Figure 3. Food restriction induces autophagy in cortical neurons and Purkinje cells.

Panel A. Autophagosomes (bright green punctae) in cortical neurons (left) and Purkinje cells (right) of GFP-LC3 mice after 48 hrs of food restriction. Panel B. Images of cerebellar sections stained with an antibody specific for phospho-S6RP (red), a protein whose abundance varies directly with mTOR activity, and inversely with autophagy. GFP-LC3, which is expressed at high levels in Purkinje cells, is shown in green and nuclei are stained with Hoechst dye (blue). Purkinje neurons in a normal fed animal (left) have high mTOR activity (indicating low autophagy) while cells in the 48 hrs food-restricted animal (right) have low mTOR activity (and, thus, a highly active autophagy pathway). Images were generated using Imaris software, blended mode (Bitplane, Inc). Panel C. A transmission electron microscope image of a single Purkinje cell from a 48 hour food-restricted mouse is shown. Autophagosomes are enclosed in colored boxes, and a higher-magnification image of each is provided.