M2reseptorit

M2reseptorit, also known as muscarinic acetylcholine receptor M2, are a type of G protein-coupled receptor found in the heart and other smooth muscles. They are part of the muscarinic acetylcholine receptor family, which are activated by the neurotransmitter acetylcholine. The M2 receptor is primarily associated with the inhibitory G protein (Gi), meaning that when activated, it leads to a decrease in cyclic AMP levels within the cell.

In the heart, M2 receptors are abundant in the sinoatrial node, atrioventricular node, and atrial muscle. Activation of M2 receptors by acetylcholine slows the heart rate (negative chronotropy), decreases the excitability of the atrioventricular node (negative dromotropy), and reduces the force of atrial contraction (negative inotropy). This effect is mediated by the parasympathetic nervous system, which releases acetylcholine to regulate heart function.

Beyond the heart, M2 receptors are also present in various smooth muscles, such as those in the bronchioles and gastrointestinal tract. Their activation in these tissues can lead to smooth muscle contraction. While M2 receptors play a significant role in regulating autonomic functions, their specific roles and distribution can vary depending on the tissue and species. Research continues to explore the intricate mechanisms and therapeutic potential associated with M2 receptor modulation.