The Role of Histone Deacetylases in Neurodegenerative Diseases and Small-Molecule Inhibitors as a Potential Therapeutic Approach.- Phosphodiesterase Inhibition to Target the Synaptic Dysfunction in Alzheimer’s Disease.- Glutamate and Neurodegenerative Disease.- Modulation of the Kynurenine Pathway for the Potential Treatment of Neurodegenerative Diseases.- Spinal Muscular Atrophy: Current Therapeutic Strategies