Age Factors, Analysis of Variance, Animals, Behavior, Animal, Brain, Chromosomes, Artificial, Bacterial, Disease Models, Animal, Disease Progression, Gene Expression Regulation, Histones, Humans, Huntingtin Protein, Huntington Disease, Membrane Potentials, Mice, Mice, Transgenic, Microscopy, Electron, Transmission, Mutation, Nerve Tissue Proteins, Neurons, Nuclear Proteins, Patch-Clamp Techniques, Peptides, Subcellular Fractions