Chapter 36 Positron emission tomography and cholinergic mechanisms: an overview

Abstract

This chapter provides an overview of positron emission tomography (PET) and cholinergic mechanisms. The mechanisms involved in neurotransmission are mainly because of the technical revolutions that have arisen, in the neuroscience field, in the past decade. The availability of high affinity cholinergic ligands radiolabeled at high specific activity has made it possible to study the cholinergic system, in a noninvasive way, in the brain and in the heart of animals and humans, using PET. The nicotine cerebral kinetics is studied in the brain of living baboons, using [ 11 C] nicotine. The feasibility of studing the heart and brain muscarinic receptors is described in humans and baboons, using [ 11 C] MQNB and [ 11 C] QNB respectively. High affinity, saturability, specificity, and stereospecificity of the binding of the radiotracers are shown in vivo with PET. Increases of muscarinic receptors are found in hypothyroidic patients and transient alterations of muscarinic receptors are seen in subjects with tachycardia induced by exercise. A nonequilibrium nonlinear model with identification of six parameters is presented for noninvasive quantification of muscarinic cholinergic receptors in vivo in dog hearts, using PET and [ 11 C] MQNB.