text: Enkephalin is also considered a neuropeptide, which in the human body performs as an important signaling molecule in the brain. Enkephalins are found in high concentration in the brain as well as in the cells of adrenal medulla. In response to pain, norepinephrine, a hormone that is activated in fight-or-flight response, is released along with endorphins. A 2017 study indicates that this polypeptide may be linked to brain functioning during the stress response, especially in the hippocampus and prefrontal cortex. This research has suggested that, as part of the stress response, several met-enkephalin analogs have increased activity in the hippocampus, while leu-enkephalin analogs as well as somatostatins are downregulated during stress. Stressors may impact neuropeptides whose action is localized to a specific brain region.