(A, C) Images of horizontal slices taken from a CCK-DsRed and a PV-eGFP mouse, respectively, containing the basolateral amygdala region. Positions of the recorded BCs are shown in Figure 1—figure supplement 2. (B) Maximum z intensity projection image of a biocytin-filled CCKBC. Inset: Axon terminals of CCKBCs (blue) are immunopositive for type one cannabinoid receptor (CB1, magenta). (D) Maximum z intensity projection image of a biocytin-filled PVBC. Inset: Varicosities of PVBCs (blue) are immunopositive for calbindin. For more detailed neurochemical characterization of CCK-DsRed and PV-eGFP cells see Figure 1—figure supplement 1. (E and G) Representative voltage responses of a CCKBC (E, 400, –100 pA) and a PVBC (G, 300, –100 pA) upon step current injections. (F and H) Representative postsynaptic current (PSC, F2, H2) and postsynaptic potential (PSP, F3, H3) recordings in a CCKBC-PN (F) or in a PVBC-PN pair (H) in response to three action potentials evoked at 30 Hz (F1, H1). Ten superimposed consecutive traces in grey, averages in black. (I), PSPs recorded in a PN at different membrane potentials in gramicidin-based perforated patch recordings upon a train of 10 action potentials evoked at 40 Hz in a presynaptic PVBC. (J) The integral of the summed PSPs was calculated at each membrane potential and fitted with a second order polynomial curve to determine the reversal potential of the responses. (K) Comparison of the estimated reversal potential of PSP recorded in perforated patch and whole-cell patch-clamp mode using 4 mM Cl- intrapipette solution and the resting membrane potential of PNs revealed the inhibitory nature of the BC connections (CCKBC: perforated patch mode: −75.74 ± 2.44 mV, whole cell mode: −78.67 ± 1.55 mV, p=0.296, n = 5–5 pairs; PVBC: perforated patch mode: −72.17 ± 1.88 mV; whole cell mode: −75.79 ± 1.90 mV, p=0.403, n = 5–5 pairs, both M-W test; PN resting membrane potential: −60.13 ± 1.09 mV). (L–S) Comparison of basic electrophysiological properties of IPSCs (L–R), and IPSPs (S) at the output synapses of CCKBCs and PVBCs recorded in whole-cell mode. Horizontal line represents mean. For data see Figure 1—source data 1. Scales: A and C: 0.5 mm; B and D: 50 µm, insets: 2 µm; E and G: 10 mV, 200 ms; F and H x: 50 ms, F1 and H1 y: 30 mV, F2 and H2 y: 50 pA, F3 and H3 y: 1 mV, I: 0.5 mV (PN), 30 mV (BC) and 100 ms.