Inhibition of growth in young mice treated with pentazocine: reversal by naltrexone

One week old mice were injected subcutaneously once daily with d,1-methadone (5 mg/kg), pentazocine, naltrexone, naloxone, nalorphine or nalbuphine, each at 10 mg/kg. The remaining half of each litter was used as control. Only methadone and pentazocine groups showed reduced weight gain after 3 weeks of treatment (P < 0.01). Injection of pentazocine in dosages of 5-20 mg/kg inhibited weight gain and protein synthesis in a dose-related manner. The incorporation of labeled leucine was followed in brain, liver and muscles. Methadone and pentazocine groups showed a significant decrease in protein synthesis in all tissues studied. The nalbuphine, nalorphine, naloxone, and naltrexone-treated groups incorporated leucine normally, correlating with normal weight gain. These data suggest that pentazocine, unlike the other mixed agonist-antagonists and antagonists, adversely affects the growth of very young animals when administered chronically. A specific opioid effect is suggested by the fact that naltrexone given concomitantly with the pentazocine prevents development of the biochemical lesion.     

Effect of RU-38486 on dexamethasone reversal of morphine-induced constipation in mice.

1. Morphine and dexamethasone significantly reduce gastrointestinal transit in mice. The degree of reduction was greater for morphine. 2. Dexamethasone pretreatment was found, however, to antagonize morphine-induced constipation. 3. Cycloheximide does not modify the dexamethasone effects. 4. RU-38486 reverses both the inhibitory action of dexamethasone on gastrointestinal transit and its reducing effect on morphine-induced constipation. 5. These results suggest that dexamethasone might act through binding to receptors not linked to DNA-responsive elements.     

Blockade of morphine-induced place preference by diazepam in mice

The effects of diazepam on morphine-induced place preference were examined in mice. Pretreatment with diazepam (2 mg/kg i.p.) 30 min prior to morphine injection significantly abolished the morphine (5 mg/kg s.c.)-induced place preference, and this effect of diazepam was antagonized by pretreatment with flumazenil. In addition, pretreatment with diazepam prevented the morphine (5 mg/kg s.c.)-induced increase in dopamine turnover in the limbic forebrain. These results suggest that pretreatment with diazepam may suppress the rewarding effects of morphine.     

MPTP-induced hypoactivity in mice: reversal by L-dopa

Three experiments were performed to study the subchronic effects of treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 2 x 40 mg/kg subcutaneously two weeks before testing) in C57 BL/6 mice upon spontaneous motor activity and the reversal of the long-term behavioural changes by acute treatment with L-Dopa. Mice treated with MPTP showed a drastic reduction of striatal dopamine levels (-88%) associated with reductions of all three parameters of spontaneous motor activity, i.e. locomotion, rearing and total activity, during both the initial, exploratory, stage (first 90 min), and later stages of the 3- or 4-hr test periods. L-Dopa (5-80 mg/kg subcutaneously) injected 60 min. after the start of testing dose-dependently improved all three parameters studied in MPTP treated mice with 10 mg/kg being the lowest dose causing a significant effect, while doses above 20 mg/kg caused hyperactivity. During the initial period, rearing activity in MPTP mice was to a variable degree suppressed by the L-Dopa treatment (20-80 mg/kg); these reductions were followed by enormous increases in motor activity by the 40 mg/kg (locomotion) and 80 mg/kg (total activity) L-Dopa groups. Both the degree and duration of the L-Dopa-induced hypoactivity for locomotor behaviour increased dose-dependently in control mice. No suppressive effects of L-Dopa were obtained for total activity in control mice, although the 80 mg/kg L-Dopa doses evoked hyperactivity for up to 90 min. following treatment for both locomotion and total activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cross-reinstatement by cocaine and amphetamine of morphine-induced place preference in mice

The cross-reinstatement by psychostimulants of a conditioned place preference (CPP) induced by morphine was evaluated in mice. In Experiment 1, we examined the effects of a single dose of cocaine and amphetamine on a previously extinguished morphine CPP. After acquisition of CPP induced by morphine (40 mg/kg), animals underwent daily extinction sessions of 15 min duration until the CPP was extinguished. Subsequently, animals received a non-contingent injection of cocaine (25 mg/kg) or amphetamine (4 mg/kg), which produced the reinstatement of the extinguished morphine-induced CPP. In Experiment 2, we evaluated the reinstating effects of several priming doses of cocaine (Experiment 2A) or amphetamine (Experiment 2B). As in the first experiment, after conditioning with morphine (40 mg/kg), mice underwent daily 15 min extinction sessions. When the preference was no longer evident, we tested the effects of cocaine (0, 6.25, 12.5, 25 and 50 mg/kg) and amphetamine (0, 0.5, 1, 2 and 4 mg/kg) on the reinstatement of CPP. Doses from 12.5 mg/kg of cocaine upward and doses from 1 mg/kg of amphetamine upward effectively reinstated CPP. Our results demonstrate cross-reinstatement with psychostimulants and opiates, suggesting that in abstinent individuals, drug exposure can produce craving for the previously abused drug and relapse.     

