Fig. 3.

Insulin-like growth factor-1 (IGF-1) treatment prevents Foxo1 effects on action potential induced Ca²⁺ transients. Cultured fibers expressing GFP (A; n = 36, N = 4), fibers expressing Foxo1-GFP (B; n = 25, N = 4), and fibers expressing Foxo1-GFP treated with IGF-1 from the time of infection (for 48 h; C; n = 30, N = 4) were stimulated using the same pattern of stimulation as detailed in Fig. 2. N indicates number of mice per condition, and n indicates number of fibers tested. The vast majority of the Foxo1-GFP fibers treated with IGF-1 did not have compromised calcium transients as those seen in untreated fibers expressing Foxo1-GFP. D: average change in indo-1 ratio in response to electrical stimulation is significantly reduced in fibers expressing Foxo1-GFP compared with fibers expressing GFP alone or fibers expressing Foxo1-GFP and treated with IGF-1. *P < 0.05, compared with fibers expressing Foxo1-GFP and treated with IGF-1. E: distribution of Δindo-1 amplitude in response to a single stimulus in fibers expressing GFP, fibers expressing Foxo1-GFP, and fibers expressing Foxo1-GFP and treated with IGF-1. Percentage of Foxo1-GFP fibers treated with IFG-1 that exhibited a calcium transient, as defined by peak Δindo-1 ratio >0.1 in response to electrical stimulation is higher than that of Foxo1-GFP fibers.