From the Research
Muscarinic receptors are actually found in skeletal muscle, as evidenced by recent studies, which challenges the traditional view that they are absent in skeletal muscle. The presence of muscarinic receptors in skeletal muscle has been demonstrated in several studies, including a 2023 review that discusses the modern concepts of the functions of muscarinic cholinoreceptors in skeletal muscles 1. This review highlights the role of muscarinic receptors in the modulation of neuromuscular transmission, development, and morphological rearrangements of the synaptic apparatus.
The traditional view that muscarinic receptors are not found in skeletal muscle is based on the idea that skeletal muscle contains only nicotinic acetylcholine receptors at the neuromuscular junction. However, this view has been challenged by recent studies that have demonstrated the presence of muscarinic receptors in skeletal muscle. For example, a 1996 study found that muscarinic receptors are present in cultured skeletal muscle and are involved in the regulation of phosphoinositide metabolism and intracellular calcium levels 2.
The presence of muscarinic receptors in skeletal muscle has significant implications for our understanding of the regulation of skeletal muscle function. Muscarinic receptors are known to mediate slower, longer-lasting responses to acetylcholine, which could play a role in the regulation of skeletal muscle contraction and relaxation. The absence of muscarinic receptors in skeletal muscle was thought to ensure that voluntary muscle contractions occur quickly and directly in response to neural signals, without the slower second-messenger systems associated with muscarinic receptor activation. However, the presence of muscarinic receptors in skeletal muscle suggests that this may not be the case, and that muscarinic receptors may play a role in the regulation of skeletal muscle function.
Some studies have investigated the subtypes of muscarinic receptors present in skeletal muscle, including a 2012 overview of muscarinic receptor subtypes that highlights the complexity of muscarinic receptor function in the nervous system and other tissues 3. Other studies have investigated the role of muscarinic receptors in other tissues, such as smooth muscle and the central nervous system, including a 1997 study on the subtypes of muscarinic receptors in smooth muscle 4 and a 2018 study on the distribution of muscarinic receptor subtypes in the central nervous system 5.
In terms of the clinical implications of the presence of muscarinic receptors in skeletal muscle, it is possible that muscarinic receptors could be a target for the treatment of skeletal muscle disorders, such as muscular dystrophy or muscle weakness. Further research is needed to fully understand the role of muscarinic receptors in skeletal muscle and to explore their potential as a therapeutic target.
Key points to consider:
- Muscarinic receptors are present in skeletal muscle, as demonstrated by recent studies
- The presence of muscarinic receptors in skeletal muscle challenges the traditional view that they are absent in skeletal muscle
- Muscarinic receptors may play a role in the regulation of skeletal muscle function, including contraction and relaxation
- The clinical implications of the presence of muscarinic receptors in skeletal muscle are not yet fully understood and require further research.