Inhibition by immunophilin ligands of morphine-induced tolerance and dependence in guinea pig ileum

Immunophilin ligands, cyclosporine A and FK506 (tacrolimus), besides their immunosuppressive action, have several effects on different neural functions, such as modulation of the release of many neurotransmitters, the reduction of nitric oxide (NO) production by the inhibition of dephosphorylation of neuronal nitric oxide synthase (nNOS) and the alteration of the expression of certain genes. Many of these actions apparently occur through the inhibition of calcineurin, a calcium-calmodulin-dependent phosphatase. On the other hand, several studies have shown that NO has a critical role in opioid-induced tolerance and dependence in both in vivo and in vitro models. In the present study, the effect of cyclosporine A and FK506 on the development of tolerance to and dependence on morphine in the guinea pig ileum was assessed. Morphine inhibited electrically stimulated twitch of ileum in a concentration-dependent manner (pD(2)=7.45+/-0.07). Tolerance to this effect was induced by incubation of ileum with 2 x IC(50) or 4 x IC(50) of morphine for 2 h that induced a degree of tolerance of 6.81 and 18.10, respectively. The co-incubation of ileum with morphine along with either cyclosporine A or FK506 reduced the degree of tolerance significantly (P<0.05) and restored the sensitivity of ileum to the morphine inhibitory effect. Dependence was induced by incubation with 4 x IC(50) of morphine for 2 h and was assessed based on naloxone-induced contractions (10(-5) M). Cyclosporine A (10(-9) M) and FK506 (10(-9) M) can attenuate the development of dependence to morphine as shown by the significant decrease in naloxone-induced contractions (P<0.05). These results suggest that immunophilin ligands at very low concentrations (nanomolar) can reduce the induction of acute tolerance to and dependence on morphine in the myenteric plexus of guinea pig ileum.     

The role of the NO/NMDA pathways in the development of morphine withdrawal induced by naloxone in vitro.

The effect of nitric oxide (NO)/N-methyl-d-aspartate (NMDA) pathways on naloxone-induced withdrawal contracture was studied in vitro in a model of acute morphine dependence in the isolated guinea pig ileum. Exposure of the isolated guinea pig ileum to morphine (10(-5) M) for 5 min resulted in acute dependence, characterized by a strong withdrawal contracture induced by naloxone (5x10(-5) M). The NO synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME; 5x10(-4) M) as well as the soluble guanylate cyclase inhibitor methylene blue (MB; 10 microM) were found to significantly attenuate the naloxone-induced withdrawal contracture. In addition, the NO precursor L-arginine (5x10(-4) M) as well as the NO donors sodium nitroprusside (SNP; 1 microM) and sodium azide (NaZ; 10 microM) were able to revert the effect of L-NAME returning the amplitude of naloxone-induced contracture to the same level in control morphine-dependent ilea. We also demonstrated that the competitive NMDA receptor antagonist DL-2-amino-5-phosphonovaleric acid (AP-5; 50 microM) potently reduced the amplitude of naloxone-induced contracture in the same model, an effect that was reversed by co-administration of the excitatory amino acid L-glutamate (40 microM). This in vitro study confirms the implication of the NO/NMDA pathways in morphine dependence.     

The effects of the selective kappa-opioid agonist MR 2034 on the guinea-pig ileum

The effects of the selective kappa-opioid agonist MR 2034 on the guinea-pig ileum were compared with those produced by the mu-agonist morphine. MR 2034 induced acute tolerance and inhibited electrically evoked contractions to the same extent as morphine. The slope of the concentration-effect curve to MR 2034 was not significantly different from that of morphine. However, MR 2034 and morphine may act at their respective receptors since naloxone was 6.57 times more effective at inhibiting responses to morphine than MR 2034. MR 2034, like morphine, induced acute dependence as revealed by naloxone-induced contractions of tissues that had been incubated with MR 2034 for 5 h. The functional properties of kappa-opoid receptors are the same as mu-receptors in the guinea-pig ileum.     

Pharmacological action ofPanax Ginseng on the behavioral toxicities induced by psychotropic agents

Morphine-induced analgesia has been shown to be antagonized by ginseng total saponins (GTS), which also inhibit the development of analgesic tolerance to and physical dependence on morphine. GTS is involved in both of these processes by inhibiting morphine-6-dehydrogenase, which catalyzes the synthesis of morphinone from morphine, and by increasing the level of hepatic glutathione, which participates in the toxicity response. Thus, the dual actions of ginseng are associated with the detoxification of morphine. In addition, the inhibitory or facilitated effects of GTS on electrically evoked contractions in guinea pig ileum (mu-receptors) and mouse vas deferens (delta-receptors) are not mediated through opioid receptors, suggesting the involvement of non-opioid mechanisms. GTS also attenuates hyperactivity, reverse tolerance (behavioral sensitization), and conditioned place preference induced by psychotropic agents, such as methamphetamine, cocaine, and morphine. These effects of GTS may be attributed to complex pharmacological actions between dopamine receptors and a serotonergic/adenosine A2A/ delta-opioid receptor complex. Ginsenosides also attenuate the morphine-induced cAMP signaling pathway. Together, the results suggest that GTS may be useful in the prevention and therapy of the behavioral side effects induced by psychotropic agents.     

