Glutamic Acid/metabolism; Hippocampus/metabolism; Interneurons/metabolism; Neuronal Plasticity/physiology; Parvalbumins/metabolism; Receptor, Cannabinoid, CB1/metabolism; Synapses/metabolism; Animals; Calcium Signaling/drug effects; Calcium Signaling/physiology; Cell Polarity/drug effects; Cell Polarity/physiology; Cell Shape/physiology; Dendrites/drug effects; Dendrites/metabolism; Dendrites/ultrastructure; Hippocampus/cytology; Hippocampus/drug effects; Immunohistochemistry; Interneurons/cytology; Interneurons/drug effects; Long-Term Potentiation/drug effects; Long-Term Potentiation/physiology; Long-Term Synaptic Depression/drug effects; Long-Term Synaptic Depression/physiology; Male; Neural Inhibition/drug effects; Neural Inhibition/physiology; Neuronal Plasticity/drug effects; Organ Culture Techniques; Patch-Clamp Techniques; Presynaptic Terminals/drug effects; Presynaptic Terminals/metabolism; Presynaptic Terminals/ultrastructure; Rats; Rats, Sprague-Dawley; Receptor, Cannabinoid, CB1/drug effects; Receptors, AMPA/drug effects; Receptors, AMPA/metabolism; Synapses/drug effects; Synapses/ultrastructure; Synaptic Transmission/drug effects; Synaptic Transmission/physiology; gamma-Aminobutyric Acid/metabolism