Figure 2.

HVA Ca²⁺ currents in acutely isolated thalamic relay neurons. A, Representative traces of total Ca²⁺ currents of control, α1A^–/–/α1G^+/+, and α1A^–/–/α1G^–/– TC neurons evoked by stepping membrane potential voltages between –10 and +10 mV in 10 mV increments from a holding potential of –60 mV. Sustained HVA Ca²⁺ currents decayed slowly during the 200 msec step commands. B, Mean peak I–V curves for total Ca²⁺ currents in TC neurons show different features between the two groups. The I–V relationship at this voltage protocol shows that the HVA Ca²⁺ currents in α1A^–/–/α1G^+/+ cells were dramatically reduced at all testing voltage steps above –40 mV compared with those in control. Symbols represent pooled data from α1A^–/–/α1G^+/+ (open symbols; n = 8) and control mice (filled symbols; n = 10). C, The HVA Ca²⁺ histogram of peak amplitude is at –10 mV in control (black bars; n = 10), α1A^–/–/α1G^+/+ (gray bars; n = 12), and α1A^–/–/α1G^–/– (white bars; n = 11), with holding potential at –60 mV. Note that the peak amplitude of HVA Ca²⁺ currents in α1A^–/–/α1G^+/+ and α1A^–/–/α1G^–/– mice was decreased significantly more than in α1A^+/+/α1G^+/+ mice(*p<0.001; two-tailed t test). No statistically significant changes occurred in the HVA Ca²⁺ current of α1A^–/–/α1G^–/– mice compared with that from TC neurons of α1A^–/–/α1G^+/+ mice (p > 0.05). Control indicates α1A^+/+/α1G^+/+.