Figure 3. Neurotransmission from Ivy cells is inhibited by DAMGO. A, In paired recordings between a presynaptic Ivy cell and a postsynaptic pyramidal cell, 1 μm DAMGO produced a strong inhibition of the IPSC. Shown on top is the presynaptic action potential and on bottom the postsynaptic response (gray, 20 individual sweeps; black, average) before drug addition, in the presence of DAMGO (1 μm), and after the addition of CTAP (500 nm) for a representative pair. Right, Overlay of the average response before drug (black), in DAMGO (blue), and after the addition of CTAP (red). Bottom left, The presynaptic cell (asterisk) expressed GFP (under the NPY promoter) and showed immunoreactivity for nNOS. Bottom right, Summary graph illustrating individual paired recordings (gray circles) and the average euIPSCs (black, error bars indicate SEM) per condition. B, In a subset of experiments, 1 μm DAMGO was applied for minutes before application of CTAP. Shown is an example pair for this, before drug addition (a, black trace in overlay), in DAMGO (b, blue trace in overlay), in the continued presence of DAMGO (c, gray trace in overlay), and after the addition of CTAP (d, red trace in overlay). Bottom left, The presynaptic cell (asterisk) expressed GFP and showed immunoreactivity for nNOS. The biocytin-filled postsynaptic pyramidal cell (p) is also visible. Bottom middle, Reconstruction of the presynaptic Ivy cell (dendrites black, axon red) and postsynaptic pyramidal cell (dendrites blue, axon gray). Bottom right, Time course of euIPSC amplitude and drug application. Note that the euIPSC amplitude remains depressed in the continued presence of DAMGO. C, In a separate set of experiments, CTAP was applied before 1 μm DAMGO application. Top, An example pair before drug addition (black in overlay), in the presence of CTAP (red in overlay), and after the addition of DAMGO (blue in overlay). Bottom left, The presynaptic Ivy cell (asterisk) expressed GFP and showed immunoreactivity for nNOS. The postsynaptic pyramidal cell is marked (p). Bottom right, Individual pairs (gray) and average (black) euIPSC amplitude per condition. D, In paired recordings between a presynaptic PV–TOM basket cell and a postsynaptic pyramidal cell, DAMGO inhibits the IPSC. Top, An example pair before drug addition (black in overlay), in the presence of 1 μm DAMGO (blue in overlay), and after the addition of CTAP (red in overlay). Bottom left, Summary graph illustrating individual paired recordings (gray circles), at 1 μm DAMGO concentration, and the average euIPSCs (black, error bars indicate SEM). Bottom right, Percentage reduction of the euIPSC amplitude from pairs with presynaptic NPY Ivy cells (green) or presynaptic PV basket cells (red) at 1 and 0.05 μm DAMGO concentrations. so, Stratum oriens; sp, stratum pyramidale; sr, stratum radiatum. Calibration: A–C, 10 ms, 10 pA or 10 mV; D, 10 ms, 10 mV or 50 pA. Scale bars: A–C, 10 μm; B, reconstruction, 50 μm.