Regulation of hepatic cholesterol metabolism in CETP/LDLr mice by cholesterol feeding and by drugs (cholestyramine and lovastatin) that lower plasma cholesterol

1. The hepatic mechanisms involved in the simultaneous regulation of plasma cholesterol concentration and cholesteryl ester transfer protein (CETP) activity were investigated by sharply modifying the hepatic rates of cholesterol synthesis. This was accomplished by cholestyramine, lovastatin and cholesterol feeding in human CETP transgenic mice cross-bred with low-density lipoprotein receptor (LDLr)-knockout mice, generating CETP(+/-)/LDLr(+/-) mice, which present a plasma lipoprotein profile resembling that of humans. 2. Analyses of pooled data showed that the plasma CETP activity correlated positively with plasma total cholesterol concentration, hepatic CETP mRNA and the liver microsomal cholesterol content; a negative correlation was found between plasma CETP activity and the liver 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and LDLr mRNA levels. These coordinated events represent an efficient control system that stabilizes the cell cholesterol content. 3. Nonetheless, not all cholesterol metabolism regulatory systems seem to fit into a coherent pattern of responses, suggesting that other unknown cellular mechanisms play roles depending on the type of pharmacological intervention. 4. For example, microsomal cholesterol content was not affected by cholestyramine, but was increased on cholesterol feeding (as predicted), and, surprisingly, on lovastatin treatment. Furthermore, although both plasma cholesterol-lowering drugs increased CYP7A1 mRNA and had no effect on CYP27 mRNA, other metabolic components were differentially modified. Cholestyramine and lovastatin, respectively, did not modify and increased both HMG-CoA and sterol responsive element binding protein 1c mRNA, did not modify and lowered liver X receptor alpha mRNA, lowered and increased ATP binding cassette A1 mRNA and lowered and did not modify scavenger receptor B1 mRNA. 5. That is, different to unabsorbed cholestyramine, lovastatin, as an absorbed plasma cholesterol-lowering drug, may have modified the activity of other unknown genes that play roles in the interaction of CETP with the metabolism of hepatic cholesterol.     

Nicotine potentiation of morphine-induced catalepsy in mice

In the present study, effects of nicotine on catalepsy induced by morphine in mice have been investigated. Morphine but not nicotine induced a dose-dependent catalepsy. The response of morphine was potentiated by nicotine. Intraperitoneal administration of atropine, naloxone, mecamylamine, and hexamethonium to mice reduced catalepsy induced by a combination of morphine with nicotine. Intracerebroventricular injection of atropine, hexamethonium, and naloxone also decreased catalepsy induced by morphine plus nicotine. Intraperitoneal administration of atropine, but not intraperitoneal or intracerebroventricular injection of hexamethonium, decreased the effect of a single dose of morphine. It was concluded that morphine catalepsy can be elicited by opioid and cholinergic receptors, and the potentiation of morphine induced by nicotine may also be mediated through cholinergic receptor mechanisms.     

Lipopolysaccharide-mediated immobility in mice: reversal by cyclooxygenase enzyme inhibitors

Endotoxin (lipopolysaccharide, LPS) is known to activate the hypothalamo-pituitary adrenocortical axis, as well as norepinephrine and indolamine metabolism. In the present study we examined the effects of systemically administered LPS on forced swimming-induced despair behavior in mice. LPS (50 micrograms/mouse i.p.) time-dependently enhanced the forced swimming-induced immobility period. The increase in immobility time was highest after 2 h of LPS administration. Desipramine (10 mg/kg), a tricycle antidepressant, or fluoxetine (10 mg/kg), a serotonin reuptake inhibitor, significantly reversed the LPS-induced increase in immobility time. Cyclooxygenase inhibitors nimesulide (1, 2 and 5 mg/kg), naproxen (10 mg/kg) and rofecoxib (2 mg/kg) did not alter the despair behavior per se. Nimesulide (10 mg/kg) did reverse reserpine-induced immobility. Nimesulide (2 mg/kg), naproxen (10 mg/kg) and rofecoxib (2 mg/kg) significantly reversed LPS-mediated despair behavior. The present study demonstrated that LPS-induced inflammatory responses in the brain may cause despair behavior. Reversal with a cyclooxygenase inhibitor indicates the role of prostaglandins in despair behavior.     

