Does apolipoprotein E (Apo-E) genotype influence nicotinic receptor binding in Alzheimer's disease

We wished to determine the influence of the apolipoprotein E (Apo-E) genoty pe on the loss of high affinity nicotinic acetylcholine receptor (nAChR) bi nding in Alzheimer's disease (AD). The interaction between epsilon4 allele gene dose and cholinergic loss in AD remains controversial. We have demonst rated that nicotinic binding is significantly lost in AD. Tissue from the m idfrontal (MF) cortex of 7 subjects with no epsilon4 allele copies (epsilon -/epsilon-) (mean death age 75.1 +/- 10.4 years) was compared to MF cortex of 14 subjects heterozygous for the epsilon4 allele (epsilon4/epsilon-) (me an death age 81.4 +/- 7.3 years) and MF cortex of 10 subjects homozygous fo r the epsilon4 allele (epsilon4/epsilon4) (mean death age 79.6 +/- 5.0 year s). All subjects were autopsy confirmed AD (using NIA and CERAD criteria) a nd met NINCDS-ADRDA clinical criteria for probable or possible AD. Nicotine AChR binding was assayed using the high affinity nicotinic agonist H-3-epi batidine ([H-3]-Epi). Apo-E genotype was determined in blood samples or in post-mortem tissue. The mean age at death was not significantly different a mong the groups (p = 0.19). There was no difference in mean [H-3]-Epi total binding among the three groups (6.7 +/- 4.6, 6.1 +/- 2.4, and 6.0 +/- 1.0 fmol/mg protein for epsilon-/epsilon-, epsilon4/epsilon-, and epsilon4/epsi lon4 respectively. We conclude that the presence or absence of the Apo-E4 g enotype does not influence the loss of high affinity nAChR in AD.