ABSTRACT
Advances in neurochemistry, including an understanding of the nature of neurotransmitter substances and their membrane receptors and the manner in which these receptors alter either ion channels or second messengers inside the cell, have provided the molecular basis for the action of many substances of abuse; yet there is no single molecular hypothesis that covers all addictions in a common understanding. In this chapter we will first provide some very simple definitions and then apply these definitions to describe the available information on the molecular basis of activity of abused substances. In the next chapter we will contrast the behavioral differences of alcohol and other abused substances.
