Down Syndrome/complications; Down Syndrome/pathology; Hippocampus/pathology; Learning Disabilities/drug therapy; Neurons/physiology; Receptors, GABA-A/metabolism; Acoustic Stimulation; Analysis of Variance; Animals; Benzodiazepines/pharmacology; Benzodiazepines/therapeutic use; Biophysics; Carrier Proteins/metabolism; Cell Count; Cell Proliferation/drug effects; Cues; Disease Models, Animal; Down Syndrome/drug therapy; Electric Stimulation; Excitatory Postsynaptic Potentials/drug effects; Excitatory Postsynaptic Potentials/genetics; Exploratory Behavior/drug effects; GABA Modulators/pharmacology; GABA Modulators/therapeutic use; Glutamate Decarboxylase/metabolism; Hippocampus/drug effects; Hyperkinesis/drug therapy; Hyperkinesis/etiology; Imidazoles/pharmacology; Imidazoles/therapeutic use; Ki-67 Antigen; Learning Disabilities/etiology; Long-Term Potentiation/drug effects; Long-Term Potentiation/genetics; Male; Maze Learning/drug effects; Membrane Proteins/metabolism; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neurogenesis/drug effects; Neurogenesis/genetics; Neurons/drug effects; Protein Binding/drug effects; Protein Binding/genetics; Psychomotor Performance/drug effects; Reaction Time/drug effects; Reflex/drug effects; Reflex/genetics; Reflex, Startle/drug effects; Rotarod Performance Test; Seizures/etiology; Sensory Gating/drug effects; Tritium/pharmacokinetics; Vesicular Inhibitory Amino Acid Transport Proteins/metabolism