ABT-594 [(R)-5-(2-azetidinylmethoxy)-2-chloropyridine]: a novel, orally effective antinociceptive agent acting via neuronal nicotinic acetylcholine receptors: II. In vivo characterization

The antinociceptive effects of ABT-594, a novel nicotinic acetylcholine receptor (nAChR) ligand, were examined in rats in models of acute thermal (hot box) and persistent chemical (formalin test) pain. Also, the effects of ABT-594 treatment on motor function and electroencephalogram (EEG) were determined. In the hot box and formalin test (i.e., phase 1 and 2), acute treatment with ABT-594 (0.03, 0.1 and 0.3 mumol/kg i.p.) produced significant dose-dependent antinociceptive effects. In the hot box, the efficacy of ABT-594 was maintained after a repeated dosing paradigm (5 days b.i.d.i.p.). ABT-594 was fully efficacious in the formalin test when administered before formalin, and also retained significant efficacy (0.3 mumol/kg i.p.) when administered after formalin injection. The antinociceptive effects of ABT-594 in the hot box and formalin tests were attenuated by pretreatment with the nAChR antagonist, mecamylamine, and in animals treated with the nAChR antagonist chlorisondamine, given centrally (10 micrograms/rat i.c.v. 5 days before), but not in animals pretreated with the opioid receptor antagonist, naltrexone. Acute treatment with ABT-594 produced an initial decrease in open-field locomotor activity, which was absent in animals dosed repeatedly (5 days b.i.d.) with ABT-594. Also, acute treatment with ABT-594 decreased body temperature and decreased the amount of time the animals could maintain balance in an edge-balance test. These effects were no longer present in animals dosed repeatedly with ABT-594. At antinociceptive doses, ABT-594 produced activation of free running EEG in contrast to the sedative-like effects of morphine. Full antinociceptive efficacy was maintained in both the hot box and formalin tests after oral administration, whereas the effects on motoric performance were attenuated. In conclusion, these data demonstrate that ABT-594 is a potent antinociceptive agent with full efficacy in models of acute and persistent pain and that these effects are mediated predominately by an action at central neuronal nAChRs. In addition, antinociceptive effects were maintained after repeated dosing, whereas effects of ABT-594 on motor and temperature measures were attenuated in animals treated repeatedly with ABT-594. Thus, compounds acting at nAChRs may represent a novel approach for the treatment of a variety of pain states.     

N6-(5,6-epoxynorbornyl)adenosine analogs as A1 adenosine agonists

A range of related adenosines and 5'-N-ethylcarboxamidoadenosines bearing oxygenated substituents in the N6 position have been synthesised and evaluated as A1-adenosine receptor ligands. Compound 9 emerged with potent affinity (EC50 = 1.1 nM).     

Apical secretion of a pathogen-elicited epithelial chemoattractant activity in response to surface colonization of intestinal epithelia by Salmonella typhimurium

Modeling Salmonella-epithelial cell interaction in vitro has led to the realization that epithelial cells are crucial in orchestrating neutrophil (PMN) responses, in part by stimulating basolateral release of epithelial chemokines, including IL-8. However, such basolaterally released chemokines, while likely important in orchestration of PMN movement across the subepithelial matrix, are unlikely to be responsible for the final step of transepithelial migration of PMN and entry into the apical compartment. We now show that S. typhimurium attachment to T84 cell apical epithelial membranes induces polarized apical secretion of a pathogen-elicited epithelial chemoattractant (PEEC) bioactivity. Experiments employing semipurified PEEC indicate that it is released in a polarized apical fashion and is sufficient to explain the observed final step of transepithelial migration of PMN induced by Salmonella-apical membrane interaction. By preliminary physical characterization and profiles of PMN activation, PEEC appears to be a novel PMN chemotactic bioactivity. This 1- to 3-kDa nominal molecular mass chemokine-like bioactivity directly stimulates PMN via a pertussis toxin-sensitive receptor and elicits a Ca2+ signal. While these latter features are shared by most other chemokines, analysis of PEEC-elicited PMN activation reveals that, unlike these other agonists, PEEC, even at saturating concentrations, elicits chemotactic activity in the absence of stimulation of superoxide production and/or release of primary and/or secondary granules. These data suggest that the apically released PEEC activity appears to represent a novel epithelial-derived chemoattractant that directs PMN movement across epithelial monolayers.     