HPLC法测定小鼠血浆和组织中伊曲康唑的含量

目的建立高效液相色谱法测定小鼠血浆和组织中伊曲康唑的含量.方法采用色谱柱:Diamosil C18(4.6mm×150mm,5μm);流动相:甲醇-水(84∶16,V/V);流速:1.0mL·min-1;检测波长:262nm;柱温:室温;进样量:20μL,按伊曲康唑峰计理论塔板数不小于3000,来测定小鼠血浆和各组织中伊曲康唑的含量.结果小鼠血浆和各组织器官日内精密度和日间精密度RSD均小于4%;小鼠血浆方法回收率大于97%,RSD均小于3%;小鼠各组织器官方法回收率均大于95%,RSD均小于4%;可满足生物样品分析方法的要求.结论建立的HPLC法测定血浆和组织伊曲康唑的浓度,方法简便,准确,内源性物质不干扰测定,适合于大批量生物样本中伊曲康唑含量的测定.     

Influence of glycine on morphine-induced antinociception in mice

The effects of glycine on morphine-induced antinociception were investigated in mice, using a cutaneous thermal test (hot-plate), a visceral chemical test (acetylcholine writhing test), and a locomotor activity test. When glycine (200 mg/kg p.o.) and morphine (5 mg/kg s.c.) were given together during the first 30 min, glycine first antagonized the morphine-induced antinociception then this was followed by a synergistic effect. The two-phase influence of glycine on morphine-induced antinociception may be due to the interaction of glycine with different receptors.     

曲马朵对吗啡所致小鼠僵住症的影响

目的　观察曲马朵是否对吗啡所致小鼠僵住症产生影响及其作用机制。方法　采用“抓棒”实验测定小鼠的僵住持续时间。结果　①曲马朵在10～ 90mg·kg- 1范围内不能诱发小鼠产生僵住症 ,但呈剂量依赖性抑制 4 0mg·kg- 1吗啡诱发的小鼠僵住症 ;②氟西汀 (2 0 ,30和 4 0mg·kg- 1)、吗氯贝胺(12 .5 ,2 5 ,5 0mg·kg- 1)、5 羟色氨酸 (12 .5 ,2 5和 5 0mg·kg- 1)增强曲马朵抑制吗啡所致小鼠僵住症的作用 ;③对氯苯丙氨酸 (30 0和 35 0mg·kg- 1)拮抗曲马朵对吗啡所致小鼠僵住症的抑制作用。结论中枢 5 HT能神经系统参与曲马朵对吗啡所致小鼠僵住症的抑制作用。     

Enhancement of stress-induced analgesia in adrenalectomized mice: Its reversal by dexamethasone

Adrenalectomy significantly increased the level of analgesia induced by room temperature swimming in mice, as revealed by a hot-plate test. This augmentation of antinociceptive action of stress was abolished by dexamethasone pretreatment. Involvement of pituitary opioids in modulating post-stress pain sensitivity in mice is suggested.     

Study of morphine-induced dependence in gonadectomized male and female mice

In this study we evaluated the effects of sex difference and also sex hormones on the naloxone-precipitated morphine withdrawal in both orchidectomized (ORC) male and ovariectomized (OVX) female mice. Morphine (50, 50 and 75 mg/kg/day for 4 days, s.c.) was administered to animals and at 5th day naloxone (4 mg/kg, i.p.)-precipitated morphine withdrawal signs, jumpings and the percentage of weight loss, were measured. There was no significant alteration in withdrawal jumpings between male and female mice, though weight loss was significantly higher in male ones. Jumpings was significantly lower in both OVX and ORC mice and percentage of weight loss was significantly higher in OVX mice than corresponding non-operated or sham animals. In OVX mice, E₂V (10 mg/kg, s.c.) increased number of jumpings and decreased percentage of weight loss. Progesterone (25 mg/kg, s.c.) had no effect on jumpings, whereas it decreased weight loss in OVX mice. Testosterone (2.5 mg/kg, s.c.) increased jumpings in ORC mice while it had no effect on percentage of weight loss. Our results demonstrated that sex hormones could play a role in the morphine withdrawal syndrome in both ORC male and OVX female mice.     

Agmatine potentiates morphine-induced conditioned place preference in mice: modulation by alpha2-adrenoceptors.

