Volume transmission of beta-endorphin via the cerebrospinal fluid; a review.

There is increasing evidence that non-synaptic communication by volume transmission in the flowing CSF plays an important role in neural mechanisms, especially for extending the duration of behavioral effects. In the present review, we explore the mechanisms involved in the behavioral and physiological effects of beta-endorphin (beta-END), especially those involving the cerebrospinal fluid (CSF), as a message transport system to reach distant brain areas. The major source of beta-END are the pro-opio-melano-cortin (POMC) neurons, located in the arcuate hypothalamic nucleus (ARH), bordering the 3rd ventricle. In addition, numerous varicose beta-END-immunoreactive fibers are situated close to the ventricular surfaces. In the present paper we surveyed the evidence that volume transmission via the CSF can be considered as an option for messages to reach remote brain areas. Some of the points discussed in the present review are: release mechanisms of beta-END, independence of peripheral versus central levels, central beta-END migration over considerable distances, behavioral effects of beta-END depend on location of ventricular administration, and abundance of mu and delta opioid receptors in the periventricular regions of the brain.