Polyamine quantification (putrescine, spermidine, acetylputrescine, acetylspermidine) of the brain homogenates in response to 4-month incubation of either AAV9 empty capsid (EC) or AAV9 Tau ΔD421 in 15-month-old nTg and SSAT-/- mice (n = 9–11). a Putrescine: Simple main effects analysis showed that SSAT disruption significantly reduced putrescine (F(1, 35) = 332.618, p = .000). Further, within each genotype, pairwise comparison revealed a trend in difference in putrescine between only the nTg AAV9 empty capsid and nTg AAV9 Tau ΔD421 groups (p = .061). No main effect of AAV9 Tau ΔD421 (F(1, 35) = 1.698, p = .201) or interaction of factors (F(1, 35) = 1.960, p = .170) was detected on putrescine. b Acetylputrescine: Simple main effects analysis showed that SSAT disruption significantly reduced acetylputrescine (F(1, 37) = 57.551, p = .000). No main effect of AAV9 Tau ΔD421 (F(1, 37) = .075, p = .785) or interaction of factors (F(1, 37) = .008, p = .928) was detected on acetylputrescine. c Spermidine: Simple main effects analysis showed that SSAT disruption significantly reduced spermidine (F(1, 37) = 4.736, p = .036). No main effect of AAV9 Tau ΔD421 (F(1, 37) = .001, p = .970) or interaction of factors (F(1, 37) = 2.009, p = .165) was detected on spermidine. d Acetylspermidine: Simple main effects of genotype (F(1, 37) = 27.723, p = .000), AAV9 Tau ΔD421 (F(1, 37) = 11.661, p = .002) and interaction of factors (F(1, 37) = 6.539, p = .015) was detected on acetylspermidine. e Spermine: No main effect of genotype (F(1, 35) = 2.012, p = .165), AAV9 Tau ΔD421 (F(1, 35) = .236, p = .630), or interaction of factors (F(1, 35) = .296, p = .590) was detected on Spermine. f Acetylspermine: Simple main effects analysis showed that SSAT disruption significantly increased acetylspermine (F(1, 38) = 9.360, p = .004). No main effect of AAV9 Tau ΔD421 (F(1, 38) = .004, p = .949) or interaction of factors (F(1, 38) = 2.439, p = .127) was detected on acetylspermine. g SSAT mRNA: mRNA expression of SSAT in response to 4-month incubation of either AAV9 empty capsid (EC) or AAV9 Tau ΔD421 in 15-month old nTg and SSAT-/- mice (n = 3–5). Simple main effects showed that SSAT disruption significantly reduced SSAT expression, normalized to GAPDH, (F(1, 12) = 20.660, p = .001. No effect of AAV9 Tau ΔD421 (F(1, 12) = .687, p = .423) or interaction of factors (F(1, 12) = .694, p = .421) was detected on SSAT expression. 2 × 2 Factorial analysis of variance (ANOVA), followed by pairwise comparisons using Fishers PLSD. *p < .05; asterisks indicate the main effect of treatment and main effect of genotype, ampersands indicate the interaction of genotype and treatment, and number signs indicate the pairwise comparison within genotype. Data is represented by means ± S.E.M.