and serotonin applied alone were also examined. At least two proteins (nos. 9 and 17) were affecte d in a nonadditive way by the paired procedure. Incorporation of label into protein 9 was increased by the paired procedure but was not affe cted by either elevated potassium or serotonin. Incorporation of label into protein 17 was significantly affected by elevated potassium or s erotonin, but the effect of the paired procedure was significantly les s than the summed effects of elevated potassium and serotonin applied alone. These results indicate that changes in protein synthesis may be important in the induction of associative plasticities. Amino acid se quences of two peptides derived from protein 9 were obtained. Then, a partial cDNA clone for protein 9 was obtained by performing PCR with d egenerate primers corresponding to portions of the sequences of the tw o peptides. The sequence of protein 9 is related to sequences previous ly reported for a family of genes comprising the stringent starvation protein of Escherichia coli, auxin-induced proteins of plants, and glu tathione S-transferases of a number of organisms.