Effects of Prazosin on the Attention-Enhancing Effects of Nicotine

Inclusion Criteria: * Aged 21 to 55 years. * Smoked no more that 40 cigarettes, cigars or cigarillos in lifetime. * Smoked no cigarettes, cigars or cigarillos in the last year. * No exposure to any nicotine-containing product in the last month. * Normal or corrected to normal vision (at least 20/80). Exclusion Criteria: * Pregnant or breast-feeding. * Drug or alcohol abuse or dependence currently or in the last 2 years. * DSM Axis I mood, anxiety or psychotic disorder. * Cardiovascular or cerebrovascular disease. * Hypertension (resting systolic BP above 150 or diastolic above 95 mm Hg). * Hypotension (resting systolic BP below 90 or diastolic below 60). * Bradycardia (heart rate \<60 bpm). * Impaired liver or kidney function. * Severe asthma. * Obstructive pulmonary disease. * Type I diabetes. * Use of any centrally active medications. * Use of any cardiovascular drugs, including blood pressure medications and antiarrhythmics. * Use of diuretic medication. * History of or current neurological illnesses, such as stroke, seizure disorders, neurodegenerative diseases, or organic brain syndrome. * Learning disability, mental retardation, or any other condition that impedes cognition. * Planned eye surgery. * Inability to perform the Rapid Visual Information Processing Task. * Known hypersensitivity to prazosin, any quinazolines, or nicotine. * Narcolepsy.