Dopamine and BDNF Modulate LTP in the BLA Figure 2. Calcium influx, activation of D1 receptors, and induction of the cAMP-PKA cascade are all required for the induction and maintenance of LTP in BLA principal neurons. A, B) Inclusion of the calcium chelator, BAPTA (10 mM) in the patch pipette, fully blocked the induction of LTP by either TBS (n = 6) or 5xHFS (n = 5). C, D) Endogenous dopamine was released during TBS and 5xHFS and was necessary for the induction of LTP in BLA principal neurons. Incubation with SCH23390 (10 mM) before and during TBS (n = 6) or 5xHFS (n = 6) completely abolished the induction of LTP. E, F) The induction LTP by either TBS or 5xHFS was dependent on activation of the cAMP-PKA signaling cascade. Intracellular application of PKA inhibitor KT5720 (100 nM) fully blocked TBS-induced LTP (n = 5), as well as 5xHFS-induced LTP (n = 5). doi:10.1371/journal.pone.0026065.g002 re-uptake with GBR12783 for 10 min prior to 5xHFS significantly enhanced the magnitude of LTP in all neurons tested compared to that induced in control ACSF (210610% of baseline, n = 6, 4 animals, P,0.01, Figure 3A, red squares). Application of GBR12783 caused no enduring change in input resistance at any time point (F (10, 88) = 0.68, P = 0.7366, Two-way ANOVA). However, because application of GBR12783 enhanced both PTP (213610% of baseline, 10 min following 5xHFS) and LTP, we next compared the PPR before, and at 10 and 30 min post of 5xHFS (Figure 3C, D). As illustrated in Figure 3D the PPR was not significantly different from control values 10 or 30 min after LTP induction (P ,0.05), suggesting that the facilitation of PTP and LTP induced by GBR12783 was due to a facilitation of the postsynaptic response and not due to recruitment of an additional presynaptic component. To ensure that blockade of dopamine re-uptake was not recruiting additional receptor subtypes; we then tested whether the enhancement of LTP was sensitive to D1 receptor antagonism. Pretreating slices for 10 min with SCH23390 (10 mM) fully blocked the GBR12783-enhanced LTP in all BLA principal neurons tested (13464%, n = 5, 3 animals, P,0.001, Figure 4, hooped bar). Next, we tested whether exogenous application of the D1 receptor agonist, SKF38393 (50 mM), could also facilitate LTP. Pretreatment with SKF38393 for 10 minutes prior to 5xHFS PLoS ONE | www.plosone.org 4 October 2011 | Volume 6 | Issue 10 | e26065