Effects of a CRF1 Receptor Antagonist on Human Startle in Normal Female Volunteers

Background: \- Research has shown that the hormone corticotropin-releasing hormone (CRH) is involved in stress and anxiety, and that drugs that block the effect of CRH in the body can reduce anxiety. GSK561679 is an experimental drug that attempts to reduce anxiety by blocking the effect of CRH. Researchers are interested in comparing GSK561679 with other treatments for anxiety. Objectives: \- To determine the effectiveness of GSK561679 compared with placebo and alprazolam (Xanax), as a possible treatment for fear and anxiety. Eligibility: \- Healthy female volunteers between 21 and 50 years of age. Design: * This study will involve one screening visit, four testing visits, and one follow-up visit over a period of 8-9 weeks. The testing sessions will be between 6-11 days apart. * Participants must follow these dietary restrictions to participate in the study. * No nicotine, alcohol, or caffeine (including chocolate and soft drinks) for 24 hours before the start of the study. * No nicotine in the past 6 months, and no nicotine until the final blood sample is collected at the follow-up visit. * No alcohol or caffeine for 24 hours before a testing visit or for 72 hours after each visit. * No grapefruit or grapefruit products from 14 days before the first dose of study medication until collection of the final blood sample. * Participants will receive a dose of GSK561679, alprazolam, or placebo 3 hours before the testing, and will take an additional pill 1 hour before the testing. * During the tests, participants will receive brief electric shocks and hear sudden loud noises. The noises and shocks will be given over a period of approximately 40 minutes per session. * Skin conduction, heart rate, and blinking will be monitored throughout the tests, and participants will be asked about anxiety levels and will be tested on mood, memory, and concentration. Blood and saliva samples will also be taken during these sessions. * Participants will stay in the clinical cente