Fig 1 β Endorphin levels in culture supernatants of mouse pituitary cells exposed to CRF and melatonin ( n=6).

Studies in rodents have shown that exogenous melatonin has beneficial effects on nociception, hyperalgesia, and allodynia in a variety of different pain models, including inflammatory pain studies, and independently of the route of its administration.The mechanisms remain unclear. Endorphins are endogenous peptides with opioid-like effects, and we hypothesised that melatonin may augment endorphin production.We determined the effect of melatonin on the release of β endorphin by pituitary and macrophage cell lines in vitro under inflammatory conditions.