Figure 2. Sinusoidal subthreshold oscillations (SSTOs) and rebound potentials in wild-type, Ca_V2.1^−/− and Ca_V3.1^−/− mice.

A, representative SSTOs at five membrane potentials (at left of each trace) in wild-type, Ca_V2.1^−/− and Ca_V3.1^−/− mice in the presence of TTX. Oscillations were present at all membrane potential levels in all genotypes, although they were lowest in Ca_V3.1^−/− mice. B, SSTO amplitude plotted as a function of cell membrane potential. (Mean amplitudes were scaled to the largest response taken as 100%.) Note that SSTO amplitude is modulated in wild-type and Ca_V2.1^−/−, but not Ca_V3.1^−/− mice. C, SSTO frequency as a function of cell membrane potential. Note also that frequency was lower in the mutant mice, and that frequency was insensitive to membrane potential in wild-type and mutant mice. Data in B, C and D were obtained from the same cells. D, the intracellular injection of a hyperpolarizing current pulse (−0.8 nA, 0.2–0.3 s) from the resting or hyperpolarized membrane potentials elicited a low-threshold spike and rhythmic oscillations in IO neurons from wild-type (black) and Ca_V2.1^−/− (red), but not Ca_V3.1^−/− (blue) mice, although the rebound activity mediated by the hyperpolarization-activated cation current (I_h) was present.