Effect of D-cycloserine on Extinction of Fear Conditioning

Brief summary

Reproduced verbatim from the official ClinicalTrials.gov record. Not medical advice.

This study will evaluate whether the drug D-cycloserine (DCS) can improve a type of learning called classical conditioning, in which the brain learns to associate neutral stimuli with stimuli that elicit emotional or physiological responses. DCS is an antibiotic that was initially approved to treat tuberculosis and has been tested in clinical trials over the last decade for enhancing cognitive function. This protocol includes both a pilot study and a main study. The main study will begin after the pilot study ends. Healthy normal volunteers between 18 and 45 years of age may be eligible for these studies. Candidates will be screened with a medical and psychiatric history and a physical examination that includes blood and urine samples, an electrocardiogram (EKG), hearing test and startle test. The startle test involves recording eyeblink responses to loud noises. After the screening visit, those enrolled will participate in the pilot or main study, in which their reactions to two types of stimuli-an unpleasant, but harmless, shock to the arm and a mild puff of air to the eye-will be measured and recorded. \- Pilot Study Session 1 - Participants will receive very brief electric shocks delivered through two electrodes attached to the forearm or fingers and will hear brief loud sounds that may startle. Geometric shapes will be presented on a computer monitor. Sessions 2 and 3 - The procedure is the same as in session 1, except participants will also be subjected to brief low-intensity tones and airpuffs to the eye. \- Main Study Participants will undergo the same procedures described in the pilot study, with the following additions: * They will have an intravenous tube placed in a vein for collecting blood during the test. * They will take a pill each test day that contains either 100 mg DCS, 500 mg DCS, or a placebo (inactive substance). Subjects assigned to receive DCS will get the active drug on only one of the three test sessions and will be given placebo the other two sessions. The placebo group will receive placebo all three sessions. In both the pilot and main study, subjects' physiological responses to the stimuli will be recorded. Electrodes will be placed on two fingers (to measure sweat, or electrodermal activity), on the ribcage midway between the waist and armpit (to measure heart rate), and under one eye (to measure eye blink). Pulse will be recorded with a device attached to a finger, and breathing rate will be recorded with a special belt placed around the chest. At various times during the sessions, subjects will fill out questionnaires about their experience. Participants may withdraw from the study at any point.

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Last update posted Jul 1, 2017 · Synced Sep 11, 2026

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