INHIBITION OF MEMORY CONSOLIDATION AFTER ACTIVE-AVOIDANCE CONDITIONING BY ANTISENSE INTERVENTION WITH EPENDYMIN GENE-EXPRESSION

A rapid increase in ependymin mRNA expression demonstrated by semiquan titative in situ hybridization after avoidance conditioning on goldfis h suggested a molecular demand for newly synthesized ependymin transla tion product. To inhibit de novo synthesis of ependymin molecules with out interference with preexisting on es, 18 mer anti-ependymin mRNA-ph osphorothioate oligodeoxynucleotides (S-ODNs) were injected into the p erimeningeal brain fluid before active avoidance training. S-ODN-injec ted animals learned the avoidance response; however, they were amnesic in the test. When injected into overtrained animals, S-ODNs did not i nterfere with retrieval or performance of the avoidance response. Fish treated with randomized S-ODN sequences served as further controls. I ncorporation of S-ODNs was analyzed by injection of fluorescein isothi ocyanate (FITC)-conjugated oligodeoxynucleotide probes. Microscopic ob servation revealed strong FITC-S-ODN fluorescence in reticular-shaped fibroblasts, the only known site of ependymin synthesis. Results demon strate that selective inhibition of ependymin gene expression in vivo can specifically prevent memory formation. We conclude that in particu lar the newly synthesized ependymin molecules are involved in memory c onsolidation, possibly because they have not yet undergone irreversibl e molecular changes, which have been reported of this glycoprotein in a low-calcium microenvironment.