Entorhinal Cortex/physiology; Hippocampus/physiology; Neural Pathways/physiology; Action Potentials/drug effects; Action Potentials/physiology; Animals; Axons/drug effects; Axons/physiology; Dentate Gyrus/anatomy & histology; Dentate Gyrus/drug effects; Dentate Gyrus/physiology; Electric Stimulation; Entorhinal Cortex/anatomy & histology; Entorhinal Cortex/drug effects; Female; Hippocampus/anatomy & histology; Hippocampus/drug effects; Ketamine/pharmacology; Memory/physiology; Neural Pathways/anatomy & histology; Neural Pathways/drug effects; Pyramidal Cells/drug effects; Pyramidal Cells/physiology; Rats; Rats, Wistar; Reaction Time/drug effects; Reaction Time/physiology; Synapses/drug effects; Synapses/physiology; Synaptic Transmission/drug effects; Synaptic Transmission/physiology; Urethane/pharmacology; Xylazine/pharmacology