Nicotinic and muscarinic subtypes in the human brain: Changes with aging and dementia

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Abstract
Different effects of normal aging on muscarinic and nicotinic receptor subtypes were observed in postmortem brain tissue from different regions of the human brain. A significant decrease in Ml and M2 receptors was found in cerebral cortex, while the Ml and especially the M2 receptors increased with age in the thalamus. A similar pattern of changes was also observed when using (−)3H‐nicotine as ligandfor nicotinic receptors in the cortex and thalamus. No significant changes in nicotinic receptor binding were observed with age in the cortex or thalamus, when using 3H‐acetylcholine as ligand. Nicotinic and muscarinic receptors in the brain are not equally affected in dementia disorders. A marked loss of high affinity nicotinic receptors was observed in cortical tissue from patients with Alzheimer's disease and with multi‐infaret dementia (MID). The muscarinic receptors were (both Ml and M2) increased in Alzheimer cortical tissue while they were decreased in MID.