Aging related changes in the expression of CREB1, CREB2 and S6K in identified single neurons of the abdominal ganglia. Single neuron qPCR analysis of expression of CREB1, CREB2 and S6K mRNAs in old neurons when compared to that of mature neurons are shown in bar graphs. (A) Identified neurons in the abdominal ganglia of Aplysia. Single neurons analyzed in this study are color labeled; (B) In the case of old R15, all three genes are significantly downregulated; (C) In old R2, CREB1 and S6K are significantly upregulated. CREB2 did not change with aging in R2; (D) In old L11, CREB1 and CREB2 do not show any significant down regulation, whereas S6K is downregulated significantly; (E) In old L7, all the three genes are downregulated significantly. Figures 5F-H represent the percent change in gene expression of individual genes in different identified neurons of abdominal ganglia during aging. (F) Significant changes in expression of CREB1 in R15 (90 ± 5%), R2 (80 ± 5%) and L7 (50 ± 5%). The change in L11 was not significant; (G) CREB2 showed significant changes in expression levels in R15 (70 ± 5%) and L7 (70 ± 5%) and but no significant changes in R2 and L11; (H) S6K expression changes significantly in all four neurons, R15 (30 ± 5%), L11 (50 ± 5%), L11 (70 ± 5%), and R2 (400 ± 15%). Ct values of target genes were normalized to 18S rRNA internal standard. Each measurement consists of 5 biological repeats, 4 technical repeats and the error bars indicate standard error of the mean (SEM). Student’s t test determined statistical significance where **P-value < 0.01, ***P-value < 0.001.