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Exploring the Nervous System: How Muscarinic Receptors Change Your Heartbeat and Breathing
In the process of neurotransmission in our body, there are many key roles that play an extremely important role. One of them is Muscarinic acetylcholine receptors (mAChRs). This type of receptor is not only involved in the regulation of heartbeat and breathing, but also plays multiple roles in the autonomic nervous system. This article will take an in-depth look at the function of Muscarinic receptors, specifically how they affect the heart and respiratory system.
Basic knowledge of Muscarinic receptors
Muscarinic receptors are the primary receptors of acetylcholine and are found primarily in the parasympathetic nervous system, and in some cases the sympathetic nervous system is also involved. These receptors are G protein-coupled receptors that transmit messages to intracellular G proteins through seven transmembrane regions.
Muscarinic receptors are so named because they are more sensitive to maclin than to nicotine.
How Muscarinic receptors affect heartbeat
The M2 Muscarinic receptor operates mainly in the heart and plays a key role in slowing down the heartbeat. When the heart receives signals from the parasympathetic nervous system, the M2 receptors reduce the rate of depolarization of the heart, which causes the heart rate to decrease. When M2 receptors are inhibited, such as when taking drugs such as atropine, the heart rate increases.
The role of M2 receptors in the heart is not limited to heartbeat control, but also affects the contractility of the atrium and the conduction rate of the atrioventricular node.
The role of Muscarinic receptors in the respiratory system
The M3 Muscarinic receptor mainly exists in the smooth muscle of the respiratory tract. When this receptor is activated, it causes smooth muscle contraction, causing bronchoconstriction. This is essential for regulating airway tension and maintaining normal breathing.
However, M3 receptors also promote the synthesis of nitric oxide in vascular endothelial cells, which causes the relaxation of adjacent smooth muscles and thereby balances the tone of blood vessels.
Pharmacological applications of Muscarinic receptors
A variety of drugs target Muscarinic receptors for clinical application. For example, atropine, used to dilate pupils, and suspensa, used to treat motion sickness, both work by modulating M-type receptors. In addition, the U.S. FDA recently approved a new drug, KarXT, which is the first antipsychotic drug that works through a Muscarinic mechanism, showing its unique effects and different side effects compared to traditional antipsychotic drugs.
Receptor subtypes and their functions
Muscarinic receptors can be divided into five subtypes (M1-M5) based on their structure and signaling mechanism. M1, M3 and M5 receptors are mainly coupled to Gq proteins, while M2 and M4 receptors are coupled to Gi/o proteins. These different receptor subtypes determine their specific roles in different tissues and systems and their physiological significance.
M1 receptors are related to secretion and nerve signal transmission, while M4 receptors are associated with various regulatory functions in the central nervous system.
Conclusion
Muscarinic receptors play an integral role in regulating vital physiological processes such as heartbeat and breathing. An in-depth understanding of the functions of these receptors and their pharmacological applications will not only expand our understanding of the human nervous system, but may also open up new possibilities in future clinical treatments. Will such biological exploration lead us to rethink treatments for diseases related to the nervous system?
