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Drug Addiction and Reward Circuits in the Brain

Presents the principles of drug action, and biological mechanisms involved in addiction to commonly abused psychoactive drugs.

1. Discuss the mechanisms of psychoactive drug action.
2. Identify the health hazards of commonly abused psychoactive drugs.
3. Explain the weight gain following smoking cessation.

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RESPONSE:

1. Discuss the mechanisms of psychoactive drug action.

Mechanisms of Psychoactive Drug Action - To produce psychoactive effects, drugs must enter the nervous system. It is fortunate, however, many drugs that are potentially dangerous neurotoxins do not readily penetrate the neurons of the CNS due to the blood-brain barrier. The particularly small pores in the walls of CNS blood vessels mediate it. Once a psychoactive drug has penetrated the CNS, however, it can influence neural activity in numerous ways; e.g., it can act diffusely on neural membranes or interact specifically with particular classes of neurotransmitters and receptors. The effects of psychoactive drugs are terminated by their metabolism, i.e., by their conversion to non-active metabolites; most drugs are metabolized by liver enzymes; only small amounts of un-metabolized active drugs are eliminated in sweat, breath, urine, etc. (1)

"Although many complex factors may be involved in excessive behaviors such as compulsive drug abuse, overeating, and gambling, they are all similar in that the brain is changed, reward circuits are disrupted, and the behavior eventually becomes involuntary," says Dr. Joseph Frascella of NIDA's Division of Treatment Research and Development. "Finding low D2 receptors across various drugs of abuse and now obesity ...

Solution Summary

Presents the principles of drug action, and biological mechanisms involved in addiction to commonly abused psychoactive drugs e.g. the mechanisms of psychoactive drug action, the health hazards of commonly abused psychoactive drugs and the weight gain following smoking cessation.

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