Figure 4.

Correlation between channel activity and message level was specific for α_1D mRNA. (A) Relationship between L-type Ca²⁺ channel activity and L-type α_1D subunit mRNA level (estimated by RT-PCR) across individual neurons. A significant positive correlation (r_s = 0.64, P < 0.05, Spearman's nonparametric test) was found between rank orders of L-VSCC activity and α_1D mRNA level across individual cells. On the vertical axis, cells were ranked according to mRNA level. On the horizontal axis, the same cells were ranked according to channel activity. (B) No significant correlation (r_s = 0.07; n.s.; Spearman's nonparametric test) was found between calmodulin (CaM) mRNA level and L-type Ca²⁺ channel activity in a subset of the same cells as A.