Endocytosis/physiology; Myosin Heavy Chains/physiology; Receptors, AMPA/metabolism; Synapses/physiology; Adaptor Protein Complex 2/metabolism; Adaptor Proteins, Signal Transducing; Adenosine Triphosphate/pharmacology; Animals; Astrocytes/metabolism; Astrocytes/ultrastructure; Brain/metabolism; Brain/ultrastructure; Brain Chemistry; Dendrites/metabolism; Dendrites/ultrastructure; Dendritic Spines/metabolism; Dendritic Spines/ultrastructure; Discs Large Homolog 1 Protein; Dyneins/genetics; Dyneins/metabolism; Endocytosis/drug effects; Female; Glial Fibrillary Acidic Protein/analysis; Guanylate Kinases; Insulin/pharmacology; Male; Membrane Proteins; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Microfilament Proteins/analysis; Microfilament Proteins/metabolism; Microscopy, Electron; Myosin Heavy Chains/genetics; Myosin Heavy Chains/metabolism; Myosin VIIa; Myosins/genetics; Myosins/metabolism; Nerve Tissue Proteins/analysis; Nerve Tissue Proteins/metabolism; Neurons/physiology; Neurons/ultrastructure; Receptors, AMPA/analysis; Receptors, Glutamate/metabolism; Sucrose/pharmacology; Synapses/ultrastructure; Synaptic Membranes/chemistry; Synaptic Membranes/drug effects; Synaptosomes/chemistry; Synaptosomes/drug effects; Transferrin/metabolism; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid/metabolism