Chapter 14 - Reward and drugs of abuse

Abstract

This chapter focuses on drug addiction in terms of its pathological relationship with learning and memory systems. Both natural rewards and drugs of abuse appear to use the same systems within the brain to influence and reinforce behavior, and these systems are involved in learning and memory, particularly in connecting motivations and memories with behaviors. The chapter examines drug addiction in a manner based loosely on the stages of memory, namely, acquisition, consolidation, and storage/retrieval. It presents some of the important findings regarding drug reward and addiction as part of the stages of memory. Initially, learning about natural rewards and drugs of abuse utilizes the same pathways in the brain. However, repeated use of drugs produces changes in the brain, not normally found with repeated natural rewards, because of the ability of drugs to go directly to the brain and produce their pharmacological effects. In doing so, the drugs alter the functioning of a number of structures in the brain. These alterations include changes in gene and protein expression, morphological changes in the neurons, and changes in glutamatergic signaling. The process of drug addiction is similar to the stages of memory in many ways, like from acquisition to consolidation and finally retrieval. But in drug addiction, the changes induced by the drugs are detrimental to people in terms of their ability to resist future consumption of the drug. Chronic drug use exhibit several long-term changes: difficulty in examining consolidation, changes in gene and protein expression, decrease in glutamatergic tone, a potentiated increase in glutamate release following an acute cocaine injection, changes in proteins that regulate postsynaptic glutamate signaling, and structural changes in the neurons.