Used in biomedical research to measure beta-endorphin (β-EP) levels in rat biological samples such as plasma, serum, or tissue homogenates. This immunoassay kit enables researchers to study the activity of the endogenous opioid system in rats, particularly in experiments related to stress, pain, addiction, and neuroendocrine function. It provides a sensitive and specific method for quantifying β-endorphin concentration, supporting investigations in pharmacology, neuroscience, and physiology. The kit is intended for research use only and not for diagnostic purposes in humans.