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Oral self-administration and operant tasks have been used successfully to confirm ethanol′s positive reinforcing effects
in rats. However, in flavor conditioning tasks, ethanol is typically found to have aversive effects. The present studies explored
this apparent paradox by examining the change in value of a flavor paired with orally self-administered ethanol in two different
limited-access procedures. Rats were food-deprived and trained to drink (experiment 1) or to barpress for (experiment 2) 10%
(v/v) ethanol during daily 30-min sessions using prandial initiation techniques. All rats were then exposed to a differential
flavor conditioning procedure in which banana or almond extract was added to the drinking solution. One flavor (counterbalanced)
was always mixed with ethanol (CS+), whereas the other flavor was mixed with water (CS–). By the end of conditioning, rats
in both experiments drank more flavored ethanol than flavored water, confirming ethanol’s efficacy as a reinforcer. Moreover,
barpress rates for CS+ exceeded those for CS– in the operant task. Ethanol doses self-administered in final sessions averaged
about 1 g/kg. The effect of the flavor-ethanol contingency was assessed in preference tests that offered a choice between
the two flavor solutions without ethanol. In both experiments, subjects developed a preference for the flavor that had been
paired with ethanol. Thus, the outcome of flavor conditioning was consistent with that of the oral self-administration tasks
in providing evidence of ethanol’s rewarding effects. These experiments confirm and extend previous studies showing that flavor
aversion is not the inevitable result of flavor-ethanol association in rats. It seems likely that ethanol’s nutrient and pharmacological
effects both contributed to the development of conditioned flavor preference.
Received: 15 February 1997 / Final version: 11 June 1997 相似文献
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Dr. Ludwig Niehus 《Virchows Archiv : an international journal of pathology》1889,118(1):161-186
Ohne Zusammenfassung 相似文献
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Assessment of ethanol's hedonic effects in mice selectively bred for sensitivity to ethanol-induced hypothermia 总被引:3,自引:0,他引:3
Christopher L. Cunningham Cheryl L. Hallett Douglas R. Niehus Jill S. Hunter Lena Nouth Fred O. Risinger 《Psychopharmacology》1991,105(1):84-92
Mice selectively bred for sensitivity (COLD) or insensitivity (HOT) to the hypothermic effect of ethanol were tested in three
tasks purported to assess ethanol's hedonic properties: place conditioning, taste conditioning, and ethanol drinking. In the
place conditioning task, distinctive tactile (floor) stimuli were differentially paired with injection of ethanol (2.25 g/kg)
or saline, and preference for the tactile stimuli was assessed during a choice test without ethanol. In the taste conditioning
task, fluid-deprived mice were given repeated access to saccharin followed by injection of ethanol (2.25 g/kg). In the drinking
task, mice were given access on alternate days to a single drinking tube containing water or ethanol in a concentration that
gradually increased from 1 to 12% (v/v) over days. HOT mice showed greater conditioned preference for ethanol-paired tactile
cues, greater aversion for ethanol-paired flavor cues, and drank less ethanol at concentrations above 5% than COLD mice. HOT
mice also showed higher levels of ethanol-stimulated activity than COLD mice. Control experiments indicated that the lines
did not differ in initial preference for the tactile and flavor stimuli used in the conditioning tasks. Because the same line
differences were seen in mice selected from two genetically independent populations, these studies offer strong evidence of
genetic correlations between ethanol's thermal effect and its effect on activity, place conditioning and taste conditioning.
Evidence of a genetic correlation between ethanol's thermal effect and ethanol drinking, however, is weaker since it is based
on a line difference observed in only one of the genetic replicates. In general, these findings suggest commonality in the
biological mechanisms underlying ethanol's thermal effect and its effect in each behavioral task. This overall pattern of
genetic correlations might indicate that these tasks measure the same motivational effect of ethanol. 相似文献
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Atomic Force Microscopy Studies of Solid Lipid Nanoparticles 总被引:9,自引:0,他引:9
Purpose. Solid Lipid Nanoparticles (SLN) are an alternative carrier system for the controlled delivery of drugs. In most cases prednisolone loaded SLN show a biphasic release behaviour. The initial phase is characterised by a fast drug release, which is followed by a sustained drug release over several weeks.
Methods. The particles are produced by high pressure homogenisation of a lipid (e.g. compritol, cholesterol) dispersed in an aqueous surfactant solution. In this study atomic force microscopy was used to image the original unaltered shape and surface properties of the particles. The crystallinity of the nanoparticles was investigated by differential scanning calorimetry.
