Figure 2. DOR and MOR activation inhibits glutamate release at the BLA-ITC synapse.

(a) Post hoc confocal images of DAPI (blue) and biocytin-labelled ITCs (red/white). Low power image shows intense DAPI labelling with high cell density within Im. Single image; scale bar, 100 μm. Magnification (× 20 objective) of boxed area, shows two filled ITCs with bipolar characteristics. Stack image (z=13.5 μm); scale bar, 50 μm. Further magnification (× 63, boxed area) reveals dendritic spines (arrows); single Z section (z=2.5 μm); scale bar, 3 μm. (b) Representative BLA-Im stimulation and recording locations. (c–e) Selective DOR (deltorphin II, Delt 300 nM) and MOR (DAMGO, 1 μM)) agonists, reduced eEPSC amplitude and increased PPR that was reversed by the corresponding antagonists ICI1173864 (ICI, 1 μM) and CTAP (1 μM), respectively. KOR agonist (U69, 3 μM) and antagonist norBNI (10 nM), had no effect. (c) Example eEPSCs and time plot of normalized peak amplitude (eEPSC₁) of a single representative experiment. (d) Bar chart showing percentage inhibition from baseline. Baseline defined as eEPSC amplitude of CTL (no drug) or previous antagonist. (e) Bar chart showing PPR, calculated as eEPSC₂/eEPSC₁. (f–h) ME (10 μM) reduced eEPSC amplitude and increased PPR which fully reversed after wash. (f) Example eEPSCs and time plot of single representative experiment; (g) bar chart of mean inhibition during ME and wash. (h) Bar chart of mean PPR (bottom) and example traces (top) normalized to first eEPSC before (black) and during ME (grey). (i) ME inhibition was fully reversed by combined DOR and MOR antagonist treatment. Example eEPSCs and bar chart showing the proportion of ME inhibition of eEPSC amplitude (%) reversed by the selective antagonists. (Data are represented as mean±s.e.m.; *P<0.05, **P<0.01, paired t-test, from CTL; ^##P<0.01, paired t-test versus ME.) Highlighted regions on time plots represent region sampled for bar charts. Scale bars, 50 ms, 100 pA.