The effects of agmatine, an endogenous polyamine metabolite formed by decarboxylation of L-arginine, and its combination with morphine on conditioned place preference (CPP) has been investigated in male mice. Our data show that subcutaneous administration of morphine (1-7.5 mg/kg) significantly increases the time spent in the drug-paired compartment in a dose-dependent manner. Intraperitoneal administration of agmatine (1-40 mg/kg) alone does not induce either CPP or conditioned place aversion, while combination of agmatine and subeffective doses of morphine leads to potent rewarding effects. Lower doses of morphine (0.1, 0.05, and 0.01 mg/kg) are able to induce CPP in mice pretreated with agmatine 1, 5, and 10 mg/kg, respectively. Concomitant intraperitoneal administration of UK 14 304 (0.5 mg/kg), a highly selective alpha2-agonist, with per se noneffective dose of morphine (0.5 mg/kg) and also its combination with noneffective doses of agmatine (1 mg/kg) plus morphine (0.05 mg/kg) produces significant CPP. UK 14 304 (0.05, 0.5 mg/kg) alone, or in combination with agmatine (1, 5 mg/kg) have had no effect. We have further investigated the possible involvement of the alpha2-adrenoceptors in the potentiating effect of agmatine on morphine-induced place preference. Selective alpha2-antagonists, yohimbine (0.005 mg/kg) and RX821002 (0.1, 0.5 mg/kg), block the CPP induced by concomitant administration of agmatine (5 mg/kg) and morphine (0.05 mg/kg). Yohimbine (0.001-0.05 mg/kg) or RX821002 (0.05-0.5 mg/kg) alone or in combination with morphine (0.05 mg/kg) or agmatine (5 mg/kg) fail to show any significant place preference or aversion. Our results indicate that pretreatment of animals with agmatine enhances the rewarding properties of morphine via a mechanism which may involve alpha2-adrenergic receptors.     

粉防己碱对小鼠吗啡位置偏爱效应的影响(英文)

利用条件性位置偏爱实验研究钙拮抗剂粉防己碱对小鼠吗啡奖赏效应的影响 .实验采用有倾向性程序 .吗啡 ( 5mg· kg-1,sc,每日 1次 ,5d)引起小鼠显著的位置偏爱效应 .在训练阶段每天 sc吗啡前 30 min预先给予粉防己碱 ( 1 0 ,2 0和 40 mg·kg-1,ip)可剂量依赖性地抑制吗啡引起的小鼠位置偏爱效应 .而粉防己碱 ( 1 0 ,2 0和 40 mg· kg-1,ip)只在测试前 30 min给药 1次 ,不影响吗啡已形成的小鼠位置偏爱 .结果说明粉防己碱能有效地抑制吗啡偏爱效应的获得 ,但不影响其表达 .     

Effects of naloxone and naltrexone on drug-induced hypothermia in mice

The hypothermia produced by injecting apomorphine into mice was potentiated by morphine; it was antagonized by haloperidol, by naloxone and by naltrexone. The hypothermic responses to morphine, chlorpromazine and ethanol were also blocked by naltrexone. However, naltrexone potentiated the hypothermic response to pentobarbital. Tolerance to morphine, produced by subcutaneous implantation of a morphine pellet, was accompanied by cross-tolerance to apomorphine-induced hypothermia. Animals made tolerant to apomorphine were not tolerant to morphine-induced hypothermia. The dopamine supersensitivity resulting from chronic treatment with haloperidol potentiated the hypothermic response to apomorphine but not to morphine. These results suggest that endogenous opioids may serve as mediators in the control of thermoregulation by dopamine.     

Stereospecific accumulation of dihydromorphine and naltrexone by corpus striatal slices of morphine-dependent mice

Stereospecific accumulation of [3H]dihydromorphine and [3H]naltrexone by striatal slices from morphine-dependent mice was examined in Krebs-Ringer bicarbonate medium. Striatal slices showed a saturable and stereospecific accumulation of both [3H]ligands. The accumulation constant of naltrexone, determined by Wilkinson's analysis, was significantly decreased in both morphine-dependent mice and dependent mice abruptly withdrawn for 6 hr. The maximal accumulation of naltrexone was not changed in withdrawn mice, but decreased in dependent mice. This could be due to the high concentration of residual morphine in the slices. There were no significant differences in the accumulation constant or maximal accumulation of dihydromorphine among the striatal slices from control, dependent and withdrawn mice. These data indicate that in morphine-dependent mice, there is an increased affinity of the opioid receptors for the narcotic antagonist, naltrexone but not for the agonist, dihydromorphine.     

