Elevation of Plasma LH in Response to Systemic Injection of β-Endorphin Antiserum in Adult Male Rats

Abstract A single injection of β-endorphin antiserum into mature male rats produced approximately a 3-fold rise in plasma LH levels by 10 to 50 min, and declined by 90 min, but remained significantly elevated above pre-injection values. Control rats injected with normal rabbit serum showed no elevation in plasma LH values. These results indicate that β-endorphin is one of the endogenous opiates that tonically depresses basal release of LH in mature male rats.