Expression of the α3 nicotinic receptor subunit mRNA in aging and Alzheimer's disease

Changes in the number of high-affinity nicotine binding sites have been widely reported in specific regions of the human brain during aging and in degenerative neurological diseases associated with aging, such as Alzheimer's disease. Nicotinic receptors are highly diverse and a description of the molecular subtypes affected in such conditions has not been achieved to date. To investigate the status of the alpha 3 subunit-containing subtypes in such conditions, we assessed by in situ hybridisation the alpha 3 mRNA density in the hippocampus, entorhinal cortex and thalamus of Alzheimer's patients and age-matched controls. No significant difference in the expression of the alpha 3 mRNA, either qualitative or quantitative, was found between Alzheimer's individuals and controls in any of the analysed areas. This result suggests that the nicotine binding changes occurring in these areas in Alzheimer's patients are not correlated to a variation of the alpha 3 mRNA in the same regions; Nevertheless, a negative correlation between the alpha 3 mRNA density and the age was observed in the entorhinal cortex of both the Alzheimer's and the normal subjects, suggesting a potentially extensive decay of the alpha 3-expressing neurons or loss of alpha 3-containing receptors in intact neurons of the entorhinal cortex in the late elderly. (C) 1998 Elsevier Science B.V. All rights reserved.