Final answer:
Psychoactive drugs alter an individual's chemistry by interacting with neurotransmitters in the brain, acting as either agonists or antagonists, leading to changes in mood, cognition, and behavior. Alcohol, a depressant, modifies the effects of GABA, an inhibitory neurotransmitter.
Step-by-step explanation:
The metabolic effects of alcohol and other drugs alter the individual's chemistry because psychoactive drugs mimic, displace, block or deplete neurotransmitters or their receptors.
Psychoactive drugs generally produce their effect by affecting brain chemistry. They can act either as agonists, which enhance the activity of particular neurotransmitters, or as antagonists, which decrease the activity of particular neurotransmitters. While they are used for various purposes such as medical, ritual, and recreational use, the misuse of psychoactive drugs may lead to addiction.
Alcohol, categorized as a depressant, is one example of a psychoactive drug that exerts its effects through mechanisms like facilitation of GABA (gamma-Aminobutyric acid), which is an inhibitory neurotransmitter in the central nervous system.