Like the M 1 and M 3 muscarinic receptor, M 5 receptors are coupled with G proteins of class Gq that upregulate phospholipase C and, therefore, inositol trisphosphate and intracellular calcium as a signaling pathway.
Radioactive iodine is a very effective type of treatment for cancer of the thyroid gland. Thyroid cells absorb iodine. The radioactive iodine from the drink or capsule is absorbed into your body and picked up by the thyroid cancer cells wherever they are. So it can kill the cancer cells even if they have spread.
Radioactive iodine (131-I) is a radioactive isotope that is administered orally, in a liquid or capsule form. The majority of radioactive iodine is taken up by your remaining thyroid cells, since the thyroid normally uses iodine to make thyroid hormone. Very small amounts of iodine may also be taken up transiently by cells in your stomach, salivary glands, and ovaries/testicles.