nalbuphine and Glioma

Opioid agonists acting at their receptors alter intracellular events by initiating activation of various types of Gi/Go proteins. This can be measured by the binding of the stable GTP analog [(35)S]guanosine-5'-O-(3-thio)triphosphate ([(35)S]GTPgammaS). In this study agonist efficacy is defined by the degree to which an opioid stimulates the binding of [(35)S]GTPgammaS. This allows for a definition of full and partial agonists; a full agonist causing a greater stimulation of [(35)S]GTPgammaS binding than a partial agonist. The hypothesis that the rate of agonist-stimulated [(35)S]GTPgammaS binding is dependent upon agonist efficacy was tested using membranes from C6 glioma cells expressing mu- or delta-opioid receptors. At maximal concentrations the rate of agonist-stimulated [(35)S]GTPgammaS binding followed the efficacy of mu-agonists in stimulating [(35)S]GTPgammaS binding, i.e., [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin > morphine > meperidine > butorphanol > nalbuphine. At submaximal concentrations of mu- or delta-full agonists the [(35)S]GTPgammaS association rate was also reduced, such that the rate of [(35)S]GTPgammaS binding correlated with the extent of [(35)S]GTPgammaS bound, whether this binding was stimulated by a full agonist or a partial agonist. Agonists also stimulated [(35)S]GTPgammaS dissociation, showing that binding of this stable nucleotide was reversible. Comparison of the delta-agonists [D-Ser(2),Leu(5)]-enkephalin-Thr and (+/-)-4-((alpha-R*)-alpha-((2S*,5R*)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-hydroxylbenzyl)-N,N-diethylbenzamide, a compound with slow dissociation kinetics, showed the measured rate of G protein activation was not influenced by the agonist switching between receptors. The results are consistent with the idea that the active state(s) of the receptor induced by full or partial agonists is the same, but the number of activated receptors determines the rate of G protein activation.

Topics: Biotransformation; Cell Membrane; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Glioma; GTP-Binding Proteins; Guanosine 5'-O-(3-Thiotriphosphate); Half-Life; Humans; Kinetics; Molecular Conformation; Nalbuphine; Narcotic Antagonists; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, mu; Sulfur Radioisotopes; Tumor Cells, Cultured

The influence of membrane microviscosity on mu-opioid agonist and antagonist binding, as well as agonist efficacy, was examined in membranes prepared from SH-SY5Y cells and from a C6 glioma cell line stably expressing the rat mu-opioid receptor (C6mu). Addition of cholesteryl hemisuccinate (CHS) to cell membranes increased membrane microviscosity and reduced the inhibitory effect of sodium and guanine nucleotides on the affinity of the full agonists sufentanil and [D-Ala2,N-MePhe4,Gly-ol5]enkephalin (DAMGO) for the mu-opioid receptor. Binding of the antagonists [3H]naltrexone and [3H]diprenorphine and the partial agonist nalbuphine was unaffected by CHS. The effect of CHS on agonist binding was reversed by subsequent addition of cis-vaccenic acid, suggesting that the effect of CHS is the result of increased membrane microviscosity and not a specific sterol-receptor interaction. CHS addition increased the potency of DAMGO to stimulate guanosine-5'-O-(3-[35S]thio)triphosphate binding by fourfold, whereas the potency of nalbuphine was unaffected. However, nalbuphine efficacy relative to that of the full agonist DAMGO was strongly increased in CHS-treated membranes compared with that in control membranes. Membrane rigidification also resulted in an increased efficacy for the partial agonists meperidine, profadol, and butorphanol relative to that of DAMGO as measured by agonist-stimulated GTPase activity in control and CHS-modified membranes. These findings support a regulatory role for membrane microviscosity in receptor-mediated G protein activation.

Topics: Animals; Cell Line; Cell Membrane; Cholesterol Esters; Diprenorphine; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalins; Glioma; Guanosine 5'-O-(3-Thiotriphosphate); Membrane Fluidity; Nalbuphine; Naltrexone; Narcotic Antagonists; Narcotics; Neuroblastoma; Protein Conformation; Rats; Receptors, Opioid, mu; Sodium Chloride; Sufentanil; Tumor Cells, Cultured; Viscosity

A therapeutic regimen is described for sedative, analgesic, and anti-emetic effect in patients receiving intra-arterial carmustine (BCNU) for malignant gliomas. This regimen consists of nalbuphine, 30 mg, i.v., and droperidol, 2.5 mg, i.v., given immediately prior to intra-carotid BCNU infusion. Droperidol, 2.5 mg, i.v., is then administered on four hour intervals for sixteen hours post-procedure. This combination provided excellent effect in nine patients treated for twelve intra-carotid infusions. None of the nine patients experienced vomiting, one experienced mild nausea several hours post-infusion, and non complained of severe pain or discomfort. Thirteen additional patients received diazepam, 10 mg, P.O., prior to the intra-carotid BCNU infusion, with fentanyl, 100 mcg, i.v., and prochlorperazine, 10 mg, i.m. at the onset of infusion. All thirteen patients suffered from severe nausea, vomiting, and orbital pain. The nalbuphine/droperidol combination is thought to provide a superior alternative to the traditional narcotic/pheonothiazine/benzodiazepine combination for carotid BCNU infusion. This combination has theoretical advantages for the patient with intracranial mass lesions by providing analgesia and sedation with minimal potential for respiratory depression and carbon dioxide retention.

Topics: Adult; Aged; Brain Neoplasms; Carmustine; Carotid Arteries; Diazepam; Droperidol; Drug Therapy, Combination; Fentanyl; Glioma; Humans; Injections, Intra-Arterial; Middle Aged; Morphinans; Nalbuphine; Nausea; Prochlorperazine; Vomiting