Apolipoprotein E antibodies affect the retention of passive avoidance memory in the chick

Isoforms of apolipoprotein E (ApoE) have been implicated as risk factors in Alzheimer's disease. We have, therefore, examined the possible role of ApoE in memory formation, using a one-trial passive avoidance task in day-old chicks. Birds were trained on the task and then at various times pre or post-training were injected intracerebrally with anti-ApoE. Immunofluorescence staining demonstrated the presence of the antibody bound to the neuropil, close to the injection site and adjacent to the ventricle, with a residence time in the brain of up to 30 min. Chicks that were injected 30 min pre-training or just post-training with 5 micrograms/hemisphere of the antibody learned the task, but were amnesic when tested at 30 min or at subsequent times up to 24 hr post-training. When tested at 24 hr, birds injected 5.5 hr post-training showed unimpaired retention. Birds injected with 5 micrograms/hemisphere of anti-ApoA-I (which has a brain distribution similar to that of anti-ApoE) at 30 min pretraining showed no amnesia, indicating the specificity of the effect to the ApoE. Possible mechanisms for this effect are discussed.     

Hypothalamic pro-opiomelanocortin mRNA is reduced by fasting and [corrected] in ob/ob and db/db mice, but is stimulated by leptin

Reduction in the activity of the alpha-melanocyte-stimulating hormone (alpha-MSH) system causes obesity, and infusions of alpha-MSH can produce satiety, raising the possibility that alpha-MSH may mediate physiological satiety signals. Since alpha-MSH is coded for by the pro-opiomelanocortin (POMC) gene, we examined if POMC gene expression would be inhibited by fasting in normal mice or in models of obesity characterized by leptin insufficiency (ob/ob) or leptin insensitivity (db/db). In wild-type mice, hypothalamic POMC mRNA was decreased > 60% after a 2-day fast and was positively correlated with leptin mRNA. Similarly, compared with controls, POMC mRNA was decreased by at least 60% in both db/db and ob/ob mice. POMC mRNA was negatively correlated with both neuropeptide Y (NPY) and melanin-concentrating hormone (MCH) mRNA. Finally, treatment of both male and female ob/ob mice with leptin stimulated hypothalamic POMC mRNA by about threefold. These results suggest that impairment in production, processing, or responsiveness to alpha-MSH may be a common feature of obesity and that hypothalamic POMC neurons, stimulated by leptin, may constitute a link between leptin and the melanocortin system.     

Heterogeneity of beta-adrenoceptors in guinea-pig brain: radioligand binding and cyclic nucleotide generation

In this report, we have examined the radioligand binding and second messenger signalling characteristics of beta-adrenoceptors in the guinea-pig brain. [125I]-Iodocyanopindolol ([125I]ICYP)-labelled sites in the cerebellum and cerebral cortex were of similar densities (Bmax 34 and 24 fmol x mg(-1)) and affinities (K(D) 20 and 55 pM), respectively. Analysis of competition for [125I]ICYP binding in the cerebellum was compatible with the presence of a beta2-adrenoceptor. In this tissue, isoprenaline evoked a cyclic AMP stimulation, and also potentiated cyclic GMP accumulations evoked in the presence of a nitric oxide donor, consistent with mediation via a beta2-adrenoceptor. The [125I]ICYP binding profile in the cerebral cortex did not comply with those previously described for beta-adrenoceptor subtypes, and isoprenaline failed to alter significantly cyclic AMP accumulation in the cerebral cortex, hippocampus, or neostriatum, even in the presence of forskolin or a phosphodiesterase inhibitor. Isoprenaline was also without effect on cyclic GMP accumulation or phosphoinositide turnover in the cerebral cortex. These results suggest that the guinea-pig cerebellum expresses a functional beta2-adrenoceptor coupled to cyclic AMP generation, and potentiation of cyclic GMP accumulation. However, the guinea-pig cerebral cortex displays binding sites that exhibit beta-adrenoceptor-like pharmacology but fail to show functional coupling to cyclic AMP, cyclic GMP, or phosphoinositide signalling systems.     

