Release of beta-endorphin from rat hypothalamus in vitro

The rate of release of beta-endorphin-like immunoreactivity (beta-EI) from rat hypothalamic slices was increased 3- to 4-fold over the spontaneous release during exposure to a depolarizing concentration of potassium ions. This augmented outflow was abolished in the absence of calcium. The amount of beta-EI released from slices exposed to a second pulse of potassium was reduced by approximately 50% compared to that in the first. 70% of the potassium-induced released immunoreactive material migrated on a calibrated Sephadex G-50 column like synthetic human beta-endorphin. These findings are discussed in terms of a neuronal release of beta-endorphin and may be taken as supportive evidence for a neurotransmitter and/or neurohormonal role of beta-endorphin in the hypothalamus.