Endorphins in CSF of chronic pain patients, in relation to augmenting-reducing response in visual averaged evoked response.

In 45 consecutive patients with chronic pain, visual averaged evoked responses (VAER) and the levels of fraction 1 endorphins in CSF were investigated. Patients with an augmenter response in VAER, i.e. the maximum amplitude increases when stimulus intensity is increased, were found to have significantly lower levels of fraction 1 endorphins than patients with a reducer response, i.e. the maximum amplitude in VAER decreases when stimulus intensity is increased. The results indicate that the endorphins function as endogenous antinociceptive factors.