Volume transmission of beta-endorphin via the cerebrospinal fluid; a review
1 Department of Anatomy (109), University Medical Center St. Radboud, PO Box 9101, 6500, HB, Nijmegen, the Netherlands
2 Department of Psychopharmacology, UIPS, University of Utrecht, Utrecht, the Netherlands
3 Department of Neuroscience, section Anatomy, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
4 Faculty of Science, Radboud University, Nijmegen, the Netherlands
Fluids and Barriers of the CNS 2012, 9:16 doi:10.1186/2045-8118-9-16Published: 10 August 2012
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 β-endorphin (β-END), especially those involving the cerebrospinal fluid (CSF), as a message transport system to reach distant brain areas. The major source of β-END are the pro-opio-melano-cortin (POMC) neurons, located in the arcuate hypothalamic nucleus (ARH), bordering the 3rd ventricle. In addition, numerous varicose β-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 β-END, independence of peripheral versus central levels, central β-END migration over considerable distances, behavioral effects of β-END depend on location of ventricular administration, and abundance of mu and delta opioid receptors in the periventricular regions of the brain.