白藜芦醇降低高脂小鼠体内胆固醇水平的作用及胆汁酸转化分子机制的初步研究

目的：研究白藜芦醇对高脂小鼠体内胆固醇水平的降低作用及其调节胆汁酸转化的分子机制。方法：选取40只Apo E-/-小鼠给予高脂饮食制备高胆固醇小鼠模型，随机分为4组：模型组、白藜芦醇低剂量组、白藜芦醇中剂量组及白藜芦醇高剂量组，分别每天灌胃0.2 mL 生理盐水、10 g·L^-1白藜芦醇，20 g·L^-1白藜芦醇和40 g·L^-1白藜芦醇。分别在第0，5，10，20周比较4组小鼠血浆总胆固醇（total cholesterol，TC）、三酰甘油（triglyceride，TG）的水平。在第20周实验结束时，比较4组小鼠血浆低密度脂蛋白胆固醇（low density lipoprotein cholesterol，LDL-C）、高密度脂蛋白胆固醇（high density lipoprotein cholesterol，HDL-C）含量、动脉粥样硬化指数（arteriosclerosis index，AI）水平以及肝脏中TC、TG的含量。在人肝癌细胞株HepG2细胞系中加入0，6.25，12.5，25 μmol·L^-1白藜芦醇，检测加入白藜芦醇后各组细胞内胆固醇含量、细胞外胆汁酸含量差异。最后用25 μmol·L^-1白藜芦醇处理细胞，采用RT-PCR及Western blot分别检测细胞中胆固醇代谢相关基因胆固醇7-羟化酶（cholesterol 7α-hydroxylase，CYP7A1）、腺苷三磷酸结合盒转运体超家族成员（ABCG5）的mRNA及蛋白的表达水平。结果：白藜芦醇各剂量组小鼠的TC、TG、LDL-C、AI水平均显著低于模型组，而HDL-C显著高于模型组。白藜芦醇可降低HepG2细胞中总胆固醇含量，并促进细胞分泌胆汁酸含量。RT-PCR及Western blot结果显示，25 μmol·L^-1白藜芦醇处理HepG2细胞后，CYP7A1、ABCG5的mRNA及蛋白的表达水平明显增加。结论：白藜芦醇可以降低高脂小鼠体内胆固醇水平，这种作用可能是通过调节胆汁酸转化过程中相关基因CYP7A1、ABCG5的表达来实现的。     

5-羟色胺酸对吗啡诱导小鼠行为敏化的影响

研究中枢5-羟色胺能系统对吗啡诱导小鼠行为敏化的介导作用。选用雄性昆明小鼠，每天2次注射生理盐水或吗啡10mg／kg，连续3天。停药5天后，于第9天，进行吗啡激发试验，测定小鼠的自主活动60min，观察行为敏化效应。此外，选用5-羟色胺前体物质5-羟色氨酸作为工具药，分别在吗啡处理阶段（形成期），吗啡停药阶段（转换期）以及吗啡激发试验前腹腔注射20-80mg／kg5-羟色氨酸。激发试验给予吗啡后，立即测定小鼠的自主活动。实验第9天激发试验数据表明，每天2次反复给予吗啡的小鼠，其自主活动明显高于生理盐水对照组，说明小鼠对吗啡产生了行为敏化效应。5-羟色氨酸可以选择性抑制吗啡对小鼠行为敏化的诱导作用，其抑制作用呈剂量依赖性。然而，5-羟色氨酸对小鼠吗啡行为敏化的转换和表达无明显药理作用。因此，中枢5-羟色胺能系统的功能水平上调可能对吗啡诱导小鼠行为敏化效应具有一定的抑制作用。     

Strain-dependent effects of anandamide on memory consolidation in mice are antagonized by naltrexone

Post-training administration of anandamide (1.5, 3, 6 mg/kg) dose-dependently impaired retention of an inhibitory avoidance response in DBA/2 mice, while improving it in C57BL/6 mice. The effects on retention performance induced by the drug appear to be due to an effect on memory consolidation. They were observed when drug was given at short, but not long, periods of time after training, i.e. when the memory trace was susceptible to modulation. These effects of anandamide parallel those of opioid agonists, as previously reported. Moreover, the opioid antagonist naltrexone improved retention in DBA/2 mice, while impairing it in C57BL/6 mice. Pre-treatment with the opioid antagonist at a non-effective dose (0.1 mg/kg) antagonized the effects of anandamide on memory consolidation in both strains. These results strongly suggest that endogenous cannabinoids affect memory processes through opioid systems. The possible involvement of other neurotransmitter systems, such as dopamine, in strain-dependent effects of anandamide in memory consolidation is discussed.