Figure 2
β-adrenergic receptor enables TPS and HFS-induced LTP in the ventral hippocampus. (A) A brief train of TPS (5 s) had no lasting effect on synaptic strength in control experiments (fEPSPs were 101 ± 2% of baseline 45 min post-TPS, n = 10) but induced LTP when delivered in the presence 1.0 µM ISO (fEPSPs potentiated to 149 ± 7% of baseline, n = 14, t(20) = 5.881, **p = 6.43 × 10–6, compared to control). (B) β-adrenergic receptor activation enables the induction of LTP by a longer train of TPS (3 min). fEPSPs were 101 ± 4% of baseline in control experiments (n = 11) and 155 ± 7% of baseline in experiments were TPS was delivered in the presence of ISO (n = 14, t(23) = 6.502, **p = 1.24 × 10–6, compared to control). (C) In ventral hippocampal slices fEPSPs were potentiated to 141 ± 5% of baseline in control experiments (n = 9) and 216 ± 8% of baseline when HFS was delivered in the presence of ISO (n = 9). (D) In dorsal hippocampal slices fEPSPs were 182 ± 8% of baseline 60 min post-HFS in control experiments (n = 7) and 191 ± 8% of baseline when HFS was delivered in the presence of ISO (n = 8). Scatter plots show fEPSP slopes 45 min post-TPS (A and B) or 60 min post-HFS (C and D) in all experiments. For results shown in (C) and (D), statistical significance was determined using a two-way ANOVA and post hoc Bonferroni t-tests. There was a significant effect of region (F(1,29) = 32.764, p < 0.001) and a significant region × ISO interaction (F(1,29) = 20.052, p < 0.001). Although ISO did not enhance LTP in dorsal hippocampal slices (NS, p = 0.406), ISO enhanced LTP induction in slices from the ventral hippocampus (**p < 0.001). In control experiments, HFS-induced LTP was significantly smaller in ventral compared to dorsal hippocampal slices (p < 0.001). Traces in (A–D) show superimposed fEPSPs recorded during baseline and 45 min post-TPS (A, B) or 60 min post-HFS (C, D).
