Bremazocine reduces unrestricted free-choice ethanol self-administration in rats without affecting sucrose preference

It has been postulated that opioid systems in the brain may play a role in ethanol reinforcement. In this respect, μ- and δ-opioid receptors may mediate the rewarding effects whereas κ receptors are thought to mediate the aversive effects of opioids. Accordingly, long-acting benzomorphans such as bremazocine, that simultaneously act as μ and δ receptor antagonists and κ receptor agonists may be particularly effective in reducing ethanol self-administration. Therefore, we studied the effect of bremazocine on oral ethanol self-administration in rats using a paradigm [unrestricted free-choice drinking of 10% (v/v) ethanol], previously shown to cause long-term neuroadaptations in the nucleus accumbens and caudate putamen. Bremazocine (0.1 mg/kg, once daily for five consecutive days) reduced ethanol drinking by about 50% during the active period of the animals, whereas the intake of sucrose (3–10% w/v) was affected neither in naive nor in ethanol-experienced rats. This effect of bremazocine appeared not to be secondary to its acute sedative effect or the slight increase in total fluid consumption. Unlike bremazocine, the selective κ-opioid receptor agonist U50,488H (10 mg/kg, once daily) inhibited ethanol drinking only during the first of 5 treatment days and the opioid receptor antagonist naltrexone (0.3–10 mg/kg, once daily) only caused a modest (about 20%) suppression of ethanol drinking during the first hours after drug injection. Thus, bremazocine appears to be far more potent than the clinically applied drug naltrexone in this respect. Our data further support the role of opioid receptors in ethanol reinforcement and indicate that long-acting mixed-action opioids such as bremazocine may be useful as adjuvants for the clinical management of ethanol addiction. Received: 1 July 1998/Final version: 3 September 1998     

Amacrine cells,bipolar cells and ganglion cells of the cat retina: A Golgi study

Neuronal types contributing to the inner plexiform layer of the cat retina are described based primarily on light microscopy of Golgi-impregnated retinal whole-mounts. Cells have been characterized on morphological criteria that include dendritic branching patterns, dendritic tree sizes, cell body sizes and stratification of processes in the inner plexiform layer. Nine different types of bipolar cell, 22 different types of amacrine cell and 23 different types of ganglion cell can be distinguished using one or more of these morphological criteria. The significance of the different morphological types of cells is discussed, particularly in relationship to the functional bisublamination of the cat inner plexiform layer.     

Binding of psychotropic drugs to isolated alpha-acid glycoprotein

Alpha1-acid glycoprotein (alpha1-AG) was purified from human sera, and its binding properties with respect to psychotropic drugs were examined by equilibrium dialysis methods in order to clarify the specificity of binding. Radioactive imipramine, a tricyclic antidepressant, was used as the primary ligand. Other drugs, representative of different classes, were tested as potential inhibitors of the alpha1-AG-imipramine binding. The K(a) for imipramine was 2.8 x 10(5) (+/- 0.8) M(-10 (mean +/- S.D.). Chlorpromazine, fluphenazine, thioridazine, loxapine and thiothixene, which are antipsychotic drugs, were competitive inhibitors of imipramine binding, and their K(a) values were in the same range. Propranolol, haloperidol and diazepam were also competitive inhibitors but their affinities were lower. Molindone, an indolic antipsychotic, when tested at the same concentrations as the other drugs, did not affect imipramine binding. Trihexyphenidyl, an anti-Parkinson drug, was a potent but noncompetitive inhibitor. These data identify the antidepressant and major tranquilizer drugs that exhibit high affinity for alpha1-AG and indicate that alpha1-AG may account for 40 per cent of total imipramine bound in serum. Since in psychiatric clinical practice two drugs are frequently administered together, possible competitive effects are discussed as well as the potential role of alpha1-AG in psychiatric illness.     

Specific staining of the axon membrane at nodes of Ranvier with ferric ion and ferrocyanide

Ferric ion and ferrocyanide were used as stains for light and electron microscopy of peripheral nerves. In rat sciatic nerves, it was found that ferric ion preferentially binds to the cytoplasmic surface of the axon membrane at nodes of Ranvier but not at internodal regions. In myelinated axons in the electric organ of the gymnotid fish, Sternarchus albifrons, the small excitable nodes are similarly stained, but the larger inexcitable nodes are not stained by ferric ion. Staining of the inner surface of the nodal membrane appears to be related to a structural specialization of this membrane, rather than accessibility to stain. Our data thus show a chemical differentiation of the inner surface of the axon membrane between nodes and internodes in normal peripheral nerve fibers and between the inner surface of the axon membrane at active nodes, inactive nodes, and the internodes in the Sternarchus electrocyte axons.     

