Binaltorphimine

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Binaltorphimine (BNI) is a chemical that selectively blocks the kappa-opioid receptor (KOR) in the nervous system. It was one of the first highly selective KOR antagonists discovered, along with norbinaltorphimine (nor-BNI). Researchers use BNI to study how KORs influence pain, stress, mood, and addictive behaviors. The molecule is large and complex (molecular formula C41H45N3O6, molar mass about 675.8 g/mol) and can produce long-lasting effects in experiments.