Figure 5. Electrophysiological characteristics of BC-3b.

BC-3b is morphologically indistinguishable from type 3a (A), but it can be differentiated from the latter by the expression of the RIIβ-subunit of PKA (B, arrows). Furthermore, BC-3b displayed slowly inactivating L-type Ca²⁺ currents sensitive to nifedipine (C,D), but lacked evident HCN currents (E). In response to glutamate, BC-3b generated a bi-phasic response consisting of a transient current peak followed by a sustained component of smaller amplitude (F). Inhibitory feedback to glutamate stimulation was evident at 0 mV (G), generating a prolonged hyperpolarization under zero-current clamp after an initial depolarizing response peak (H).