Reserpine as an uncoupler of oxidative phosphorylation and the relevance to its psychoactive properties

Many drugs differing widely in chemical structure uncouple mitochondrial oxidative phosphorylation in vitro. This observation has led to the hypothesis that in vivo uncoupling is the basis of their pharmacological activity. Serpasil, a parenteral preparation of reserpine, recently has been shown to uncouple oxidative phosphorylation in vervet monkey kidney mitochondria. Although the drug exhibits some properties of a "classical" uncoupler, our studies show that it has a dual effect on energy conservation. Reserpine released respiratory control in rat liver mitochondria only when dissolved in organic solvents (as in Serpasil) or when deprotonated. Reserpine also released the oligomycin-induced respiratory control in beef heart submitochondrial particles, and inhibited energized uptake of Ca2- by rat liver mitochondria. Reserpine had a dual effect on mitochondrial ATPase: It (a) enhanced ATP hydrolysis by intact liver mitochondria, and (b) inhibited ATP hydrolysis by submitochondrial particles of beef heart. On a molar basis, reserpine was less effective than carbonyl cyanide 3-chlorophenylhydrazone in all bioenergetic reactions examined. Homogenates and mitochondria isolated from brain and liver of rats stuporous from intraperitoneally injections of Serpasil exhibited no detectable abnormalities in respiratory states and responded to known uncouplers in the expected manner. There was no evidence of in vivo uncoupling of oxidative phosphorylation as a basis of the pharmacological activity of reserpine, although interference with energy transfer may be involved in toxic manifestations of the drug. The results indicate the need for caution in interpreting the action of drugs formulated in complex pharmaceutical preparations and based solely on in vitro experiments.     

Effect of low-dose phenobarbital on hepatic microsomal UDP-glucuronyl transferase activity

To determine whether hepatic microsomal enzyme induction occurs in rats following administration of phenobarbital at doses similar to those used in humans (0.5 to 7.5 mg/kg), UDP-glucuronyl transferase (UDPGT) and cytochrome P-450 activities were measured in liver homogenate and microsomal preparations from control rats and rats treated for 6 days with phenobarbital at 1 and 3 mg per kg per day. While no significant increases in liver weight and protein content of homogenate and microsomal preparations were observed with either dose of the drug, both UDPGT and P-450 activities were enhanced significantly following administration of phenobarbital at 3 mg per kg per day. The activity of P-450 was increased by approximately 30% and that of UDPGT by 15-24 and 45-66%, respectively, employing bilirubin and p-nitrophenol as the acceptor substrate. The extent of induction of bilirubin or p-nitrophenol UDPGT was similar when measured with "native" enzyme or with enzyme activated by UDP-N-acetyl glucosamine, digitonin or deoxycholate. These data suggest that the discordant effects of phenobarbital on UDPGT and cytochrome P-450 previously reported in humans and rats may not be attributable solely to differences in the drug doses employed.     

Polyamine involvement in the secretion and action of TGF-α in hormone sensitive human breast cancer cells in culture

These experiments were designed to test polyamine (PA)* involvement in the secretion and action of transforming growth factor (TGF-) in hormone responsive MCF-7 breast cancer cells in liquid culture. At the same time, we evaluated the influence of culture conditions (with serum vs. serum depleted) and subclonality of MCF-7 cells on PA involvement in estrogen (E₂) and TGF- stimulated cell proliferation. Despite inducing a profound suppression of cellular PA levels and inhibiting basal and E₂-stimulated growth, administration of the PA synthesis inhibitor -difluoromethylornithine (DFMO) did not influence either basal or E₂-induced TGF- secretion. In the same experiments, on the other hand, addition of DFMO completely blocked the growth stimulatory effect of exogenous TGF-. However, when the culture conditions were changed to serum-free medium, TGF- and E₂-induced cell proliferation was affected modestly or not at all by DFMO administration, despite similar suppression of cellular ornithine decarboxylase (ODC) activity and PA levels. In addition, different clones of MCF-7 cells differed in their sensitivity to the antiproliferative effect of DFMO as well as in basal levels of ODC activity and PA. We conclude that PAs are not involved in basal or E₂-stimulated TGF- secretion in MCF-7 breast cancer cells. On the other hand, PAs do seem to be important mediators of TGF- and E₂-induced breast cancer cell proliferation, though the degree of such involvement appears to be influenced by serum factors and clonal variability of MCF-7 cells.     

Phase I evaluation of 773U82-HCl in a two-hour infusion repeated daily for three days

One of a novel series of compounds (AMAPS or arylmethylaminopropanediols), 773U82-HCl has shown significant antitumor activity inin vitro and inin vivo tumor systems, but has less animal CNS toxicity than the lead compound in the same series (crisnatol). This study was designed to evaluate the pharmacokinetics, qualitative and quantitative toxicities of 773U82-HCl and to determine the recommended phase II dose (MTD) of 773U82-HCl given as a short infusion daily for 3 days every 3 weeks. Twenty-nine patients with refractory malignancies received 79 courses over 9 dose levels during this study. Doses ranged from 50 to 1060 mg/m²d×3 days. Due to the possibility of local hemolysis with concentrations > 1.5 mg/ml, drug was administered in solutions containing 1.5 mg/ml. Because large volumes were needed at the higher dose levels, the infusion duration was increased from 2 hours to 4 hours. Mild to moderate nausea, vomiting, fatigue, dizziness and headaches were observed. Myelosuppression was the dose limiting toxicity. The recommended phase II dose and schedule was determined to be 800 mg/m²d×3d every 3 weeks. 773U82-HCl plasma concentration-time data were analyzed using a two-compartment pharmacokinetic model. The t1/2 averaged 6 hours and the total body clearance was 75.9 L/hr/m². The volume of distribution (Vdss) was large, averaging 470 L/m².Abbreviations ECG electrocardiogram - t^1/2 half-life - Vdss volume of distribution - HPLC highperformance liquid chromatography - Vd_ss steady-state volume of distribution - AUC area under the concentration × time curve - CL total body clearance - C_max peak plasma level - V_c central volume of distribution