Figure 2.

GnRH-induced Ca²⁺ sparklets are mediated by L-type Ca²⁺ channels and promote ERK activation. A and C, Representative traces showing time courses of Ca²⁺ influx in an αT3–1 cell before and after application of the L-type Ca²⁺ channel agonist FPL 64176 (500 nM) (A) and GnRH (3 nM) (C) in the presence of the L-type Ca²⁺ channel antagonist nicardipine (10 μM). B and D, Plots of Ca²⁺ sparklet site activities (nP_s) and mean ± SEM Ca²⁺ sparklet site densities (Ca²⁺ sparklet sites per square micrometers) before and after FPL 64176 (n = 12 cells) (B) and GnRH in the presence of nicardipine (n = 7 cells) (D). E, Western blot analysis of ERK activation (as measured by ERK phosphorylation) in αT3–1 cells exposed to GnRH (3 nM) or FPL 64176 (500 nM) in the presence of nicardipine (10 μM) for 5 or 10 minutes (n ≥ 3 independent experiments). *, P < .05 vs nicardipine; †, P < .05 vs nicardipine and P < .05 vs GnRH. cont, control; nic, nicardipine.