Proopiomelanocortin (POMC) is located inside the brain in the hypothalamus. This part of the brain is attributed to regulating hunger, thirst, sex drive and other pleasurable activities.
A recent study in mice seems to connect this region of the brain to how the brain and body handle stress. One of the interesting aspects of this study is how stimulation and lack of stimulation appears to affect mood, specifically "lack of pleasurable feelings".
This lack of experiencing pleasure can have a long term negative effect, called "depression", if not reversed. It may be common knowledge that these feelings are linked to a depressed mood and brought on by chronic stress (the focus of the study) and having the scientific insight helps people struggling with these feelings to both understand and seek new treatment.