123I-5-IA-85380 SPECT imaging of nicotinic receptors in Alzheimer disease and mild cognitive impairment.
Postmortem binding studies have established that the concentration of alpha(4)beta(2)-nicotinic acetylcholine receptors (alpha(4)beta(2)-nAChR) is reduced in advanced Alzheimer disease (AD). However, the status of this receptor in mild or prodromal AD has remained the subject of controversy.


METHODS
We compared alpha(4)beta(2)-nAChR availability in 8 brain regions of living human subjects who had AD and mild cognitive impairment (MCI) with that in age-matched healthy control subjects by using the ligand (123)I-5-IA-85380 ((123)I-5-IA) and SPECT. All subjects (n = 32) were nonsmokers; they were administered (123)I-5-IA as a bolus plus a constant infusion and imaged 6-8 h later under equilibrium conditions. The effect of diagnosis on regional alpha(4)beta(2)-nAChR availability (regional brain activity/total parent concentration in plasma, proportional to the binding potential) was analyzed using multivariate analysis of covariance, controlling for the effects of age and sex.


RESULTS
Despite a significant overall effect of diagnostic group on mean alpha(4)beta(2)-nAChR availability, univariate analyses revealed no group differences for any brain region analyzed. An exploratory analysis of the relationship between regional alpha(4)beta(2)-nAChR availability and neuropsychologic variables yielded several plausible correlations. However, after Bonferroni adjustment, only the correlation between the anterior cingulate and the Trail Making Test, Part B, in the healthy control subjects remained significant.


CONCLUSIONS
These results are consistent with several postmortem and in vivo studies suggesting the preservation of nAChRs during the prodromal and early stages of AD. They support the interpretation that nAChR and other cholinergic reductions in AD are late-stage phenomena.
Mitsis
Effie M
EM
Alzheimer's Disease Research Unit, Yale University School of Medicine, New Haven, Connecticut, USA.
Reech
Kristina M
KM
Bois
Frederic
F
Tamagnan
Gilles D
GD
Macavoy
Martha G
MG
Seibyl
John P
JP
Staley
Julie K
JK
van Dyck
Christopher H
CH
D000368:Aged; D000544:Alzheimer Disease / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism*; D001384:Azetidines / Q000493:pharmacokinetics*; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism*; D003072:Cognition Disorders / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D011725:Pyridines / Q000493:pharmacokinetics*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D011978:Receptors, Nicotinic / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
C426745:5-iodo-3-(2-azetidinylmethoxy)pyridine; D001384:Azetidines; D011725:Pyridines; D019275:Radiopharmaceuticals; D011978:Receptors, Nicotinic