According to the text, Acetylcholine (ACh) has been shown to enhance the uptake of radioactive glucose into C2C12 cells within a certain concentration range. It is believed that this effect is due to the activation of muscarinic M1 receptors. Additionally, inhibition of the enzyme phospholipase C by U73312 can also enhance glucose uptake. The use of an antagonist, pirenzepine, can potentially reduce the effects of ACh activation on glucose uptake. Activation of M1 or M4 receptors has been proposed to improve spatial memory and reduce symptoms of schizophrenia. However, the activation of M3 receptors has been shown to stimulate colon cancer cell growth, invasion, and migration. The presence of mEGFP may interfere with the activation of heterotrimeric G proteins by muscarinic agonists. Some M1 positive allosteric modulators (PAMs) have been found to have excessive activation of M1 receptors, leading to seizures and potential cognitive impairment.