Rebalancing the Serotonergic System in Cocaine Dependence

Inclusion Criteria: * \- Participants will be male and female volunteers between the ages of 18-55 * Participants will report having used cocaine on at least four occasions within the month prior to screening; the urine sample obtained during the screening visit must be positive for the cocaine metabolite benzoylecgonine (\>300 ng/ml). They can meet DSM-IV criteria for cocaine abuse and dependence. * Participants cannot meet DSM-IV criteria for current psychotic disorders (e.g., bipolar disorder, schizophrenia, schizoaffective disorder) * Participants cannot meet DSM-IV criteria for a current major depressive episode * Participants cannot meet DSM-IV criteria for current drug dependence (except nicotine, cocaine, and marihuana) * Participants must test negative for alcohol use on the day of the scan. * Participants can report current abuse of marihuana and tobacco. Participants cannot have used marihuana within twelve hours of their study visits. * Participants cannot be regular opiate users including prescription opiate analgesics * Participants cannot have a history of major head trauma resulting in cognitive impairment, seizure, or other neurological disorders. * Participants cannot have any conditions that are contraindicated for MRI (see next section) * Participants cannot be pregnant (pregnancy test will be performed before each scanning session) * Participants must be able to read screening materials including consent form and give informed consent * Participants cannot be taking any medications with a 5-HT mechanism including serotonin-norepinephrine reuptake inhibitors (SNRIs), selective serotonin reuptake inhibitors (SSRIs), tricyclic antidepressants (TCAs), monoamine oxidase inhibitors (MAOIs) and St. John's Wort and tryptophan. * Participants cannot be currently taking any medications that might affect the central nervous system including prescription analgesics, anxiolytics, antipsychotics, and antidepressants. A complete review of medications will be evaluated by study staff. * Cannot have any history of a medical condition that might affect the central nervous system at the time of scanning including: Abnormal structural MRI, or a history of head trauma or injury causing loss of consciousness lasting longer than 3 minutes or associated with skull fracture or intracranial bleeding or who had irremovable magnetically active objects on or within their body, or history of epilepsy. Exclusion Criteria: * \- Weight greater than 350 pounds (cannot easily fit inside the magnet bore) * Cardiac pacemakers * Aneurysm clips and other vascular stents, filters, clips or other devices * Prosthetic heart valves * Other prostheses * Neuro-stimulator devices * Implanted infusion pumps * Cochlear implants * Ocular implants or known metal fragments in eyes * Exposure to shrapnel or metal filings (sheet metal workers, welders, and others) * Other metallic surgical hardware in vital areas * History of major head trauma resulting in cognitive impairment * Certain tattoos (e.g. older dye with metallic pigment) * Certain medication patches (if they cannot be removed) * Metal containing IUDs * Claustrophobia * Pregnancy * Metallic implants except fillings and crowns * Tattoos containing metallic ink on the neck, shoulders, upper arm, and head (these could become heated during scanning, potentially causing burns * Medication patches that cannot be removed during scanning * Claustrophobia