Neuropeptides in the median eminence

The presence and possible sources of more than 30 neuropeptides in the median eminence are summarized. The median eminence is the brain area which contains neuropeptides in the highest number and in the highest concentrations in the central nervous system. This area constitutes the final common pathway for signals from the brain to the pituitary. Many peptidergic fibers enter the median eminence and terminate around the pericapillary space and release their neuropeptides into hypophysial portal blood vessels. Other peptidergic fibers traverse the median eminence and terminate in the posterior pituitary. According to their origin, fibers in the median eminence can be classified as intra- or extrahypothalamic fibers. The neuropeptide-containing fibers in the median eminence are mainly intrahypothalamic, they reach the median eminence through either the lateral retrochiasmatic area or the tuberoinfundibular tract. Depending on the site of their action, neuropeptides may be either neurohormones acting on the anterior pituitary cells or neurotransmitters affecting the release of substances from other nerve terminals within the median eminence.