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.
Iodine is a popular adulterant used by drug test thwarters forced to submit to urinalysis on short notice. While scientific studies have demonstrated that iodine destroys certain drug metabolites (e.g. morphine) on contact, it is less efficient (though still somewhat effective) at eliminating marijuana metabolites.