ABSTRACT
Several studies suggest that impaired cholinergic function plays an important role in the memory and cognitive deficits of normal aging. Numerous neurochemical studies performed on autopsy and biopsy samples of brain regions demonstrate a greater involvement of the cholinergic system in Alzheimer disease (AD). The presence of cholinergic dysfunction in a wide spectrum of CNS diseases has prompted many investigators to ask whether acetylcholine metabolism in brain is reflected by changes in cholinergic indexes that can be monitored through neural and extraneural markers. The existence of several subtypes of nicotinic cholinergic receptors in the brain would suggest specific anatomical localizations and functions. In situ hybridization techniques suggest the presence of three independent nicotinic receptor subtypes in the rat brain each showing specific kinetics, regional distribution and synaptic localization. Among several extraneuronal markers the presence of antibodies to cholinergic neurons, if confirmed, is of particular interest. In the future, new markers may be developed which might be more selective for presynaptic changes.
