(A1–D1) Principal neuron membrane potential response to injection of a sinusoidal current with constant amplitude and linearly changing frequency (0–12 Hz) in the presence of various drug cocktails. All neurons were held at baseline of −60 mV. (A1) Typical voltage response to the sinusoidal current in TTX (1 µM). The resonance of BLA principal neurons can be enhanced by application of 4-AP (B1, 500 µM) and the adenylyl cyclase activator, forskolin (C1, 10 µM), and is abolished by application of NiCl (500 µM, D1). Analysis of power spectra (E) shows that the enhancement of resonance by 4-AP and forskolin is significantly different from baseline (p<0.05). (A2–D3) Intrinsic membrane oscillations of BLA principal neurons, held at −60 mV, in response to a steady depolarizing current injection (A2–D2) and in response to the same current injection with superimposed IPSPs (A3–D3). Similar to resonant properties, membrane oscillations are enhanced by application of 4-AP and forskolin, and abolished in NiCl. Injection of artificial IPSPs in A3–D3 significantly enhanced the amplitude and duration of oscillations (F and G; spectrograms illustrate data from C2 and C3 respectively).