Neurotransmitters mediate the transmission of electrical impulses from one neuron to another. Multiple neurotransmitters are involved in central nervous system function, including amines (catecholamines, acetylcholine, and serotonin), amino acids (GABA, aspartate, and glutamate), peptides (neuropeptide Y), and gases such as nitric oxide (Sheffler et al., 2022). As discussed further, psychopharmacologic medications bind to specific neurotransmitter receptors, either activating (agonistic) or inhibiting (antagonistic).
Psychopharmacologic agents are useful in the treatment of a variety of psychiatric disorders, including mood disorders, trauma and stressor disorders, behavioral disorders, and psychotic disorders. The drugs exhibit either agonistic or antagonistic activity when acting at the receptor site. Whereas agonists bind to and activate a receptor to produce specific actions, antagonists bind to and block specific actions or responses (Katzung, 2018; Stern et al., 2015). The dopamine hypothesis, for example, is widely accepted in the etiology of schizophrenia.
Excessive dopaminergic transmission is thought to be responsible for schizophrenic symptoms, and research has found higher levels of dopaminergic receptors in schizophrenic patients (Stahl, 2018). This epiphany is why psychopharmacologic agents that block Dopamine receptors, such as chlorpromazine, are used to treat schizophrenia. In contrast, neurodegenerative disease such as Parkinson’s Disease (PD) has been linked to decreased dopamine levels and receptors, which is why dopamine agonists such as Levodopa are used to treat it.
Partial agonists bind to and activate receptors but have only partial efficacy. Partial agonists exhibit both agonistic and antagonistic actions, such as Buspirone, a partial agonist for 5HTA1 receptors and an antagonist for D2 receptors (Katzung, 2018). As a result, Buspirone can be used as both an anxiolytic and an antidepressant medication. Conversely, inverse agonists bind to receptors to produce effects opposite to those of the agonist (Katzung, 2018). Naltrexone is an example of a partial inverse agonist that is used to treat opioid addiction.
G-coupled proteins and Ion-gated chandelles are both cell surface receptors. To release ions, ligand-gated ion channels are controlled by neurotransmitters, whereas G-coupled receptors are entirely dependent on the second messenger system (Miller & Lappin, 2022). Because of the differences in stimulation mechanisms, the receptors take varying amounts of time to activate.
While ligand-gated ion channels are activated in milliseconds, G-coupled protein receptors take seconds (Miller & Lappin, 2022). Furthermore, nicotinic acetylcholine receptors and GABA A receptors are examples of ligand-gated ion channels, whereas G-coupled receptors include muscarinic acetylcholine receptors and adrenoceptors (Katzung, 2018; Miller & Lappin, 2020). Regardless of the differences, receptors are critical in carrying out physiologic functions at the molecular level.
Genes play an essential role in the body but so do the behaviors and environment. Epigenetics is the study of how behavior and environment influence gene expression (CDC, 2022). Unlike genetic changes, epigenetic changes are reversible and alter how the body reads the DNA sequence rather than changing the DNA sequence itself. The epigenetic changes may influence the pharmacology of certain drugs.
Brain-Derived Neurotrophic Factor (BDNF), for example, promotes neuronal survival and synaptic plasticity and is involved in learning, memory, and neurotransmitter release (Webb et al., 2020). BDNF is expressed differently across brain regions depending on environmental stressors, ushering in the concept of epigenetics. Human studies show that BDNF brain levels decrease in untreated major depressive illness and increase with antidepressant treatment (Webb et al., 2020). As a result, BDNF has emerged as a viable candidate for predicting response to antidepressant therapy.
Information regarding the pharmacology of drugs is critical in healthcare. In addition to understanding disease mechanisms, psychiatric mental health nurse practitioners (PMHNP) must be proficient in drug pharmacology knowledge. For example, in the etiology of PD, the PMHNP is aware of the link between the disease and Dopamine. As a result, a
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