Effect of age and SKF 83959 on expression of TrkBfull and TrkB.T1 in NAc, CP and PFC of adult and juvenile rats. (a) Representative blots depicting age-related and SKF 83959-induced changes in full length (TrkBfull) and truncated TrkB (TrkB.T1) are shown. GAPDH was used as a loading control. (b) Adult and juvenile rats exhibited similar basal expression levels of the active isoform TrkBfull in all three regions examined. SKF 83959 (1.5 mg/kg s.c.) did not alter TrkBfull expression in NAc, CP or PFC {NAc: Drug, F(1,21)=4.4, P=0.049; Age, F(1,21)=0.4, P=0.54, n.s.; Drug × Age, F(1,21)=0.3, P=0.59, n.s.; CP: Drug, F(1,21)=6.7, P=0.017; Age, F(1,21)=4.7, P=0.042; Drug × Age, F(1,21)=0.9, P=0.35, n.s.; PFC: Drug, F(1,22)=2.2, P=0.15, n.s.; Age, F(1,22)=13.2, P=0.001; Drug × Age, F(1,22)=1.2, P=0.29, n.s.}. (c) Juvenile animals showed lower basal levels of TrkB.T1 expression compared to adults in NAc and CP, with no differences in PFC. SKF 83959 did not alter TrkB.T1 expression in any region in adult rats, but elevated the expression of this TrkB isoform in NAc and CP, but not PFC, of juvenile rats {NAc: Drug, F(1,21)=3.0, P=0.10; Age, F(1,21)=2.6, P=0.12; Drug × Age, F(1,21)=4.2, P=0.048; CP: Drug, F(1,21)=24.1, P=0.0001; Age, F(1,21)=2.8, P=0.11, n.s.; Drug × Age, F(1,21)=4.6, P=0.044; PFC: Drug, F(1,21)=2.7, P=0.11, n.s.; Age, F(1,21)=1.4, P=0.25, n.s.; Drug × Age, F(1,21)=2.7, P=0.11, n.s.}. (d) The ratio of expression of full to truncated TrkB isoforms. Juvenile rats showed a significantly higher basal TrkB ratio (TrkBfull:TrkB.T1) compared to adults in NAc, CP and PFC. SKF 83959 increased the TrkB ratio in adult rats in NAc and PFC, with no effects in these regions in juvenile rats. In CP, SKF 83959 significantly reduced the TrkB ratio in juvenile rats with no effect in adults. Data are represented as mean ± SEM, and are expressed as a percent of adult/saline controls. {NAc: Drug, F(1,20)=0.01, P=0.92, n.s.; Age, F(1,20)=16.1, P=0.001; Drug × Age, F(1,20)=9.5, P=0.006; CP: Drug, F(1,21)=27.8, P=0.0001; Age, F(1,21)=51.2, P=0.0001; Drug × Age, F(1,21)=26.9, P=0.0001; PFC: Drug, F(1,22)=0.1, P=0.71, n.s.; Age, F(1,22)=22.5, P=0.0001; Drug × Age, F(1,22)=0.002, P=0.97, n.s.}. N=6-7/group per experiment. **P<0.01, ***P<0.001 compared to basal expression of adults rats; #P<0.05, ###P<0.001 compared to saline controls of the same age.