Project Identifier: BNL-92-243
Project Title:
Dopamine D2 Receptor Availability Measured with Carbon-11-Labeled Raclopride
Principle Investigator:
Dr. Steven L. Dewey
Project started in: 1992
Project Funding Information:
Project received funding in Fiscal Year 1995.
Project used human subjects in Fiscal Year 1995.
Funding Sources:
DA 06891
Total Funding: $368,000
Project does not involve use of multiple protocols/subprojects.
IRB Review:
Type of Review: Full Board
Most Recent Approval: January 04, 1995
Number of Human Subjects in the Last Reporting Period for this Project: 23
(Reporting periods vary.)
Type of Human Subjects Involvement:
Internal administration of radioactive substances to human subjects.
These studies are designed to assess the availability of the dopamine D2 receptor in the human brain as it relates to the concentration of endogenous dopamine. The radiotracer, 11-C-raclopride, has been shown to be sensitive to changes in endogenous dopamine and we will use this reaction to probe the effects of changes in endogenous dopamine that are induced by different drugs using high resolution positron emission tomography (PET). The studies may provide insight into the mechanisms of actions of these drugs and may also help us understand the interactions that exist between the dopaminergic system and other systems that are anatomically linked to it. Approximately 15 normal volunteers, 15 alcoholic patients, 15 psychiatric patients, and 15 cocaine abusers will be studied using 11-C-raclopride and methylphenidate. The subjects will be males between the ages of 18-85. The subjects will have the short-lived positron emitter tracer (C-11-raclopride) administered intravenously and then be scanned with PET.
A potential side effect of radiation is the induction of cancer. However, no harm in a human individual or in a large population exposed at doses as low as those delivered in this procedure has been reported. The estimation of risk of harm can be obtained only from extrapolation from much higher doses. Methylphenidate is a mild central nervous system stimulant used to treat attention deficit disorder and narcolepsy. It increases heart rate and blood pressure and can cause a behavioral high. It can also elicit negative feelings of anxiety. In the event that either cardiovascular or behavioral complications occur, they can be effectively treated with an intramuscular injection of a neuroleptic. Since methylphenidate will be administered intravenously, the likelihood of cardiac stimulation is higher. There is also some evidence that methylphenidate may lower the seizure threshold in some individuals with no history of seizure disorders. Therefore, methylphenidate should not be given to patients with cardiac disease or patients with a past history of seizure disorders. Arterial catheterization has the following rare, but possible complications: pain during placement of the catheter, a risk of bleeding at the skin puncture site, the possibility of local infection and temporary or permanent impairment of the blood supply to portions of the hand. Whenever blood is removed or a substance is injected by venipuncture, there is minor discomfort and a slight possibility of local bleeding in the tissues.