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. 2016 Jul 20;41(12):2862–2871. doi: 10.1038/npp.2016.98

Figure 4.

Figure 4

Conditioned fear triggers an increased density and a gain of function of adenosine A2A receptors (A2ARs) in the amygdala. The comparison of the binding density of the selective A2AR antagonist 3H-SCH58261 (3H-5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazolo-[1,5-c]pyrimidine, 3 nM) to membranes prepared from control mice (open bars) and from fear conditioned mice 2 days (a) or 8 days (b) after fear conditioning (filled bars) revealed an increased A2AR density in the amygdala (Amyg), hippocampus (HIP), and ventral striatum (vSTR), but not in the dorsal striatum (dSTR), of fear-stressed mice. This fear stress-induced upregulation seems selective for A2ARs as there was no similar modification of A1R density, as evaluated by the binding density of the selective A1R antagonist 3H-DPCPX (3H-1,3-dipropyl-8-cyclopenthylxanthine; 6 nM) in membranes from fear-stressed mice 2 days (c) or 8 days (d) after fear conditioning (filled bars) compared with control mice (open bars). Data are mean±SEM of nine mice per group for analysis of A2AR density and n=4–5 mice per group for the analysis of A1R density. *p<0.05 compared with control (open symbols), unpaired Student's t-test. (e) The blockade of A2ARs with SCH58261 (50 nM) still effectively decreased long-term potentiation (LTP) amplitude recorded extracellularly in the lateral amygdala triggered by a high-frequency stimulation (HFS) train in external capsula of slices collected 8 days after fear conditioning; (f) such an effect that was not observed in slices collected 8 days after fear-stressed mice that were injected bilaterally in the amygdala 3 weeks before with lentivectors expressing a short hairpin RNA (shRNA) to neutralize A2ARs (shA2AR). Data are mean±SEM of four to five mice per group, unpaired Student's t-test. (g) Comparison of LTP amplitude before and 8 days after induction of fear conditioning. (h) Comparison of the impact on LTP amplitude of the different manipulations of A2ARs before and 8 days after induction of fear conditioning.