The effects of age on dopamine receptors measured by positron tomography in the living human brain
C-11 n-methylspiperone has been used to measure dopamine (D2) receptors in the caudate and putamen of 30 normal persons. In vitro studies in rodent brain revealed a high affinity for dopamine (D2) receptors and five fold less for serotonin (S2) receptors. In vivo drug competition studies in rodents demonstrated that 90% of striatal binding is to dopamine receptors. In the frontal cortex, the majority of receptor binding is to serotonin receptors. Thirty normal volunteers aged 19 to 73 years were screened for normality by medical, neurological and neuropsychological examinations. Positron tomography was performed serially for 2 hours after injection. In 10 subjects there was good agreement between activity in arterial samples and that in venous samples from a heated hand. Binding in the dopamine rich caudate and putamen progressively increased while binding in the dopamine poor cerebellum decreased. The dopamine receptor density was estimated by the ratio of the caudate-to-cerebellar mean counts/pixel (Ca/Cb) and putamen-to-cerebellar mean counts/pixel (Pu/Cb). The ratios (Ca/Cb, Pu/Cb) increased linearly with time (r>0.95) for each subject. There was a decrease (Ca/Cb) with age (0.8%/yr) that could be approximated with a linear fit: (Ca/Cb = -.02 age + 3.92, r=.6). For the 21 males alone, the decrease was (1.1%/yr, r=.7 , p <.01), while for the 9 females there was no significant decrease with age. Similar findings were noted in the putamen. This decline in dopamine receptor density with age has been reported in rodent and human autopsy studies, but never before in the living human brain.
- Research Organization:
- The Johns Hopkins Medical Institutions, Baltimore, MD
- OSTI ID:
- 6930003
- Report Number(s):
- CONF-840619-
- Journal Information:
- J. Nucl. Med.; (United States), Journal Name: J. Nucl. Med.; (United States) Vol. 25:5; ISSN JNMEA
- Country of Publication:
- United States
- Language:
- English
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550602* -- Medicine-- External Radiation in Diagnostics-- (1980-)
62 RADIOLOGY AND NUCLEAR MEDICINE
AFFINITY
AGE DEPENDENCE
ALKYL RADICALS
AMINES
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BODY
BRAIN
CARBON 11
CARBON ISOTOPES
CARDIOTONICS
CARDIOVASCULAR AGENTS
CENTRAL NERVOUS SYSTEM
CEREBELLUM
CEREBRAL CORTEX
CEREBRUM
COMPUTERIZED TOMOGRAPHY
DENSITY
DIAGNOSTIC TECHNIQUES
DIAGNOSTIC USES
DOPAMINE
DRUGS
EMISSION COMPUTED TOMOGRAPHY
EVEN-ODD NUCLEI
FEMALES
HUMAN POPULATIONS
HYDROXY COMPOUNDS
IMAGE PROCESSING
IMAGES
IN VITRO
IN VIVO
ISOTOPES
LIGHT NUCLEI
MALES
MEMBRANE PROTEINS
METHYL RADICALS
MINUTES LIVING RADIOISOTOPES
NERVOUS SYSTEM
NEUROREGULATORS
NUCLEI
ORGANIC COMPOUNDS
ORGANS
PHENOLS
PHYSICAL PROPERTIES
POLYPHENOLS
POPULATIONS
POSITRON COMPUTED TOMOGRAPHY
PROCESSING
PROTEINS
RADICALS
RADIOISOTOPES
RECEPTORS
SYMPATHOMIMETICS
TOMOGRAPHY
USES