Human Brain Imaging of Acetylcholine Receptors

The neurotransmitter acetylcholine (ACh) is widely distributed within the central nervous system (CNS) and is involved in a number of important processes, including roles in sensory and motor processing, sleep, nociception, mood, stress response, attention, arousal, memory, motivation, and reward. The actions of ACh are mediated through the muscarinic ACh receptor (mAChR) and nicotinic ACh receptor (nAChR). Postmortem studies indicated marked changes in the mAChR and nAChR in the brain associated with several neurological disorders. Selective radioligands have been developed for mapping these receptors using single photon emission computed tomography (SPECT) and positron emission tomography (PET). A number of clinical studies have identified the changes in ACh receptors (AChRs) in aging, neurodegenerative diseases, and many other types of neurological disorder. In addition, a number of clinical studies elucidated the mechanisms of action of pharmaceuticals and tobacco addiction. This chapter presents a summary of the research regarding the clinical brain imaging of AChRs by SPECT and PET, and discusses the potential usefulness of these techniques in the pathofunctional analysis of CNS diseases.