Neurobiology and Psychopharmacology
Select two of the following neurotransmitters:
- Serotonin
- Norepinephrine
- Dopamine
- Acetylcholine
- Glutamate
- Melatonin
- Histamine
- GABA
For each neurotransmitter, please discuss the following: pharmacologic action, the drug class it is most closely linked to, expected outcomes, and potential side effects. Based on this information, which condition would these neurotransmitters be considered for the treatment plan?
Textbook:
Neurobiology, Brain Anatomy, Neurotransmitter Synthesis, and Function
Section 2 of 3
Neurotransmitters are related to how the brain functions and how one feels. The most common neurotransmitters related to mental health are serotonin, norepinephrine, dopamine, acetylcholine, glutamate, and GABA (γ-aminobutyric acid).
Different medications are either agonists, partial agonists, antagonists, or inverse agonists. The neurotransmitter is the agonist. The antagonists are the opposite and are considered neutral. They are the cause of many side effects associated with psychiatric medications. The agonist imitates the action of the intended chemical for that receptor, thus creating a comparable response. The antagonist does the very opposite and elicits no response.
A partial agonist is somewhere in the middle; it is more than an antagonist but less than a full agonist. An inverse agonist is a drug that binds to the same receptor as an agonist but induces a pharmacological response opposite to that of the agonist. A neutral antagonist has no activity in the absence of an agonist or inverse agonist but can block the activity of either. The clinical significance of this action when compared to an antagonist is questionable.
The cytochrome P450 enzyme system is responsible for metabolism of psychiatric medications. Click below to learn more.CYP1A2+
CYP2D6+
CYP3A4+
LIGAND-GATED ION CHANNELS
Psychiatric medications can target ligand-gated ion channels. Review the chart below:
| Neurotransmitter | Ligand-gated ion channel receptor subtype directly targeted | Pharmacologic action | Drug class | Therapeutic action |
|---|---|---|---|---|
| Acetylcholine | α4β2 nicotinic receptors | Partial agonist | Nicotinic receptor partial agonist (NRPA) (varenicline) | Smoking cessation |
| GABA | GABAA benzodiazepine receptors | Full agonist | Benzodiazepines | Anxiolytic |
| GABA | GABAA non-benzodiazepine PAM sites | Full agonist | “Z drugs”/hypnotics (zolpidem, zaleplon, zopiclone, eszopiclone) | Improve insomnia |
| Glutamate | NMDA NAM channel sites/Mg++ sites | Antagonist | NMDA glutamate antagonist (memantine) | Slowing progression in Alzheimer’s disease |
| Glutamate | NMDA open channel sites | Antagonist | PCP (phencyclidine), ketamine | Hallucinogen anesthetic |
| Serotonin | 5HT3 | Antagonist | Antidepressant (mirtazapine) | Unknown; reduce nausea |
| Serotonin | 5HT3 | Antagonist | Antiemetic | Reduce chemotherapy-induced emesis |
