吗啡对淋巴细胞反应性的影响

本文探讨小鼠或大鼠一次性sc吗啡对分裂原诱导的淋巴细胞增殖反应的影响。结果,吗啡抑制Con A诱导的小鼠或大鼠全血淋巴细胞增殖反应,作用呈浓度依赖关系;但脾淋巴细胞反应性并未明显受损,即使吗啡给药浓度增至50 mg·kg~(-1)。如分离大鼠全血单个核细胞,再观察其对Con A的反应性,则吗啡的抑制活性依然存在,提示全血中的血浆成分不是全血和脾淋巴细胞对吗啡作用敏感性不同的原因。进一步实验发现,纳洛酮10 mg·kg~(-1)预处理可完全拮抗吗啡25 mg·kg~(-1)所致小鼠和大鼠全血淋巴细胞反应性下降,使其恢复至正常水平;而单独给予纳洛酮,对脾和全血淋巴细胞增殖皆无影响。结果表明,吗啡整体给药的免疫调节作用与药物剂量及淋巴细胞的组织来源有关,且其效应通过阿片受体介导。     

Nifedipine suppresses morphine-induced thermal hyperalgesia: evidence for the role of corticosterone

It has been shown that systemic administration of morphine induced a hyperalgesic response at an extremely low dose. We have examined the effect of nifedipine, as a calcium channel blocker, on morphine-induced hyperalgesia in intact and adrenalectomized rats and on hypothalamic-pituitary-adrenal axis activity induced by ultra-low dose of morphine. To determine the effect of nifedipine on hyperalgesic effect of morphine, nifedipine (2 mg/kg i.p. and 10 microg i.t.) that had no nociceptive effect, was injected concomitant with morphine (1 microg/kg i.p. and 0.01 microg i.t. respectively). The tail-flick test was used to assess the nociceptive threshold, before and 30, 60, 120, 180, 240 and 300 min after drug administration. The data showed that low dose morphine systemic administration could produce hyperalgesic effect in adrenalectomized rats equivalent to sham-operated animals while intrathecal injection of morphine only elicited hyperalgesia in sham-operated animals. Nifedipine could block morphine-induced hyperalgesia in sham and adrenalectomized rats and even a mild analgesic effect was observed in the adrenalectomized group which was reversed by corticosterone replacement. Systemic administration of low dose morphine produced significant increase in plasma level of corticosterone. Nifedipine has an inhibitory effect on morphine-induced corticosterone secretion. Thus, the data indicate that dihydropyridine calcium channels are involved in ultra-low dose morphine-induced hyperalgesia and that both the pattern of morphine hyperalgesia and the blockage of it by nifedipine are modulated by manipulation of the hypothalamic pituitary adrenal axis.     

Role of nitric oxide in catalepsy and hyperthermia in morphine-dependent rats

The possible involvement of nitric oxide (NO) in morphine-induced catalepsy and hyperthermia was studied in morphine-dependent rats. Four days repeated injection regimen was used to induce morphine dependence, which was assessed by naloxone challenge (0.5 mg x kg(-1), s.c.). Pretreatment of rats with the NO synthase inhibitor, N(G)-nitro-L-arginine (L-NA, 8 mg x kg(-1) twice daily, i.p.) potentiated the cataleptic response of morphine as shown by a rightward shift in the morphine-log dose-response curve. Prior treatment of rats with the NO precursor, L-arginine (200 mg x kg(-1), twice daily, i.p.) abolished the potent effect of L-NA and restored the cataleptic scores to levels similar to those of morphine-dependent rats. The same dose of L-NA significantly blocked morphine-induced hyperthermia at the dose levels of morphine (15-105 mg x kg(-1)) and this effect was reversed by L-arginine. These data provide the first experimental evidence that NO is involved in morphine induced catalepsy and hyperthermia and demonstrated that blockade of NO synthesis may suggest a dangerous interaction with opioids in the control of motor function.     

