Positron Emission Tomography Assessment of the Central Nervous System Effects of Eszopiclone and Zolpidem

Inclusion Criteria: * Healthy Males age 18 to 35 inclusive * Body Mass Index 18 to 30 * Willing to adhere to prohibitions and restrictions specified in protocol * Must give informed consent. Exclusion Criteria: * Clinically significant abnormal lab values for chemistry, hematology or urinalysis at screening. * Clinically significant abnormal physical exam, vital signs, or 12-lead EKG at screening * Significant history of or current significant medical illness. * Significant history of or current psychiatric or neurological illness or sleep apnea. * Participation in another research study involving exposure to ionizing radiation within the last 12 months. * Any clinically significant MR abnormality which may be relevant to the study. * Metal implants which are relevant for MR or PET procedures or data. * History of epilepsy or fits or unexplained blackouts. * Serology positive for Hepatitis B surface antigen, Hepatitis C antibodies, or HIV antibodies. * Positive urine screen for drugs of abuse. * Positive alcohol screen. * Known or suspected alcoholism or drug addiction even if currently abstaining * Drinks on average more than 8 cups of coffee, tea, cocoa, or cola per day. * Smoking cigarettes within 3 months prior to study drug administration. * Clinically significant acute illnes within 7 days of study drug administration. * Claustrophobia. * Donation of 1 or more units of blood (approximately 450ml), or acute loss of an equivalent amount of blood within 90 days prior to study drug administration. * Have received an experimental drug or used an experimental medical device within 90 days of planned start of treatment with drugs for this study. * Use of any prescription or over the counter medication, or herbal medication (not including non-steroidal anti-inflammatory drugs) within 2 weeks of the first PET scan. Of particular concern would be GABA-ergic compounds and CYP3A4 inhibitors. Exclusion should also be considered if the subject has taken a drug with a long half-life (or of any metabolite) even if taken outside the two week time window. However, the subject can still be enrolled if, in the opinion of the investigator, such medication taken in that timeframe will not interfere with the results of the study. * Psychological or emotional problems that would render the informed consent invalid or limit the ability of the subject to comply with the study requirements. * Any condition that in the opinion of the investigator would complicate or compromise the study, or the well-being of the subject.