M3Rezeptoren

The M3 receptor, also known as the muscarinic acetylcholine receptor M3 (CHRM3), is a subtype of muscarinic acetylcholine receptors (mAChRs) that belong to the family of G protein-coupled receptors (GPCRs). These receptors are widely distributed across various tissues and play a crucial role in mediating the effects of acetylcholine, a key neurotransmitter in the parasympathetic nervous system.

M3 receptors are particularly abundant in smooth muscle cells, glandular tissues, and certain regions of the central nervous system. They are coupled to Gq/11 proteins, which activate phospholipase C, leading to the production of inositol trisphosphate (IP3) and diacylglycerol (DAG). This signaling cascade increases intracellular calcium levels, triggering downstream effects such as muscle contraction and secretion.

In the cardiovascular system, M3 receptors influence vascular endothelial cells, contributing to vasodilation through the release of nitric oxide. They also regulate bronchial smooth muscle tone, making them significant in respiratory physiology. In the gastrointestinal tract, these receptors modulate peristalsis and secretion, while in the eye, they affect accommodation and pupil constriction.

Activation of M3 receptors is involved in various physiological processes, including salivation, lacrimation, and gastric acid secretion. Dysregulation or excessive stimulation of these receptors can lead to pathological conditions, such as bronchoconstriction in asthma or excessive gastrointestinal motility in irritable bowel syndrome.

Pharmacologically, M3 receptors are targeted by muscarinic agonists and antagonists. Muscarinic agonists, such as bethanechol, stimulate M3 receptors to treat urinary retention or gastrointestinal hypomotility. Conversely, muscarinic antagonists, including atropine and ipratropium, block these receptors to manage conditions like overactive bladder, asthma, or peptic ulcers. The selective modulation of M3 receptors remains an area of interest in drug development for therapeutic applications.