Fig. 6.

Leptin increases the density of filopodia via a MAPK-, but not PI 3-kinase-, driven pathway. (A, B) Confocal images of F-actin staining in hippocampal neurons (10–11 DIC) labeled with Alexa 488-conjugated phalloidin. The magnified regions of interest (white boxes) are illustrated below the parent images. (Ai) Incubation with wortmannin (50 nM; 1 h) had no effect on the density of filopodia per se, and it did not affect the ability of leptin to increase the number of filopodia. In contrast, prior incubation with PD98059 (10 μM; 1 h) attenuated leptin-induced increase in filopodial density (Bii). The density of filopodia was not altered in neurons exposed to PD98059 (Bi). (C) Histogram of pooled data illustrating the mean number of filopodia in control conditions and in neurons exposed to leptin (50 nM; 30 min) both alone and in the presence of wortmannin (WM; 50 nM), LY294002 (LY; 10 μM), PD98059 (PD; 10 μM) and U0126 (UO; 1 μM).