Central Nervous System/pathology; Mast Cells/metabolism; Neurogenic Inflammation/pathology; Nociceptors/pathology; Animals; Capsaicin/pharmacology; Carrageenan; Cell Count; Cell Degranulation/drug effects; Central Nervous System/physiopathology; Female; Hyperalgesia/complications; Hyperalgesia/pathology; Long-Term Potentiation/drug effects; Lumbar Vertebrae/drug effects; Lumbar Vertebrae/pathology; Lumbar Vertebrae/physiopathology; Male; Mast Cells/drug effects; Mast Cells/physiology; Nerve Fibers, Unmyelinated/drug effects; Nerve Fibers, Unmyelinated/pathology; Neurogenic Inflammation/complications; Neurogenic Inflammation/physiopathology; Nociceptors/drug effects; Nociceptors/metabolism; Rats; Rats, Sprague-Dawley; Synapses/drug effects; Thalamus/drug effects; Thalamus/pathology; Thalamus/physiopathology; Time Factors