Some pharmacological characteristics of the guinea pig ileum opioid system activated by cholecystokinin.

Naloxone, added after contractions induced by CCK-8 on the guinea pig ileum preparation, elicited a contraction attributed to the release of endogenous opioid which could inhibit the excitatory action of the peptide. With large concentrations of CCK-8, the preparation gave reproducible responses with time. Naloxone, added before the peptide, protracted the excitatory response to CCK-8, but not its height. Morphine decreased the response to CCK-8 but simultaneously raised the response to naloxone. The latter effect appeared very similar to the withdrawal contraction observed after brief exposure of the opioid in the guinea pig ileum to opioids. Clonidine, and alpha-2 adrenoceptor agonist, and nifedipine, a calcium channel antagonist, both known to interfere with tolerance and physical dependence, affected the excitatory response to CCK-8 and the subsequent response to naloxone in a different way.     

胍丁胺体外抑制豚鼠回肠的吗啡耐受和依赖

AIM: To observe effect of agmatine (Agm) on tolerance to and substance dependence on morphine (Mor) in guinea pig ileum longitudinal muscle (GPILM). METHODS: The experiment was performed in electric field stimulation (EFS) test in vitro. RESULTS: Mor inhibited twitch contractions of GPILM induced by EFS [IC50 = 140 (107-182) nmol.L-1]. Incubation of GPILM with Mor 270 nmol.L-1 for 8 h evoked a 37-fold increase in IC50 of Mor (tolerance) and a contractile response to naloxone (Nal, substance dependence). When the preparations were coincubated with Mor + Nal and Mor + Agm, Mor lost the ability to induce tolerance and inhibited the contractile responses of the preparations to Nal by 90% and 75%, respectively. These effects of Agm could be almost completely antagonized by idazoxan. CONCLUSION: Agm prevented the development of tolerance to and substance dependence on Mor in GPILM in vitro by activation of imidazoline receptors.     

Substance P and opioid interaction on stimulated and non-stimulated guinea pig ileum

In the past, substance P (SP) has been suggested to be both an opiate agonist and an antagonist. It therefore seemed appropriate to examine potential interactions of SP and opioids on guinea pig ileum. On non-stimulated ileal strips SP caused a dose responsive increase in contraction. Pretreatment of the tissue with morphine (3, 30, 300, 3000 nM), enkephalin (1.42, 14.2, 142, 1420 nM), naloxone (5 nM), or atropine (0.144 μM) did not significantly alter the spasmogenic effect of SP. On stimulated guinea pig ileum, whereas morphine and enkephalin inhibited the electrically induced twitch, SP administration resulted in contraction of the tissue. Additionally, neither strongly effective nor sub-threshold doses of SP antagonized the effects of the narcotics. These data are discussed in terms of separate receptors mediating the effects of the opiates and SP on guinea pig ileum.     

Cerebral extract from morphine-tolerant rats shows antiopiate properties in guinea pig ileum bioassay

The existence of an endogenous antiopiate system which counteracts endogenous opiate effects has been proposed. The present study set out to seek substance/s with morphine-antagonist activity in the brain and serum of morphine-tolerant rats. Cerebral extracts were partly purified on Sephadex G 25 and serum was ultrafiltered through membranes with pore diameter smaller than 0.005 micron. On the guinea pig ileum myenteric plexus longitudinal muscle a fraction of the cerebral extract and the serum ultrafiltrate in toto did increase electrically induced contractions, and antagonized the depressant effect of morphine. The serum ultrafiltrate also enhanced longitudinal smooth muscle tone. Preliminary findings suggest that levels of endogenous morphine-antagonist substance/s are higher in morphine-tolerant rats than in controls. Only cerebral extract, not serum ultrafiltrate, inhibited [3H]-naloxone binding to cerebral opiate receptors. In the guinea pig bioassay both the cerebral extract and serum ultrafiltrate antagonized, to some extent, the inhibition elicited by morphine, norepinephrine and adenosine. These observations support the existence of endogenous compound/s which may be functional antagonist/s of opiates and play a role in the development of tolerance and dependence.     

