Ks. Lee et al., IN-VIVO QUANTIFICATION OF CEREBRAL MUSCARINIC RECEPTORS IN NORMAL HUMAN AGING USING POSITRON EMISSION TOMOGRAPHY AND [C-11] TROPANYL BENZILATE, Journal of cerebral blood flow and metabolism, 16(2), 1996, pp. 303-310
Regional cerebral muscarinic cholinergic receptor binding was quantifi
ed in normal young and elderly subjects employing the muscarinic antag
onist radioligand [C-11]tropanyl benzilate (TRB). Binding was determin
ed by kinetic analyses of positron emission tomographic (PET) determin
ations of cerebral activity in conjunction with radial arterial blood
sampling following intravenous radiotracer injection. A significant, b
ut minor (8%), loss of frontal cortical receptors relative to whole br
ain average receptor density was found with advancing age. Parametric
estimates of binding suggest small reductions in cerebral cortex bindi
ng as well as increases in brain stem and cerebellar binding underlyin
g the observed pattern difference. However, these latter changes did n
ot achieve statistical significance. We conclude that cerebral muscari
nic receptor availability, as depicted by antagonist binding, does not
undergo a major decline during normal aging of the adult human brain.
The cerebral cortical cholinergic dysfunction in elderly subjects, su
ggested by prior clinical evidence, is not attributable to major loss
of total muscarinic cholinoceptive capacity.