Foundational Neuroscience The Agonist-To-Antagonist Spectrum of Action of Psychopharmacologic Agents

Agonists are neurotransmitters that stimulate receptors while antagonists obstruct the action of neurotransmitters at its receptor. Drugs act in the same manner where some medications trigger receptors just like neurotransmitters and therefore such drugs are agonists. Other medications normally obstruct the action of neurotransmitter at its receptor and therefore such medications are known as antagonists (Stahl, 2013).  In addition, other medications act on the contrary to agonists and are known as inverse agonists. Therefore, psychopharmacologic agents acting at the receptor occur within a spectrum from a complete agonist to antagonist and then to inverse agonist (Zimmer, 2016) Foundational Neuroscience. The spectrum involves agonists that open the ion channel entirely, while antagonists maintain the resting state, and finally, the inverse agonists close the ion channel (Stahl, 2013).

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Stahl (2013) explains that there are various medications that bind to neurotransmitter sites to produce signal transduction effects; these medications are direct-acting agonists. In addition, antagonists work by blocking agonists’ action. Therefore, antagonists can only function where an agonist is there; this means that medications that are antagonists do not have an inherent activity when an agonist is absent. Therefore, the antagonist will obstruct everything within the agonist spectrum (Stahl, 2013).

Actions of G Couple Proteins and Ion Gated Channels

G couple proteins normally have receptors that have trans-membrane regions that have binding sites for neurotransmitters. This facilitates the targeting of exact psychotropic medications. When medications bind to the sites, this can result in various modifications of receptor actions as a result of imitating or obstructing, the neurotransmitter function occurring at the receptor (Johnson & Lovinger, 2016). Actions of such medications can, therefore, influence molecular events. Similarly, the medications can alter the expressed genes and hence the proteins synthesized and the amplified functions. On the other hand, ion gated channels are linked to the ionotropic receptor; the ionotropic receptors are used as sites where neurotransmitters bind and therefore these can be target sites for medications (Stahl, 2013).

The Role of Epigenetics in Pharmacologic Action

Epigenetics is a system that regulates the silencing or expression of genes (Stahl, 2013). The body cells consist of comparable but differentiated pair of genes that can be silenced or expressed. Therefore, neurotransmission, genes or even medications can influence the specific genes that will be expressed or suppressed. Epigenetic control can suppress or express genes by altering the structure of chromatin using chemicals like phosphorylation, drugs, methylation or neurotransmission (Stahl, 2013). Chemical processes like methylation or phosphorylation can be disrupted using drugs and this controls if the genes are epigenetically suppressed or expressed. For instance, chromatin alterations from drug actions have led to antidepressant responses that are associated with triggering genetic changes (Stefanska & David, 2015).

How the information may Impact Medication Prescription to Clients

Some classes of drugs are prepared to control epigenetic action and thus pharmacologic action of such drugs is broader. This is because some pharmacological agents require epigenetically function on diverse genes in on to ensure their efficacy in treating some conditions (Stefanska & David, 2015). For example, while medications with the epigenetic function may be effective in treating some types of diseases like diabetes, the approach of using epigenetics in drugs has been shown not to be effective in the treatment of mental health disorders like schizoaffective disorder, depression or schizophrenia. Therefore, this information may impact the prescription of medications to clients in that some conditions may require drugs with an epigenetic action, while other conditions may not.

References

Johnson K & Lovinger D. (2016). Presynaptic G Protein-Coupled Receptors: Gatekeepers of Addiction? Front Cell Neurosci. 10(264).

Stahl, S. M. (2013). Stahl’s essential psychopharmacology: Neuroscientific basis and practical applications (4th ed.). New York, NY, US: Cambridge University.