Results. The AFM investigations revealed the disc like shape of the particles. From differential scanning calorimetry data it can be concluded that the particle core is in the crystalline state. Additionally it was proven that the particles are surrounded by a soft layer.
Conclusions. Thus it is conceivable that the fast initial drug release during in vitro dissolution tests takes place by drug release of the outer non-crystalline layers of the particles. The following sustained drug release can be assigned to the predisolone release of the inner crystalline particle layers. 相似文献
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Two experiments examined the effect of ambient temperature during ethanol exposure on development of conditioned taste aversion to saccharin. In both studies, male albino rats receiving saccharin-ethanol (1.5 g/kg, IP) pairings followed by 6-h exposure to a 32° C environment developed a weaker saccharin aversion than did rats experiencing ethanol at room temperature. Exposure to the warm environment reduced ethanol-induced hypothermia, but enhanced ethanol's motor-impairing effect. The influence of ambient temperature on ethanol-induced taste aversion may be due to changes in body temperature, neural sensitivity, or elimination rate. Although alternative accounts cannot be entirely dismissed, this outcome suggests that ethanol-induced hypothermia plays a role in determining strength of conditioned taste aversion and thus may be involved in the regulation of oral ethanol intake in rats.
Offprint requests to: C.L. Cunningham 相似文献
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目的探讨急性和慢性呼吸道炎症过程中激肽的生成途径和机制。方法测定支气管肺癌伴阻塞性肺炎,慢性支气管炎和健康对照组支气管肺泡灌洗液(BALF)凝胶过滤前后激肽、激肽形成酶活性(TAMEea),血浆血管舒缓素(PK)和α2巨球蛋白(α2M),并进一步鉴定TAMEea性质。结果急、慢性组TAMEea和激肽水平与健康对照组比较差异有显著性(P<0001,P<0.01),但两组间差异无显著性(P>005);急性组PK和α2M与慢性组比较差异有显著性(P<0001)。凝胶过滤结果显示:急性组BALF的TAMEea最高峰位于分子量约800000处,与第一个α2M峰重叠,而慢性组的最高峰位于40000处。TAMEea抑制试验证实800000处的TAMEea来自于PK;而40000处的TAMEea主要来源于组织血管舒缓素(TK)。结论急性呼吸道炎症的TAMEea主要来自血浆的PK;而慢性呼吸道炎症则以局部组织腺体分泌的TK为主。 相似文献
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Purpose. Assessment of lower size limit of Sedimentation Field-Flow Fractionation (SedFFF), specifically to evaluate if the method is suitable to determine the size and size distribution of 20 nm colloidal gold particles with high resolution.
Methods. Sedimentation Field-Flow Fractionation was used to determine the size of the colloidal particles. Due to the high density of gold it was possible to extend the lower size limit of SedFFF well below 20 nm. The size distribution of a gold colloid was obtained from the peak broadening caused by the polydispersity of the sample. The peak broadening due to instrumental imperfections was determined. For comparison purpose the particles were also sized using SEM and PCS.
Results. The mean diameter of the particles was determined to be (20.87 ± 0.05) nm, the standard deviation in size being 1.04 nm (about 5%). SEM could confirm that the particles are about 20 nm in diameter. A sizing with PCS was not possible. The particles have a strong tendency to aggregate and PCS yields a diameter that is much too large.
Conclusions. At optimized analytical parameters Sedimentation Field-Flow Fractionation is an effective method to measure the size of gold particles as small as 15 nm with an accuracy of about 0.1 nm. The polydispersity of the sample can easily be determined. 相似文献
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Solid lipid nanoparticles (SLN/Lipopearls)--a pharmaceutical and cosmetic carrier for the application of vitamin E in dermal products 总被引:10,自引:0,他引:10
Solid lipid nanoparticles (SLN, Lipopearls) are nanoparticles made from solid lipids by high pressure homogenization. Incorporation of chemically labile active ingredients into the solid lipid matrix protects against chemical degradation, which is shown for vitamin E. The SLN are physically stable in aqueous dispersions and also after incorporation into a dermal cream as proven by photon correlation spectroscopy and differential scanning calorimetry. Electron microscopy and atomic force microscopy data reveal the spherical shape of the SLN and the detailed structure of the particle surface. Ultrafine particles form an adhesive film leading to an occlusive effect on the skin. The occlusion promotes the penetration of vitamin E into the skin, as shown by the stripping test. In addition to chemical stabilization of active ingredients, occlusive effects on the skin and subsequent enhanced penetration of compounds, the SLN also possess a pigment effect covering undesired colours leading to an increased aesthetic acceptance by the customer. 相似文献