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Home > "P" Clinical Trials Conditions > Positron Emission Tomography (PET) to Study Brain Signaling  Positron Emission Tomography (PET) to Study Brain Signaling
Positron Emission Tomography (PET) to Study Brain Signaling
For Condition: Healthy
Status: Recruiting
Sponsor(s): National Institute of Neurological Disorders and Stroke (NINDS) ,
Synopsis: This study uses positron emission tomography (PET) to examine how brain signaling is related to blood flow. Much of the brain is composed of fatty molecules called phospholipids. These molecules are involved in the way brain cells signal each other to direct brain function. In various diseases of the brain, phospholipids may change their properties, disturbing brain structure and cell communication. Studies of brain phospholipid composition and metabolism may help clarify how the brain works in healthy people or stops working effectively in disease states. Healthy volunteers between 18 and 45 years of age may be eligible for this study. Candidates will be screened with a medical history, physical examination, and blood and urine tests. Participants will undergo magnetic resonance imaging (MRI) and PET scanning as follows: PET SCAN: A catheter (plastic tube) is inserted into a blood vessel (radial artery) in the subject's wrist to collect blood samples during the procedure and in a vein in the opposite arm to inject radioactive tracers. The subject lies on the scanner bed, wearing a special facemask and goggles. The mask helps hold the head still during the scans, and the goggles either block all light or administer bright flashing lights at a frequency of about 8 times a second. Four injections of radioactive water are given about 15 minutes apart, and then, 15 minutes after the last injection, two injections of arachidonic acid are given, 60 minutes apart. The PET scanner detects the radioactive substances in the brain and shows brain blood flow and phospholipid metabolism in the different regions of the brain under the conditions of darkness and during visual stimulation. This provides information on how and where the brain responds to visual stimulation. The entire procedure takes about 3 hours. MRI: For this procedure, the subject lies on a table in a narrow cylinder (the scanner) containing a magnetic field. He or she wears earplugs to muffle loud noises caused by electrical switching of radio frequency circuits used in the scanning process and lies still for 15 to 30 minutes at a time. The results of the MRI are used to help analyze data on brain blood flow and fatty acid metabolism obtained from PET imaging. MRI uses a strong magnetic field and radio waves to shows structural and chemical changes in body tissues.
Details: A new method to quantify and localize brain signal transduction involving phospholipase A2 (PLA2) has been developed in awake rats and monkeys using quantitative autoradiography or positron emission tomography (PET), and radiolabeled arachidonic acid. In humans, however, no reliable in vivo imaging method exists to examine brain signal transduction in relation to physiological or pharmacological activation. PET has been used in humans to quantify regional cerebral glucose metabolism and blood flow, and to estimate regional densities of receptors, but has not been used successfully to examine ''signaling beyond the receptor." Functional magnetic resonance imaging (fMRI) has been used to quantify signals related to regional blood flow, and magnetic resonance spectroscopy has allowed measurements of brain metabolites. On the basis of studies in rats and rhesus monkey and of a PET study in young healthy volunteers we hypothesize that it should be possible to use the positron-emitting radiotracer [11C]arachidonate with PET to image and quantify PLA2-mediated signal transduction in the human being in response to pharmacological or physiological activation. Based on our prior measurements in human subjects of regional cerebral blood flow (rCBF) during visual activation by flashing lights at different frequencies (Mentis et al. 1997a), we hypothesize that statistically significant increments in [11C]arachidonate incorporation into the brain will be found using PET in human subjects during visual activation compared with the (unactivated) condition. These increments, we expect, will be evident in the primary visual cortex (Brodmann area 17), the association visual cortex (Brodmann areas 18 and 19), and the thalamus. If out hypothesis proves correct and our method to measure [11C]arachidonate incorporation during stimulation and in the dark proves feasible, we believe that the method could be applied generally in humans to examine brain PLA2-related signal transduction, during physiological or pharmacological activation and in health and disease.
Eligibility:
Study Type: Observational, Natural History
Minimum Age/Maximum Age: /
Genders: Both
Protocol Entry Criteria: INCLUSION CRITERIA Healthy volunteers will be recruited for this protocol. All subjects must have normal values on screening measures to be in the study. Age between 18 and 45 years. EXCLUSION CRITERIA Past or current medical condition that would interfere with brain function: history of alcoholism; psychiatric or neurological illness; head trauma with loss of consciousness; history of central nervous system infection; metabolic, endocrine, connective tissue disease; hypertension or other cardiovascular disorder; abnormal renal, liver or pulmonary function; blood or coagulation disease; malignancy; pharmacological treatment; neurodegenerative or neurodevelopmental disorder; stroke; epilepsy; sensitivity to flashing lights. Subjects requiring regular medication. Subjects demonstrated by drug screening to have taken controlled substance. For female subjects, pregnancy or current breast-feeding (nursing).
Total Enrollment: 30
Location and Contact Information:
National Institute of Neurological Disorders and Stroke (NINDS) *Recruiting*
Bethesda, Maryland, 20892
United States
Recruiting Giuseppe Esposito 3014021962
Additional Information:
Study ID Numbers: 000057; 00-N-0057
Study Start Date: January 10, 2000
Record last reviewed: July 2, 2003
Additional information available at: clinicaltrials.gov
Clinicaltrials.gov Reference link: NCT00044200
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2. PET Imaging of Dopamine in Healthy Study Participants
3. Immune Responses to HIV in Blood Cells in HIV-Infected and HIV-Uninfected Volunteers
4. Magnetic Stimulation of the Human Nervous System
5. Rimonabant to Reduce Alcohol Consumption
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Positron Emission Tomography (PET) to Study Brain Signaling
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