Experimental Models of Opiate Tolerance and Dependence

Abstract: Since observations in whole animals provide only limited information on the mechanisms underlying tolerance and dependence, less complex isolated tissue, cell culture and single neurone models have been developed, the most widely exploited of which is the guinea pig ileum. Prolonged exposure to morphine leads to tolerance to its acute inhibitory effects. Dependence is indicated by neuronal hyperexcitability when morphine is withdrawn or abruptly displaced from its receptor by naloxone. The mechanism of withdrawal hyperexcitability may be relatively non-selective since responses of both central and peripheral neurones to a variety of excitants are enhanced. Behavioural and biochemical experiments implicate elevated neuronal calcium and adenylate cyclase in the expression of dependence. However the relationship between these observations and the hyperexcitability of single neurones has not been rigorously examined. Moreover the relevance of an analysis of tolerance and physical dependence in experimental models to opioid reward mechanisms is uncertain. Although recent evidence suggests the importance of the ventral tegmental area in the rewarding actions of opiates, the biochemical and electrophysiological effects of exogenous opiates and of endogenous opioids on these neurones remain largely unexplored.     

甲氧氯普胺对吗啡依赖性的影响

目的:观察甲氧氯普胺对离体豚鼠回肠吗啡戒断收缩和吗啡精神依赖性的影响。方法:离休豚鼠回肠吗啡戒断收缩实验和吗啡诱导小鼠位置偏爱实验。结果:(1)离休豚鼠回肠吗啡依赖实验显示:250-500μmol·L~(-1)甲氧氯普胺可显著抑制离体豚鼠回肠吗啡依赖的形成和纳洛酮促发的戒断收缩,作用呈剂量依赖性;(2)甲氧氯普胺的剂量大于10(10-40)mg·kg~(-1)(ip),可有效抑制吗啡诱导的小鼠条件性位置偏爱的形成,而其本身并不造成位置厌恶。结论:甲氧氯普胺对吗啡身体依赖的形成、戒断症状以及精神依赖的形成均有一定的抑制作用。     

Development of narcotic tolerance and physical dependence: effects of Pro-Leu-Gly-NH2 and cyclo (Leu-Gly)

Administration of Pro-Leu-Gly-NH2 (MIF) and cyclo (Leu-Gly) blocked the development of tolerance to and physical dependence on morphine, induced by the pellet implanation procedure in mice. Inhibition of tolerance development by peptides was evidenced by the presence of an analgesic response (increase in jump threshold) as determined by measuring the jump threshold to an increasing electric current, after a challenge dose of morphine (40 mg/kg). The same dose of morphine did not alter the jump threshold in morphine tolerant mice which were injected with saline prior to pellet implantation. The inhibition of the development of physical dependence on morphine by these peptides was evidenced by the antagonism of the hypothermic response which occurs during abrupt or naloxone-induced withdrawal. The naloxone-induced withdrawal jumping response was unaffected by these peptides. Dose-response experiments indicated that cyclo (leu-Gly) was much more potent than MIF in these tests. These peptides, when given after the development of tolerance and dependence, did not modify either the analgesic response to morphine or the symptoms of abrupt and naloxone-precipitated withdrawal. The inhibition of development of analgesic tolerance and physical dependence was not associated with changes in brain morphine concentration. The data indicate that these peptides do not interfere withe the morphine-morphine receptor complex formation but alter a subsequent step in the genesis of some aspects of tolerance and dependence processes.     

The effect of isoquinoline alkaloids on opiate withdrawal

Our interest has been centered on isoquinoline alkaloids obtained from Argemone mexicana (Papaveraceae), Aristolochia constricta (Aristolochiaceae) and the opium alkaloid, papaverine. In this respect, the effect of these isoquinoline alkaloids was investigated on contractions induced by naloxone of isolated guinea pig ileum acutely exposed to morphine in vitro. The activity of these alkaloids was compared to the control compound, papaverine. Furthermore, the effect of these isoquinoline alkaloids was also determined on naloxone-precipitated withdrawal in isolated guinea pig ileum exposed to DAMGO (highly selective mu opioid receptor agonist) and U50-488H (highly selective kappa opioid receptor agonist) to test whether the possible interaction of isoquinoline alkaloids on opioid withdrawal involves mu- and/or kappa-opioid receptors. Isoquinoline alkaloids from A. mexicana (from 5 x 10(-6) to 1 x 10(-4) M), from A. constricta (1 x 10(-5) x 10(-5)-1 x 10(-4) M) as well as papaverine treatment (1 x 10(-7)-5 x 10(-6)-1 x 10(-6) M) before or after the opioid agonists were able of both preventing and reversing the naloxone-induced contraction after exposure to mu (morphine and DAMGO) or kappa (U50-488H) opiate receptor agonists in a concentration-dependent manner. Both acetylcholine response and electrical stimulation were also reduced by isoquinoline alkaloids and papaverine treatment as well as the final opiate withdrawal was still reduced. The results of the present study indicate that isoquinoline alkaloids as well as papaverine were able to produce significant influence on the opiate withdrawal in vitro and these compounds were able to exert their effects both at mu and kappa opioid agonists.     