An open-label dose comparison study of ondansetron for the prevention of emesis associated with chemotherapy prior to bone marrow transplantation

The potentialities of polarization microscopy has been greatly increased by using specific stains for selective enhancement of the optical anisotropy of a macromolecular constituent of cells and tissues. Such stainings have proved to be especially useful in exploring the spatial orientation pattern of the extracellular matrix components. The retardation value, which characterizes quantitatively the degree of submicroscopic orientation, can be measured traditionally with a compensator plate. This technique, however, is time-consuming and greatly dependent on visual judgment. Several attempts have been made to combine digital image analysis and polarization microscopy to improve the measuring technique in unstained structures. In this paper, we summarize theoretical considerations and experimental data to show the advantages and limitations of this methodological approach when using stained and birefringent specimens. The technique we are suggesting is the measurement of the light intensity using a 12 bit cCCD camera attached to a polarized light microscope and digital image analysis system. The theoretical basis is given by the Fresnel equation describing the relationship between light intensity and retardation value. According to this, there is a sin2 function between the light intensity and the retardation value. The same relationship of these two parameters was observed in our experiments on the birefringent extracellular matrix around chondrocytes grown in agarose gel and interterritorial and territorial matrix of canine articular cartilage stained with picrosirius red. Our results suggest that the retardation values can be calculated directly from the light intensity values if the retardation value is lower than lambda/2.     

Leptin receptors in estrogen receptor-containing neurons of the female rat hypothalamus

This study was undertaken to reveal whether integration of the peripheral signals, leptin and estradiol, that convey information on the metabolic state and gonadal function, respectively, might occur in the same hypothalamic neuronal perikarya. Light and electron microscopic immunolabeling for leptin receptors (LRs) and estrogen receptors (ERs) was carried out on hypothalamic sections of female rats. In the medial preoptic area, periventricular regions, including the parvicellular paraventricular nucleus, the arcuate nucleus and the ventromedial hypothalamic nucleus, all of the cells that expressed immunoreactivity for ERs were also immunopositive for LR. On the other hand, only a subpopulation of LR-containing cells was found to express ERs. The extensive colocalization of receptors for leptin and estrogen in neuronal perikarya of all parts of the hypothalamus suggests a closely coupled interaction between these peripheral signals in the regulation of a variety of behavioral and neuroendocrine mechanisms.     

Current local anesthetics in segmental nerve blocks

The evolution of central segmental blockades was studied in 133 patients by using epidural and spinal anesthesias. The efficiencies of 2% Ultracaine (Hoechst) and 2% Lidocaine (Egis) solutions used for epidural anesthesia and 5% Ultracaine (Hoechst) and 0.75% Bupivacaine (Astra) hyperbaric solutions were evaluated. Central segmental blockade induced by Ultracaine was found to be similar to Lidocaine and Bupivacaine in clinical parameters. At epidural blockade, the latent period was identical for the two agents and the duration of analgesia caused by Ultracaine was 20 minutes longer than that with Lidocaine, the consumption of the former being 20% less. At spinal anesthesia, there were no great differences in the depth and duration of conduction block, but with 5% Ultracaine, the analgesic zone was large (13.2 +/- 1.0 and 15.1 +/- 0.6 segments, p < 0.05). No differences were found in the magnitude of hemodynamic changes both with various anesthetics and different types of segmental blockades. The findings make it possible to regard Ultracaine as an drug that has some advantage over Lidocaine for prolonged epidural anesthesia and similar to the latter in pharmacological characteristics. Ultracaine may be regarded as alternative to Bupivacaine for spinal anesthesia.