Interconversion of intrinsic bursters and nonbursters by I_NaP injection via DC. I_NaP predicted by Model 1 was added to nonbursters (G_NaP > 0) or subtracted from bursters (G_NaP < 0) via DC. The recordings were obtained under bath-applied Cd²⁺ (200 µM) and CNQX (20 µM). (A) CC recording from a representative nonburster. The neuron was verified to fire repetitively when sufficiently depolarized by injecting bias current (not depicted). (B) Same cell as in A, but with I_NaP added. When sufficient I_NaP is injected (G_NaP = 1.3 nS), the neuron exhibits robust bursting, with the bAHP and the interburst depolarization drift (arrow) characteristic of intrinsic bursters (Fig. 1 D). (C) Bursting frequency depends on baseline membrane potential (changed via depolarizing bias current, not depicted), a behavior typical of intrinsic bursters. A similar outcome was observed in all tested neurons (n = 24). The statistics for measured parameters characterizing oscillatory bursting are given in Table 2. (D) CC recording from a representative intrinsic burster. The neuron was verified to have the typical voltage-dependent bursting frequency (data not shown), as illustrated in Fig. 1 D. (E) Same cell as in D, but with I_NaP subtracted. The step changes in membrane potential V_m and I_NaP reflect depolarizing bias current steps of 5–10 pA. I_NaP subtraction eliminates the ability to generate bursting activity, but the neuron can fire repetitively when sufficiently depolarized. A similar outcome was observed in all tested neurons (n = 7).