Positron Emission Tomography (PET) Study of Brain Calcitonin Gene-Related Peptide (CGRP) Receptor Occupancy After Telcagepant Administration (MK-0974-067)

Participant is mentally or legally incapacitated, has significant emotional problems at the time of prestudy (screening) visit or expected during the conduct of the study or has a history of a clinically significant psychiatric disorder over the last 5 years (participant with situational depression in the past 6 to 12 months, but not currently, may be enrolled at the discretion of the investigator)

Participant has a history of any illness that, in the opinion of the study investigator, might confound the results of the study or poses an additional risk to the subject by their participation in the study

Participant has an estimated creatinine clearance of ≤80 mL/min

Participant has a history of stroke, chronic seizures, or major neurological disorder

Participant has a history of clinically significant endocrine, gastrointestinal, cardiovascular, hematological, hepatic, immunological, renal, respiratory, or genitourinary abnormalities or diseases

Participant has a history of neoplastic disease except 1) adequately treated non-melanomatous skin carcinoma or carcinoma in situ of the cervix 2) other malignancies which have been successfully treated ≥10 years prior to the prestudy (screening) visit where, in the judgment of both the investigator and treating physician, appropriate follow-up has revealed no evidence of recurrence from the time of treatment through the time of the prestudy (screening) visit

For Part III only: Participant is a nursing mother, has difficulty distinguishing his/her migraine attacks from tension or interval headaches, has a history of predominantly mild migraine attacks or migraines usually resolved spontaneously in less than 4 hours, has basilar or hemiplegic migraine headache, has more than 15 headache-days per month or has taken medication for acute headache on more than 10 days per month in any of the 3 months prior to screening, is taking migraine prophylactic medication, was \>50 years of at age of migraine onset, has, in the opinion of the investigator, other confounding pain syndromes, psychiatric conditions such as uncontrolled major depression, dementia or significant neurological disorders other than migraine, has liver function tests, specifically alanine aminotransferase (ALT)/aspartate aminotransferase (AST) and Alkaline Phosphatase are above the upper limit of normal at the prestudy (screening) visit or at recheck within 4 weeks prior to Day 1, is taking strong or moderate Cytochrome P450 3A4 (CYP3A4) inhibitors such as Ketoconazole, Diltiazem or Verapamil

Participant is unable to refrain from or anticipates the use of any medication, including prescription and non-prescription drugs or herbal remedies

Participant consumes excessive amounts of alcohol

Participant consumes excessive amounts, defined as greater than 6 servings of caffeinated beverages per day

Participant has had major surgery, donated or lost 1 unit of blood (approximately 500 mL) or participated in another investigational study within 4 weeks prior to the prestudy visit

Participant has a history of significant multiple and/or severe allergies (including latex allergy), or has had an anaphylactic reaction or significant intolerability to prescription or non-prescription drugs or food

Participant is currently a regular user (including "recreational use") of any illicit drugs or has a history of drug (including alcohol) abuse within approximately 2 years

Participant has participated in a PET study or other study involving administration of a radioactive substance or ionizing radiation within 12 months prior to the prestudy visit

Participant has implanted or embedded metal objects or fragments in the head or body that would present a risk during the magnetic resonance imaging (MRI) scanning

Participant suffers from claustrophobia and would be unable to undergo MRI or PET scanning

Any concern by the investigator regarding the safe participation of the participant in the study, and the ability of the subject to tolerate the procedures.

What this study is about