Further studies on the effects of disodium cromoglycate on guinea pig ileum

Transmural electrical stimulation was carried out on innervated strips of the longitudinal muscle of guinea pig ileum. Disodium cromoglycate (DSCG) inhibited the electrically induced contractions. Five minutes later, prostaglandin E2 (2.5 ng/ml) was added to the bath and it reversed the action of DSCG. Furthermore, DSCG inhibits significantly the guinea pig ileum contractions induced by nicotine and also those induced by histamine and acetylcholine on ileum denervated by cooling. These results suggest that DSCG effects on guinea pig ileum contraction are mediated by membrane-stabilizing properties of this drug on smooth muscle fibres as well as on myenteric plexus.     

NO对去甲吗啡在离体豚鼠回肠上依赖性耐受性产生的作用

目的观察 ＮＯ合酶（ ＮＯ ｓｙｎｔｈａｓｅ,ＮＯＳ）抑制剂左旋硝基精氨酸（ＮＧ－ｎｉｔｒｏ－Ｌ－ａｒｇｉｎｉｎｅ,ＮＯＡｒｇ）和 ＮＯ合成前体左旋精氨酸（Ｌ－ａｒｇｉｎｉｎｅ,Ｌ－Ａｒｇ）对去甲吗啡（ｎｏｒｍｏｒｐｈｉｎｅ,ＮＭ）在离体豚鼠回肠上依赖性耐受性产生的影响,研究ＮＯ在阿片类药物依赖性耐受性产生中的作用。方法以离休豚鼠回肠为实验对象,４℃孵育６ ｈ, ２４ ｈ后,分别测定纳洛酮（ｎａｌｏｘｏｎｅ,Ｎｘ）与氯化乙酰胆碱（ａｃｅｔｙｌｃｈｏｌｉｎｅ,Ａｃｈ）引起的收缩高度比值,作为依赖性产生的指标。在耐受性产生实验中,分别测定回肠空白组和药物组４℃孵育３ｈ后对ＮＭ抑制电刺激收缩的剂量反应曲线。结果回肠分别经ＮＭ,ＮＭ加ＮＯＡｒｇ,ＮＭ加Ｌ－Ａｒｇ中孵育６ｈ后,纳洛酮均可使其产生戒断收缩,且两组与Ａｃｈ的收缩高度比值差异无显著性（ｎ＝６）, Ｐ＞０．０５。而孵育２４ ｈ后,ＮＭ,ＮＭ加 Ｌ－Ａｒｇ组收缩高度比值分别为 ０． ８９±０． ０２, ０． ９０±０． ０２, Ｐ＞ ０． ０５,而ＮＭ加ＮＯＡｒｇ药物组对纳洛酮的戒断收缩反应明显减弱,收缩高度比值为 ０．４７± ０．０５（ｎ＝ ６, Ｐ＜ ０．０１）。可见ＮＭ加ＮＯＡ?     

Morphine-theophylline interaction: antagonism or facilitation?

1 Morphine-theophylline interactions were investigated in both acute and narcotic-dependent preparations, in vitro and in vivo, using four different experimental models: LD50 doses of morphine and naloxone in the mouse; naloxone-induced contractions in the electrically-stimulated and opiate-dependent isolated ileum of the guinea-pig; naloxone-induced jumps in the mouse; an calcium uptake in synaptosomal preparations. 2 The LD50 of morphine was significantly increased by theophylline. 3 The lethal effect of theophylline was potentiated by pretreatment of the animals with naloxone. 4 Theophylline displayed protective effects in the inhibitory response to morphine and antagonism to the withdrawal response induced by naloxone in the electrically-stimulated isolated ileum of the guinea-pig. 5 The number of jumps induced by naloxone in morphine-dependent mice was significantly diminished by theophylline. 6 The inhibitory effect of morphine on the synaptosomal uptake of calcium was decreased by theophylline. 7 The effects of both morphine and theophylline on the cyclic nucleotides and the possible role of calcium in these actions are discussed.     

