Release of immunoreactive beta-endorphin from synaptosome-enriched fraction of rat hypothalami.

Immunoreactive beta-endorphin is localized mainly in the synaptosome-enriched subcellular fraction from rat hypothalami. In this report, we demonstrate that release of immunoreactive beta-endorphin from the synaptosome-enriched subcellular fraction is increased by 150% in a medium containing high potassium. This stimulatory effect was dependent on temperature and calcium ion in the medium. These results suggest that hypothalamic beta-endorphin can be released from nerve endings during membrane depolarization processes.