Fig. 1. Responses to depolarising and hyperpolarising current pulses in type 1 and type 2 Dahlgren cells recorded intracellularly from SWA and FWA preparations. (Ai,ii) Both SWA (i) and FWA (ii) cells fire in response to a depolarising current pulse (+0.9 nA, 300 ms) and on the rebound following a hyperpolarising (-0.9 nA, 300 ms) pulse. (B) Voltage-dependent sag potentials (dotted lines) and depolarizing afterpotentials (DAP, arrow) recorded from a type 1 FWA cell in response to hyperpolarising square-wave current injection (-1.2 nA, 300 ms). The membrane potential was held at three levels [-50, -60 (RMP) and -70 mV] by constant current injection. At the more depolarised potential, the DAP triggered an action potential. RMP, resting membrane potential.