Disuccion 1:The agonist-to-antagonist spectrum of action of psychopharmacologic agents
It is important to understand the agonist to antagonist spectrum when considering medication therapy. An
agonist is a substance or drug that mimics the effects of neurotransmitters resulting in the same conformations
and biological responses of that neurotransmitter (Berg & Clarke, 2018). For instance, the medication albuterol
is an agonist, which mimics the effects of adrenaline by stimulating the beta 2 receptor to produce the effects of
adrenaline such as bronchial dilation. There are also different types of agonists based on their level of
response. Full agonists bind to receptors and produce the maximum response. Partial agonists bind to
receptors and activate the receptors but only produce a partial response. On the other hand, an antagonist
binds to a receptor and blocks an agonist from binding to the receptor and producing a response. Therefore,
the antagonist results in no changes.
Compare and contrast the actions of g couple proteins and ion gated channels
In order to adequately compare and contrast the actions of g-couple proteins and ion-gated-channels, we must
understand signal transduction cascades. A Signal transduction cascade is a series of chemical and electrical
events that occurs after a neuron has been activated. G-protein linked systems and ion channel systems are
two types of signal transduction cascades that occur in the brain. Therefore, medications to treat psychiatric
disorders target these two cascades in hope of improving a patient’s mental health. There are two main
neuroreceptors in the brain-inotropic and metabotropic receptors. G-coupled proteins are metabotropic
receptors that are “coupled” to second-messengers systems by G-proteins while inotropic or ligand-gated ion
channels perform conformational changes to open the channel like a door and allow ions such as NA and CA
to flow once a neurotransmitter binds to the receptor (Weir, 2020). Each system is triggered by
neurotransmitters that are housed inside vesicles within the neuron. However, the results are the same for both
signal transduction cascades—gene expression.
In, the case of the G-protein linked system the second messenger is a chemical while in an ion channel system
the second messenger is an enzyme. In the G-protein system, a neurotransmitter or first messenger binds to a
receptor on the g-protein in the postsynaptic membrane and changes its shape so it can attach to the G-protein
(Berg & Clarke, 2018). The g-protein is then able to bind to the enzyme so that the second messenger cAMP
can be activated and released. Second messengers then continue to activate the third and fourth messengers
by phosphorylation (Weir, 2020). This occurs when G-protein linked receptors activate the protein kinase A,
which attaches a phosphate group on Cred inside the cell nucleus and activates the transcription factor
causing the gene that is nearby to be activated (Stahl, 2013). DNA is then transcribed into RNA by RNA
polymerase, the enzyme that must be activated in order to transcribe DNA into RNA in the regulatory area of
the gene resulting in the ultimate goal– gene expression (Stahl, 2013).
In ion gated channels, the first messenger neurotransmitter depolarizes the cell by allowing sodium to rush into
the cell through ion channels on the membrane. This results in calcium rushing out and entering inside the
neuron (2nd messenger) resulting in the activation of a third messenger that removes a phosphate group and
reverses the actions of the third messenger which is typically the enzyme phosphatase (Stahl, 2013).
Phosphatase removes the phosphates of the phosphoproteins in ion channels. The protein calmodulin
interacts with the calcium that is present and activates calcium/calmodulin-dependent protein kinases and not a
phosphatase (Stahl, 2013). The kinase travels to the cell nucleus and adds a phosphate group to the CREB
thus activating the transcription factor and trigger gene expression like in the case of the G-protein system.
Both the G-protein system and the ion-channel system can either work together to activate CREB or against
one another.
The role of epigenetics in the pharmacologic action
What role does epigenetics play in the effectiveness of medication? Interestingly, the human genome contains
roughly 30,000 genes inside 3 billion DNA base pairs (Stahl, 2013). Epigenetics refers to the changes that
result from activation “on” or deactivation “off” of genes. Genes are activated by neurotransmission in the signal
transduction cascades. Epigenetics does not cause a change in the DNA sequence but instead, it changes the
structure of the chromatin which is inside a cell’s nucleus and determines the function of a cell (Stahl, 2013).
Therefore, epigenetics determines if a particular gene is expressed or silenced by blocking off transcription
factors via chemical modifications (Stahl, 2013). This can result in psychiatric disorders and affect the
effectiveness of psychopharmacological medications.
How this information may impact the way you prescribe medications to clients
Knowledge of the signal transduction cascade and epigenetics is important when selecting medication therapy.
How can a clinician prescribe a medication without the knowledge of how that medication will
pharmacologically work in the body? For instance, selective serotonin reuptake inhibitors (SSRI) are commonly
prescribed in the psychiatric population to treat patients with depression (NHS, n.d.). SSRIs are usually the
treatment of choice for patients who have constant depression and are first-line therapies because of their
limited side effects (NHS, n.d.) SSRI’s blocks the reuptake of the neurotransmitter serotonin by nerve cells.
This has an impact on patients’ mood, sleep, and emotions. The hope is that the increased Serotonin levels will
improve the patient’s depression. However, clinicians must be aware that it takes approximately two to four
weeks and sometimes even longer to witness the effects of the medication.
References
Berg, K. A., & Clarke, W. P. (2018). Making sense of pharmacology: Inverse agonism and functional selectivity.
