Fig. 5.

Correlation analysis of Ca_V α₁ subunit expression with individual β and α₂δ isoforms. Correlation coefficients were calculated between the transcript amounts of the individual α₁ and the auxiliary β and α₂δ subunits including measurements from all tissue and culture preparations. The abscissa represents the size and direction of the correlation coefficients whereby direct (positive) and indirect (negative) coefficients are indicated by green and red bars, respectively. Asterisks mark significant correlations and the gray area indicates the cut-off (r=0.4) for weak correlations. (A) Correlation analysis clearly identified the previously demonstrated association of the Ca_V2.1 α₁ subunit with β₄ and α₂δ-2. Interestingly, Ca_V1.2, Ca_V2.2, and Ca_V2.3 showed similar degrees of correlations with the same set of β and α₂δ subunits. Expression of Ca_V1.3 did not reveal a strong correlation with any auxiliary subunit. (B) Similar correlation coefficients were identified for Ca_V2.1 and Ca_V2.3 by including only the measurements from cultured hippocampal neurons. * P<0.05; ** P<0.01; Pearson correlation.