戒毒康对吗啡依赖豚鼠离体回肠戒断性收缩的影响

目的研究戒毒康对吗啡依赖豚鼠离体回肠催促戒断反应的抑制作用。方法连续递增皮下注射吗啡,建立豚鼠身体依赖性模型,利用MD2000 Super Lab生物信息采集系统观察戒毒康对纳洛酮催促诱发吗啡身体依赖性豚鼠离体回肠的戒断性收缩的抑制作用。结果戒毒康高（0.6 mg.mL-1）、中（0.3 mg.mL-1）、低（0.15 mg.mL-1）3个剂量对吗啡依赖豚鼠离体回肠纳洛酮催促戒断性收缩的抑制率分别为：78.8%,46.8%,30.0%,并呈剂量相关性,其中高剂量组和中剂量组与模型组比较,有显著性差异。结论戒毒康在一定程度上能抑制吗啡依赖豚鼠离体回肠体外纳洛酮催促戒断性收缩。     

Conformationally restricted analogs of histamine H1 receptor antagonists: trans and cis-1-benzyl-3-dimethylamino-6-phenylpiperidine.

The syntheses of trans- and cis-1-benzyl-3-dimethylamino-6-phenylpiperidine (1 and 2) are described. Compounds 1 and 2 were found to be inhibitors to histamine, acetylcholine, and barium chloride induced contractions of the isolated guinea pig ileum. Compounds 1 and 2 do not exhibit appreciable stereoselectivity in their ability to inhibit smooth muscle contractions. The cis compound 2 is a more effective inhibitor of histamine N-methyltransferase than the trans isomer 1.     

Attenuation of morphine tolerance and dependence by aminoguanidine in mice

The effect of aminoguanidine, an inducible nitric oxide synthase (iNOS) inhibitor, on morphine-induced tolerance and dependence in mice was investigated in this study. Acute administration of aminoguanidine (20 mg/kg, p.o.) did not affect the antinociceptive effect of morphine (10 mg/kg, s.c.) as measured by the hot plate test. Repeated administration of aminoguanidine along with morphine attenuated the development of tolerance to the antinociceptive effect of morphine. Also, the development of morphine dependence as assessed by naloxone-precipitated withdrawal manifestations was reduced by co-administration of aminoguanidine. The effect of aminoguanidine on naloxone-precipitated withdrawal was enhanced by concurrent administration of the non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist, dizocilpine (0.25 mg/kg, i.p.) or the non-specific nitric oxide synthase (NOS) inhibitor, l-N(G)-nitroarginine methyl ester (l-NAME; 5 mg/kg, i.p.) and antagonized by concurrent administration of the nitric oxide (NO) precursor, l-arginine (50 mg/kg, p.o.). Concomitantly, the progressive increase in NO production, but not in brain glutamate level, induced by morphine was inhibited by repeated administration of aminoguanidine along with morphine. Similarly, co-administration of aminoguanidine inhibited naloxone-induced NO overproduction, but it did not inhibit naloxone-induced elevation of brain glutamate level in morphine-dependent mice. The effect of aminoguanidine on naloxone-induced NO overproduction was potentiated by concurrent administration of dizocilpine or l-NAME and antagonized by concurrent administration of l-arginine. These results provide evidence that blockade of NO overproduction, the consequence of NMDA receptor activation, by aminoguanidine, via inhibition of iNOS, can attenuate the development of morphine tolerance and dependence.     

Effects of endotoxin-induced shock on withdrawal contractions in the Guinea-pig isolated ileum

1. Taking into consideration the effect of septic shock on releasing various mediators, the present study was undertaken in an attempt to elucidate the effect of endotoxin on naloxone-induced withdrawal contractions in the guinea-pig isolated ileum. 2. To induce withdrawal contractions, preparations removed either from saline- or endotoxin (2.5 mg/kg in 0.4 mL, i.p.)-treated animals were incubated for 5 min with morphine (40 micromol/L) and naloxone (50 micromol/L) was then applied. 3. In tissues removed from endotoxin-treated animals, a significant reduction in withdrawal contractions was observed. In control preparations, indomethacin (1 micromol/L for 15 min) significantly reduced naloxone-induced contractions, whereas N(G)-nitro-L-arginine methyl ester (L-NAME; 10 micromol/L for 15 min) had no effect. However, indomethacin pretreatment of tissues removed from endotoxin-treated animals did not modify the withdrawal contractions, whereas L-NAME pretreatment enhanced the amplitude of the withdrawal-induced contractions. 4. These results suggest that attenuation of the withdrawal contractions in guinea-pig isolated ileum induced by endotoxin-pretreatment may be due, in part, to the activation of an L-arginine-nitric oxide pathway.