Dopamine transporter PET in normal aging: dopamine transporter decline and its possible role in preservation of motor function.
OBJECTIVE
To determine the impact of age-related decline in dopamine transporter (DAT) expression on motor function in the elderly.


METHODS
About 33 normal individuals of a wide age range were scanned with PET employing d-threo-[(11)C]-methylphenidate (MP, a marker of DAT) and [(11)C]-dihydrotetrabenazine (DTBZ, that binds to the vesicular monoamine transporter Type 2). Motor function was assessed using the Purdue Pegboard Test (PPB). We analyzed the relationship between [(11)C]-MP and motor performance.


RESULTS
Age ranged from 27- to 77-year old (mean +/- SD, 54.75 +/- 14.14). There was no age-related decline in binding potentials (BP) for [(11)C]-DTBZ. In contrast, [(11)C]-MP BP was inversely related to age in all striatal regions analyzed (caudate: reduction of 11.2% per decade, P < 0.0001, r = -0.86; putamen: reduction of 10.5% per decade, P < 0.0001, r = -0.80). A differential effect of [(11)C]-MP on PPB could be observed according to age group. There was a positive relation between the PPB and [(11)C]-MP in young individuals (coefficient = 13.56), whereas in individuals greater than 57 years this relationship was negative (coefficient = -19.53, P = 0.031).


CONCLUSIONS
Our findings confirm prior observations of age-related DAT decline and suggest that this phenomenon is independent of changes in VMAT2. After the fifth decade of life, this reduction in DAT binding is associated with a motor performance comparable to mid-adult life. These findings imply that biochemical processes associated with healthy aging may offset the naturaldecline in motor function observed in the elderly.
Troiano
André R
AR
Pacific Parkinson's Research Centre, University of British Columbia, Vancouver, British Columbia, Canada. andretroiano@gmail.com
Schulzer
Michael
M
de la Fuente-Fernandez
Raul
R
Mak
Edwin
E
McKenzie
Jess
J
Sossi
Vesna
V
McCormick
Siobhan
S
Ruth
Thomas J
TJ
Stoessl
A Jon
AJ
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001921:Brain / Q000000981:diagnostic imaging* / Q000502:physiology*; D002250:Carbon Radioisotopes; D002421:Caudate Nucleus / Q000000981:diagnostic imaging / Q000502:physiology; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008774:Methylphenidate; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009483:Neuropsychological Tests; D049268:Positron-Emission Tomography; D011699:Putamen / Q000000981:diagnostic imaging / Q000502:physiology; D013747:Tetrabenazine / Q000031:analogs & derivatives
D002250:Carbon Radioisotopes; D050483:Dopamine Plasma Membrane Transport Proteins; D008774:Methylphenidate; C032811:dihydrotetrabenazine; D013747:Tetrabenazine