Opioids
The group of opioids includes morphine, heroin and cup-owned, so-called opioid peptides (enkephalins, endorphins, dynorfins, endomorphines and nociceptin). Opioids attach themselves to the special so-called opioid receptors on the cell surface and exert their action with the help of so-called g-proteins. There are three types of opioid receptors: delta, kappa and mu receptors.