Primary Mechanisms of Psychotropic Medication
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Psychotropic medications, also known as psychiatric medications, are used for managing a range of mental health disorders, from anxiety and depression to schizophrenia and ADHD. Today, we're taking a closer look at the most common mechanisms of these drugs, focusing on concepts such as agonists, antagonists, and their interactions with receptors and transporter proteins.
This post will lay the framework for future posts, which will examine the mechanism of specific classes of medications, such as stimulants, atypical antipsychotics, or selective serotonin reuptake inhibitors.
Introduction
Understanding psychotropic drugs might seem overwhelming with various classes, functions, and side effects. But it all boils down to the interactions of three basic entities in our brain - neurons, neurotransmitters, and receptors. This post aims to deconstruct these complex interactions and explain how psychotropic drugs work.
Neurons, Neurotransmitters, and Receptors
Neurons are the fundamental units of the brain, forming an intricate network that enables all our thoughts and behaviors. They communicate using chemicals called neurotransmitters, which travel across a small gap (the synapse) to reach neighboring neurons. Upon reaching the other side, these neurotransmitters bind to specific proteins, called receptors, on the receiving neuron, initiating various changes in the neuron's function.
Drug Actions: Agonists vs. Antagonists
Psychotropic drugs function as either agonists or antagonists:
Agonists are drugs that boost a neurotransmitter's action. They achieve this either by mimicking the neurotransmitter and binding to its receptors (direct agonists), stimulating an increased release of the neurotransmitter, or blocking the reuptake or breakdown of the neurotransmitter, thereby increasing its concentration.
Antagonists, conversely, diminish a neurotransmitter's action. They do this by blocking the receptor and preventing the neurotransmitter from binding and causing an effect (direct antagonists), or by reducing the neurotransmitter's release.
Acting on Receptors vs. Transporter Proteins
Psychotropic drugs primarily exert their influence through either receptors or transporter proteins:
Receptors: When neurotransmitters bind to these proteins, it causes a reaction in the neuron. Many psychotropic drugs work by either stimulating these receptors (an agonist effect) or blocking them (an antagonist effect).
Transporter Proteins: These proteins are in charge of reuptake - the process of transporting the neurotransmitter back into the neuron that released it, reducing its availability in the synapse. Some psychotropic drugs, like Selective Serotonin Reuptake Inhibitors (SSRIs) and ADHD stimulants, block these transporter proteins, thereby enhancing the concentration of the neurotransmitter in the synapse.
Additional Mechanisms of Action
Apart from acting as agonists or antagonists on receptors or transporter proteins, psychotropic drugs also influence neurotransmission in other ways:
Breakdown Inhibitors: These medications slow the degradation of neurotransmitters, thereby increasing their availability. For instance, Monoamine Oxidase Inhibitors (MAOIs) block an enzyme that breaks down neurotransmitters like serotonin and norepinephrine.
Presynaptic Autoreceptors: Autoreceptors are self-regulating feedback mechanisms for neurons. Drugs that act on these receptors can enhance or decrease neurotransmitter release. For instance, certain antipsychotic drugs block dopamine autoreceptors, leading to increased dopamine release.
Conclusion
The intricate interplay between neurons, neurotransmitters, and psychotropic medications underpins our understanding of these drugs' mechanisms of action. While these explanations might seem straightforward, the human brain's exact functioning is exceptionally complex and still a subject of ongoing research. Nonetheless, this understanding empowers us to appreciate the sophisticated choreography that enables us to think, feel, and perceive the world around us.
In a previous post, we discussed some of some of the most commonly acted upon receptors & transporter proteins in psychiatry. Understanding each will give you a leg up in understanding how medications exert their effect on the body. You can a review those HERE.