Final answer:
Pharmacodynamics is the study of how drugs produce their effects, particularly focusing on psychoactive drugs that act as agonists or antagonists influencing brain chemistry.
Step-by-step explanation:
The subsection of pharmacology that studies how drugs produce their effects is known as pharmacodynamics. This branch focuses on the mechanisms of action by which psychoactive drugs influence brain chemistry, resulting in changes to mood, thinking, perception, and behavior.
Drugs can either act as agonists, enhancing the activity of neurotransmitters, or as antagonists, which inhibit neurotransmitter function. Psychoactive drugs can be used for medicinal purposes but also have the potential for abuse, leading to addiction and the need for rehabilitation. Understanding the interaction between drugs and the body's chemistry is crucial for the development of new medications and treatment strategies.