Opiate

An opium-like substance which regulates pain perception and pain signaling pathways and mood (see Fig. O16). Endogenous opiates, enkephalins and endorphins, were isolated from the brain and the pituitary gland, respectively. They contain a common 4-amino acid sequence and bind to the same cell surface receptors as morphine (and similar alkaloids). Nociceptins (orphanin) are 17 amino acid antagonists of the opioid receptor-like receptor. Opioids are opiate-like, but they are not derived from opium. Nocistatin with an evolutionarily conserved C-terminal hexapeptide blocks pain transmission in mammals. Opioids activate the expression of FAS which upon binding its ligand (FasL)