Adaptor Proteins, Signal Transducing; Brain-Derived Neurotrophic Factor/physiology; Calcium-Calmodulin-Dependent Protein Kinases/physiology; Receptor Protein-Tyrosine Kinases/physiology; Receptors, Nerve Growth Factor/physiology; Signal Transduction/physiology; ras Proteins/physiology; src Homology Domains/physiology; 3T3 Cells; Amino Acid Sequence; Animals; Base Sequence; Brain/physiology; Brain-Derived Neurotrophic Factor/metabolism; COS Cells; Calcium-Calmodulin-Dependent Protein Kinases/metabolism; Cell Differentiation/physiology; Cell Division/physiology; Cell Survival/physiology; DNA, Complementary/genetics; DNA, Complementary/isolation & purification; Epidermal Growth Factor/metabolism; Epidermal Growth Factor/physiology; ErbB Receptors/metabolism; ErbB Receptors/physiology; GRB2 Adaptor Protein; Humans; Mice; Molecular Sequence Data; Neurons/cytology; Neurons/metabolism; Neurons/physiology; Phosphorylation; Proteins/metabolism; Proteins/physiology; Receptor Protein-Tyrosine Kinases/metabolism; Receptor, trkB; Receptors, Nerve Growth Factor/metabolism; Sensitivity and Specificity; Sequence Homology, Amino Acid; Tyrosine/metabolism; ras Proteins/metabolism