muskarinik

Muscarinic refers to a class of receptors that are activated by the neurotransmitter acetylcholine. These receptors are found throughout the body, playing a crucial role in the autonomic nervous system, particularly in the parasympathetic division. There are five known subtypes of muscarinic receptors, M1 through M5, each with slightly different distributions and functions.

M1 receptors are primarily found in the brain and on gastric parietal cells. In the brain, they are involved in cognitive functions such as learning and memory. On parietal cells, they stimulate gastric acid secretion.

M2 receptors are predominantly located in the heart, where they slow heart rate and reduce the force of contraction. They are also found in smooth muscle and in the central nervous system.

M3 receptors are present in smooth muscle throughout the body, including the gastrointestinal tract, bladder, and airways, where they mediate contraction. They are also found in exocrine glands, promoting secretion, and on endothelial cells, where they cause vasodilation.

M4 and M5 receptors are largely found in the central nervous system and their precise roles are still being investigated, though they are thought to be involved in motor control and reward pathways.

Drugs that target muscarinic receptors, known as muscarinic antagonists or agonists, are used to treat a variety of conditions. For example, antagonists are used for conditions like overactive bladder or chronic obstructive pulmonary disease, while agonists can be used to treat glaucoma or dry mouth. The activation or blockade of these receptors can have significant physiological effects.