The international journal of Neuropsychopharmacology, 21(10), 962–977. https://doi.org/10.1093/ijnp/pyy071
NHS. (n.d.). Selective serotonin reuptake inhibitors (SSRIs). https://www.nhs.uk/conditions/ssriantidepressants/
Stahl, S. M. (2013). Stahl’s essential psychopharmacology: Neuroscientific basis and practical applications (4th
ed.). New York, NY: Cambridge University Press
Weir, J. C. (2020). Ion channels, receptors, agonists, and antagonists.
https://www.anaesthesiajournal.co.uk/article/S1472-0299(19)30264-4/pdf
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Discussion 2 post: Explain the agonist-to-antagonist spectrum of action of psychopharmacologic agents,
including how partial and inverse agonist functionality may impact the efficacy of psychopharmacologic
treatments.
A review of what an agonist and antagonist are defined as, better led the direction of this post. An agonist is a
substance that binds to a receptor and triggers a response in the cell, increasing activity (Rosenthal &
Burchum, 2021). An antagonist opens the channel to the highest number and frequency allowed by the binding
site. A partial agonist activates a receptor but does not cause as much of a physiological change that a full
agonist does. An antagonist is a term that refers to a chemical substance that decreases or blocks the effects
of a neurotransmitter (Rosenthal & Burchum, 2021). An antagonist results in a resting state because ion
channels are in a closed and inactive state (Rosenthal & Burchum, 2021). On the other hand, an inverse
agonist binds to the receptor site and does the opposite of an agonist. The optimal therapeutic activity includes
an ion flow and signal transduction that is not too subdued and not overly excited but balanced out for optimal
treatment of symptoms.
Compare and contrast the actions of g couple proteins and ion gated channels.
Two families of receptor proteins act in the opening and closure of post-synaptic ion channels. One receptor is
called the ionotropic receptor and the other is called the metabotropic receptor. Ionotropic receptors closely
connected to the ion channels. Both ionotropic and metabotropic receptors have two functionals, first being an
extracellular site that binds neurotransmitters, and the second, a membrane-widening region that forms an ion
channel. These receptors are multimers and consist of four to five individual protein subunits. Each of these
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units plays a part in the pore of the ion channel. Ionotropic receptors have a rapid result in calcium and
potassium exchange. Ionotropic receptors also act directly through ligand-gated ion channels and are usually
stimulated by neurotransmitters. Ionotropic receptors are mostly located postsynaptic. On the other hand,
metabotropic receptors act slower than ionotropic receptors. The signal is passed indirectly through g-protein
second messengers. Because the ion movement depends on metabolic steps, (as there is no ion channel in
the receptor) second messenger relay take time to receive the signal to detach and result in action.
Metabotropic neurons are either presynaptic or postsynaptic and are stimulated my neuromodulators.
Metabotropic receptors rely directly on g-proteins for their action. G-proteins are activated by a
neurotransmitter bound to metabotropic receptors. Once the ion attaches to the metabotropic receptor, the gprotein dissociates and interacts directly with ion channels or binds to other effector proteins. G-proteins act as
transducers that attach a couple of neurotransmitters to the modulation of post-synaptic ion channels. There
are three types of g-proteins that release from a metabotropic ion when the message is received, alpha, beta,
and gamma.
Explain how the role of epigenetics may contribute to pharmacologic action.
I want to first, define epigenetics as the study of changes that influence the phenotype without causing
genotype changes (McCance et al., 2019). It is a study of hereditary but reversible gene expression changes
without any alteration of the primary DNA sequence (McCance et al., 2019). The major mechanisms that are
involved in epigenetics regulation and the control of chromatin structure include DNA methylation,
posttranslational modification of histones, noncoding RNA, and nucleosome positioning (Sharma, 2019).
Epigenetic regulation of gene activity is essential for the maintenance of normal cell activity and the treatment
of diseases.
Explain how this information may impact the way you prescribe medications to patients. Include a specific
example of a situation or case with a patient in which the psychiatric mental health nurse practitioner must be
aware of the medication’s action.
When prescribing a medication, a provider must ensure that one is aware of different medication concepts that
will help offer the best quality of life (Brechin et al., 2020). As a nurse practitioner, it is important to inform the
patient of the possible side effects of the medication process. Side effects are one of the leading causes of
medication noncompliance (Rosenthal & Burchum, 2021). Through my experience as a psychiatric nurse,
several patients have been prescribed lithium. Through research and studies, I have discovered why Motrin is
always discontinued with our pediatric patients taking lithium. According to Rosenthal and Burchum (2021),
taking Motrin and lithium together may increase the levels of lithium in the body by decreasing the removal of
lithium by the kidneys, resulting in increased plasma lithium concentrations known at lithium toxicity. One must
understand the process of each medication that their patients are taking. Prescribing lithium to a patient
diagnosed with arthritis, could lead to a potentially fatal situation. It is essential to know the process of the
medications while educating patients accordingly.
References
Brechin, D., Codner, J., James, I. A., & Murphy, G. (2020). Alternatives to antipsychotic medication:
psychological approaches in managing psychological and behavioral distress in people with dementia.
McCance, K. L., Huether, S. E., Brashers, V. L., & Rote, N. S. (2019). Pathophysiology: the biologic basis for
disease in adults and children. Elsevier.
Rosenthal, L. D., & Burchum, J. R. (2021). Lehne’s pharmacotherapeutics for advanced practice nurses and
