Reward pathway

The nucleus accumbens is part of the limbic system. It receives dopaminergic input through the mesolimbic system that originates from cell bodies in the ventral segmental area (A 10 cell group). This mesolimbic dopaminergic pathway is part of the reward pathways. Drugs of abuse (cocaine, amphetamine, opiates or nicotine) have been shown to increase the level of dopamine release in these neurons. 

Virtually all abused substances appear to activate the same brain reward pathway. 

While activation of the reward pathways explains the pleasurable sensations associated with acute substance use, chronic use of abused substances resulting in both addiction and withdrawal may be related to neuroadaptive effects occurring within the brain. 

O Virtually all abused substances appear to activate the same brain reward pathway. Key components of the reward pathway are the dopamine (DA) mesocorticolimbic system that projects from the ventral tegmental area (VTA) and the nucleus accumbens (NA) to the prefrontal cortex, the amygdala, and the olfactory tubercle (Figs. 33-3 and 33-4).5 Animal studies... 

Koob, G.F., Drugs of abuse anatomy, pharmacology and function of reward pathways, TIPS, 13,177,1992. 

These dopaminergic reward pathways are critical for normal survival, since they provide the pleasure drives for eating, drinking and reproduction. However, this system produces similar sensations of pleasure with alcohol, cocaine, heroin, nicotine,... 

Outline how the mesolimbic reward pathway is implicated in addiction. 

If these changes are also present in central dopaminergic reward pathways, it may be that the allele is linked to impaired perception of reward. It has been suggested that an inherited dopamine deficit could be overcome by nicotine, which stimulates dopamine release thereby restoring dopamine function to normal levels [17]. In this way the polymorphism could confer susceptibility to tobacco use. 

Kreek, M. J. and Koob, G. F. Drug dependence stress and dysregulation of brain reward pathways. Drug Alcohol Depend. 51 23-47,1998. 

Wise RA (1987) The role of reward pathways in the development of drug dependence. Pharmacol... 

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