Role of Dopamine in Pleasure, Reward and Subjective Responses to Drugs

Abstract

This chapter will attempt to accomplish a seemingly impossible task of characterizing the concept of quality of life in terms of pleasure centres, neuronal circuits and chemical mechanisms in the brain. The supporting explanations will be presented in three parts: first, identifying three key characteristics of quality of life – first, the central doctrine of subjectivity, the time frame of appraisal, and the relevance of immediate affective tone in determining quality of life ratings; second, a review of the cumulative knowledge on the neuroanatomical and neurochemical mechanisms underlying subjective responses to pleasurable stimuli such as food and drugs. Thirdly, evidence is presented to support that interference with these brain reward mechanisms leads to feelings of lack of pleasure and poor quality of life, citing antipsychotic drug therapy in schizophrenia as an example. Laboratory experiments in animals and neurochemical imaging studies in humans suggest that dopaminergic mechanisms in nucleus accumbens, amygdala, hippocampus and prefrontal cortex are key players in determining the qualitative and quantitative aspects of subjective responses to pleasurable stimuli. Antipsychotic drug induced dopaminergic blockade in these neuronal circuits leads to persistent feelings of dysphoria and pervasive lack of pleasure, leading to subjective distress and compromised quality of life. The nuances of subjective responses to antipsychotic drugs thus have enormous implications for long term care of the mentally ill people