Appearance of beta-endorphin-like immunoreactivity in human ventricular cerebrospinal fluid upon analgesic electrical stimulation.

beta-Endorphin-like immunoreactivity in human ventricular cerebrospinal fluid was measured with a specific radioimmunoassay. The subjects were undergoing a surgical procedure for relief of chronic intractable pain. This procedure involved the focal stimulation of a medial thalamic site adjacent to the wall of the third ventricle. Samples were collected before and during the analgesic stimulation. No beta-endorphin-like immunoreactivity could be detected prior to stimulation, suggesting that baseline levels are below 25 fmol/ml of cerebrospinal fluid. Electrical stimulation led to substantial increases (13- to 20-fold) in immunoreactive material in every subject. These results suggest that beta-endorphin-like material can be released into the ventricular system and may contribute to the pain blockade that results from periventricular stimulation.