Psychoactive Drugs in AP Psychology

Heroin, naloxone, and cocaine at the synapse

Start with an overdose call. Someone has taken heroin, an opioid. Heroin works by fitting into the same receptors that endorphins, the body's natural painkillers, normally use. It mimics them and triggers the same response, which makes heroin an agonist. That explains the pain relief and the euphoria, and in an overdose it also explains the dangerously slowed breathing.

The paramedic then gives naloxone. Naloxone sits in those opioid receptors without activating them, which blocks heroin from acting. A drug that blocks a neurotransmitter's effect is an antagonist. It uses the same receptor as heroin but produces the opposite outcome.

Cocaine shows the third mechanism. Normally, after dopamine is released and does its job, the sending neuron pulls it back in. That step is called reuptake. Cocaine blocks that step, so dopamine builds up in the synapse and keeps stimulating the receiving neuron. That makes cocaine a reuptake inhibitor. SSRIs, a type of antidepressant, use the same mechanism on serotonin.

This is why psychoactive drugs sit in Unit 1: Biological Bases of Behavior, Topic 1.3: The Neuron and Neural Firing. The unit's argument is that behavior and mental processes run on biology, and drugs make that visible. Explaining any drug depends on the normal transmission sequence from 1.3.B, especially reuptake and the excitatory or inhibitory job of each neurotransmitter.

The four drug classes and the examples the course pairs with them

The course groups drugs by their typical overall effect, and it names an example for each:

• Stimulants, such as caffeine and cocaine, typically increase neural activity. Expect alertness, faster heart rate, and less fatigue.
• Depressants, such as alcohol, typically decrease neural activity. Expect slowed reactions, relaxation, and impaired judgment.
• Hallucinogens, such as marijuana, typically distort perception and/or cognition.
• Opioids, such as heroin, typically relieve pain.

The word "typically" matters. These are general patterns, and a single drug can have several effects. Every class also produces both psychological effects (mood, perception, thinking) and physiological ones (heart rate, breathing, coordination). If a question asks for one effect of each type, you can give both.

From first use to withdrawal: tolerance and addiction

With repeated use, the brain adjusts to a drug's constant presence. The result is tolerance, meaning the same dose produces a weaker effect, so a person needs more to get the original result. A daily coffee drinker who once felt wired from one cup and now needs three is showing tolerance.

Addiction is continued, compulsive use despite harm. When someone with an addiction stops taking the drug, they can go through significant withdrawal symptoms. Withdrawal often looks like the reverse of the drug's effect. Stopping caffeine can bring headaches and fatigue. Stopping heavy alcohol use can bring anxiety and tremors, and severe alcohol withdrawal can be medically dangerous.

Drug class and drug mechanism answer different questions

An answer that labels a drug an agonist because it's a stimulant, or an antagonist because it's a depressant, is mixing up two separate ideas. Class describes a drug's typical overall effects: more or less neural activity for stimulants and depressants, changes in perception or cognition for hallucinogens, and pain relief for opioids. Mechanism describes how the drug acts during neural communication, and one drug can act on more than one target. The two don't line up neatly.

Caffeine is a stimulant, but it blocks adenosine, a chemical that builds up during the day and promotes sleepiness. Blocking it is antagonist action, and the overall result is alertness. Heroin runs the other way. It's an agonist at opioid receptors, yet at high doses it slows breathing rather than speeding the body up.

Alcohol, a depressant, can enhance signaling by GABA, the main inhibitory neurotransmitter. Stronger inhibition means less neural firing, which helps explain alcohol's slowed reactions and relaxation. Before you pick a mechanism, figure out which neurotransmitter is involved and whether that neurotransmitter excites or inhibits.

A second mix-up concerns reuptake inhibitors. Because the word "inhibitor" is in the name, some answers say they reduce a neurotransmitter's effect. They do the opposite. Blocking reuptake leaves more of the neurotransmitter in the synapse.

Naming the mechanism in a scenario and reading drug studies

A stem that says a drug "binds to receptors and mimics acetylcholine" is pointing to an agonist. One that says a drug "prevents serotonin from being reabsorbed" is pointing to a reuptake inhibitor. Both standalone and set-based multiple-choice questions can describe a drug's action like this and ask you to name it. Other stems give you a person's symptoms and ask for the likely drug class, or describe someone needing larger doses and ask you to identify tolerance.

Drug research also fits the free-response formats. An Article Analysis summary could describe a drug study, and you'd identify the independent variable (the drug or placebo), the dependent variable (a measured behavior), and whether a double-blind procedure or placebo group was used. For part D, you'd pick one ethical guideline described in the summary, such as informed consent, and explain how the researchers applied it. On the Evidence-Based Question, a strong claim about a drug's effect cites specific findings from the sources and ties them to course knowledge, such as which neurotransmitter is involved and whether the drug acts as an agonist, antagonist, or reuptake inhibitor.