Explain the agonist-to-antagonist spectrum of action of
psychopharmacologic agents.
To understand the agonist-to-antagonist spectrum of action of
psychopharmacologic agents, it is first important to understand what do
...
Explain the agonist-to-antagonist spectrum of action of
psychopharmacologic agents.
To understand the agonist-to-antagonist spectrum of action of
psychopharmacologic agents, it is first important to understand what does the terms
agonist and antagonist means. An agonist refers to a chemical that binds to a receptor,
the receptor activates and a biological response is produced. In comparison, an
antagonist blocks the action of agonist, and an inverse agonist causes an action opposite
to that of the agonist (Stahl, 2013). The agonist spectrum can be classified into four
types namely agonist, partial agonist, antagonist and inverse agonist (Stahl, 2013). The
agonist opens the channel the maximal amount and frequency allowed by the binding
site, while antagonist that lie in the middle of the spectrum retain the resting state with
infrequent opening of the channel. The inverse agonist put the ion channel into a closed
and inactive state. Antagonists holds the ability to block anything in the agonist
spectrum, and ions are returned to their resting state in each instance (Stahl, 2013). An
agonist tie to a receptor site and causes a response while an antagonist works against
the drug and blocks the receptor. An agonist stimulates the action, while antagonist sit
idle, doing nothing (Stahl, 2013). For ideal therapeutic action of a drug, ion flow and
signal transduction is required that is not too hot, neither too cold and has the right
balance. Such an ideal state varies from one clinical case to another and depends upon
the balance between agonism and silent antagonism (Stahl, 2013).
Compare and contrast the actions of g couple proteins and ion
gated channels.
Two broad families of receptor proteins perform their functioning in the opening
and closing of postsynaptic ion channels. The receptor in one family is called the
ionotropic receptor is linked directly to ion channels. These receptors have two functional
domains, the first one being an extracellular site that binds neurotransmitters, and the
second one being a membrane-spanning domain to form an ion channel (Purves, et al.,
2012). Therefore, inotropic receptors combine transmitter-binding and channel functions
into one single molecular entity and are called ligand-gated ion channels. Such receptors
are multimers and are comprised to four or five individual proteins subunit. Each of these
units play a part in pore of the ion channel (Purves, et al., 2012).
The second family of neurotransmitter is the metabotropic receptor. In this case,
the movement of ion depends upon one or more metabolic steps. In these receptors,
there are no ion channels, but channels are affected by the activation of intermediate
molecules called G-proteins. For this same reason, metabotropic receptors are also
referred to as G-protein-coupled receptors (Purves, et al., 2012). Metabotropic receptors
are monomeric proteins having an extracellular domain for neurotransmitter binding and
an intracellular domain for binding to G-proteins. Neurotransmitter binding to
metabotropic receptors activates G-proteins, after which it dissociates from the receptor
and interact directly with ion channels or bind to other effector proteins, like enzymes to
make intracellular messengers to open or close ion channels. Therefore, G-proteins work
as transducers that couple neurotransmitter binding to the regulation of postsynaptic ion
channels (Purves, et al., 2012).
Explain the role of epigenetics in pharmacologic action.
Epigenetics is the study of changes that influence the phenotype without causing
changes in the genotype. It is the study on heritable but reversible changes in gene
expression without any modifications of primary DNA sequence (Lundstorm, 2015).
Epigenetic mechanisms, especially circulating miRNAs have greatly in use today for
diagnostic biomarkers (Lundstorm, 2015). Epigenetic regulation of gene activity is
important in maintain normal phenotypic activity of cells, as well as in treatment of
disease such as cancer and neurodegenerative disorders such as dementia and
schizophrenia. New classes of drugs are currently used to regulate epigenetic
mechanisms to manage diseases in individuals (Stefanska & MacEwan, 2015).
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