Figure 4. IGF-1 enhances HVA Ca²⁺ channel currents in young adult rats.

Representative Ca²⁺ channel current records from -30 to 30 mV with 20 mV intervals in control (A) and IGF-1-treated (B) pyramidal motor neurons. C, Ca²⁺ channel current-voltage relationship in control (filled circles) and after treatment with 20 ng ml⁻¹ IGF-1 (open circles). Experimental data were fitted to eqn (1). Average best-fit parameters are shown in Table 1. Asterisks indicate statistically significant difference (P < 0.05). D, RT-PCR for HVA Ca²⁺ channel α₁ expression in brain motor cortex. M and A-S indicate the lanes in which the marker and undigested Ca²⁺ channel cDNAs, respectively, were loaded. E, effects of acute perfusion of a channel blocker alone or in combination with IGF-1 on the peak Ca²⁺ channel current. Bars represent means ± s.e.m. of the ratio between the peak Ca²⁺ channel current recorded in the presence and absence of a channel blocker (grey bars) and the ratio between the effect of the combination of a Ca²⁺ channel blocker plus IGF-1 and a Ca²⁺ channel blocker alone on the peak Ca²⁺ channel current (black bar). Asterisks indicate the statistical significance (P < 0.05).