The Journal of pharmacology and experimental therapeutics
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J. Pharmacol. Exp. Ther. · Jan 1988
Nalbuphine: an autoradiographic opioid receptor binding profile in the central nervous system of an agonist/antagonist analgesic.
Nalbuphine is a potent agonist/antagonist analgesic with a low side effect profile and low abuse potential. Previous studies have shown that nalbuphine produces predominantly agonist (analgesic) effects at kappa receptors and antagonist (morphine-reversal) effects at mu receptors in vivo. The present study was designed to localize the sites of nalbuphine binding to mu, delta and kappa opioid receptors in the central nervous system (CNS) using in vitro labeling light microscopic autoradiography. ⋯ The autoradiographic distribution of [3H]nalbuphine binding sites in the CNS corresponds well to the distribution of mu and kappa opioid receptors. In addition, CNS areas (deep layers of the cerebral cortex, laminae I and II of the spinal cord, substantia gelatinosa of the trigeminal nerve, periaqueductal gray and thalamic nuclei) that mediate analgesia contain high concentrations of [3H]nalbuphine binding sites. In summary, these data demonstrate that nalbuphine acts on mu and kappa opioid receptors and identify anatomical loci in the CNS in which nalbuphine may produce its actions.