There are several different types of neurotransmitters released by different neurons, and we can speak in broad terms about the kinds of functions associated with different neurotransmitters (Table 1). Much of what psychologists know about the functions of neurotransmitters come from research on the effects of medications on treating psychological disorders.
Psychoactive drugs can act as agonists or antagonists for a given neurotransmitter system.
agonists and antagonists
Agonists are chemicals that mimic a neurotransmitter at the receptor site and, thus, strengthen its effects. An antagonist, on the other hand, blocks or impedes the normal activity of a neurotransmitter at the receptor. Agonists and antagonists represent drugs that are prescribed to correct the specific neurotransmitter imbalances underlying a person’s condition. For example, Parkinson’s disease, a progressive nervous system disorder, is associated with low levels of dopamine. Therefore, a common treatment strategy for Parkinson’s disease involves using dopamine agonists, which mimic the effects of dopamine by binding to dopamine receptors. The drug LSD is structurally very similar to serotonin, and it affects the same neurons and receptors as serotonin.
neurotransmitter activity
Neurotransmitter | Involved in | Potential Effect on Behavior |
---|---|---|
Acetylcholine | Muscle action, memory | Increased arousal, enhanced cognition |
Beta-endorphin | Pain, pleasure | Decreased anxiety, decreased tension |
Dopamine | Mood, sleep, learning | Increased pleasure, suppressed appetite |
Gamma-aminobutyric acid (GABA) | Brain function, sleep | Decreased anxiety, decreased tension |
Glutamate | Memory, learning | Increased learning, enhanced memory |
Norepinephrine | Heart, intestines, alertness | Increased arousal, suppressed appetite |
Serotonin | Mood, sleep | Modulated mood, suppressed appetite |
Certain symptoms of schizophrenia are associated with overactive dopamine neurotransmission. The antipsychotics used to treat these symptoms are antagonists for dopamine—they block dopamine’s effects by binding its receptors without activating them. Thus, they prevent dopamine released by one neuron from signaling information to adjacent neurons.
Psychotropic drugs are not instant solutions for people suffering from psychological disorders. Often, an individual must take a drug for several weeks before seeing improvement, and many psychoactive drugs have significant negative side effects. Furthermore, individuals vary dramatically in how they respond to a drug. To improve chances for success, it is not uncommon for people receiving pharmacotherapy to undergo psychological and/or behavioral therapies as well. Some research suggests that combining drug therapy with other forms of therapy tends to be more effective than any one treatment alone (March et al., 2007).