Fast-spiking (FS) and regular-spiking (RS) interneurons (INs) are electrically connected and can be separated into their respective types based on the characteristics of their activity. (A) Representative action potential (AP) traces of gap junction coupled layer 5 (L5) cortical GAD67 positive INs: FS and RS. (B) Input-output relationship for FS (white circles) and RS (black triangles) neurons (p < 0.0012, FS 243.8 ± 21.5, RS 121.5 ± 36.0). Quantification of AP; (C) amplitude (p = 0.055, FS 62.8 ± 1.19 mV, RS 67.5 ± 2.33 mV); (D) rise-time (p < 0.0014, FS 209.4 ± 6.46 μs, RS 252.1 ± 11.6 μs); (E) half-width (p < 0.0001, FS 664.5 ± 31.96 μs, RS 1426 ± 67.68 μs); (F) After-hyperpolarization potential (AHP) amplitude (p < 0.0001, FS 15.8 ± 0.56 mV, RS 8.7 ± 0.74 mV); (G) time to AHP peak (p < 0.0001, FS 2.9 ± 0.10 ms, RS 15.7 ± 0.55 ms); (H) AP threshold (p = 0.73, FS −37.4 ± 0.72 mV, RS −37.0 ± 0.97 mV); (I) rheobase (p < 0.05, FS 153.1 ± 9.50 pA, RS 111.8 ± 9.40 pA); (J) input resistance (p < 0.0001, FS 155.1 ± 10.5 MΩ, RS 242.0 ± 15.4 MΩ); and (K) time constant (p = 0.47, FS 17.3 ± 1.46 ms, RS 15.4 ± 1.54 ms). Data are presented as mean ± SEM. *p < 0.05.