MODIFICATION BY GABA-ERGIC AGENTS AND CLONIDINE OF MORPHINE-INDUCED CONVULSIONS AND TOXICITY IN RATS

1. Intracerebroventricular (i.c.v.) administration of morphine produced dose-dependent behavioural changes in rats, the highest dose producing violent tonic convulsions. 2. Naloxone (up to 10 mg/kg i.p., or 100 μg i.c.v.) failed to reverse morphine-induced toxicity. 3. The conventional anticonvulsant drugs also failed to offer protection to morphine-induced seizures. 4. GABA-ergic substances, GABA, piracetam and diazepam, on the other hand, protected the animals against morphine-induced convulsions and toxicity. Similarly, clonidine pretreatment also had a protective action against morphine-induced convulsions.     

Increased brain uptake of morphine in the presence of the antihistamine tripelennamine

Disposition of [6 3H (N)]morphine in plasma, brain and liver of rats was studied 15 min after intravenous injection of either a 2 mg kg-1 dose of morphine or a combination of the same dose of morphine with a 6 mg kg-1 dose of tripelennamine. The concentrations of morphine in brain and the brain to plasma morphine ratios in animals receiving the combination of drugs concurrently were significantly higher than those in the control morphine group. No significant differences were seen in the morphine or morphine metabolite concentrations in plasma and liver or liver to plasma morphine concentration ratios in the 2 groups. Data suggest that pharmacokinetic factors play a role in the potentiation of opiate effects by antihistamine on concurrent i.v. administration of the two drugs.     

Time course of verapamil interaction with morphine effects on physiological parameters in rats

The effects of subcutaneous doses of morphine and verapamil on respiratory and cardiovascular parameters have been assessed in conscious rats. Verapamil (10 mg kg-1) was injected simultaneously with morphine (16 mg kg-1) or at 10, 30, or 60 min before morphine administration. Morphine induced respiratory depression, as indicated by marked hypercapnia, hypoxia and acidosis, and caused marked tachycardia. Although morphine produced only a minor and inconsistent (but statistically significant, P less than 0.01) reduction of mean arterial blood pressure, morphine potentiated verapamil-induced hypotension. Verapamil suppressed morphine-induced hypercapnia only when injected simultaneously with morphine. Verapamil alone did not affect arterial blood gases or pH, but decreased heart rate and mean arterial blood pressure. Verapamil attenuated and delayed the maximum positive chronotropic effects of morphine at all times tested. Antagonism by verapamil of respiratory depression and tachycardia produced by morphine was unrelated to morphine levels in plasma. Thus, the explanation of verapamil-morphine interactions on respiration and cardiovascular function is not pharmacokinetic.     

Role of the NO/sGC/PKG signaling pathway of hippocampal CA1 in morphine-induced reward memory

Although evidence suggests that the nitric oxide(NO)/soluble guanylyl cyclase(sGC)/cGMP dependent protein kinase(PKG) signaling pathway in the hippocampal CA1 region plays a key role in memory processing,it remains unclear whether this signaling cascade is involved in drug-induced reward memory.In this study,we investigated the role of the NO/sGC/PKG signaling pathway in the CA1 on morphine-induced reward memory using a conditioned place preference(CPP) paradigm.We found that rats receiving an intraperitoneal(ip) injection of 4 mg·kg-1 morphine exhibited CPP,whereas rats treated with only 0.2 mg·kg-1 morphine failed to produce CPP.Intra-CA1 injection of the neuronal NO synthase(nNOS) inhibitor 7-NI,the sGC inhibitor ODQ or the PKG inhibitor Rp-8-Br-PET-cGMPS had no effect on the acquisition of CPP by 4 mg·kg-1 morphine.Intra-CA1 injection of 7-NI blocked the consolidation of CPP induced by 4 mg·kg-1 morphine,and this amnesic effect of 7-NI was mimicked by ODQ and Rp-8-Br-PET-cGMPS.Intra-CA1 injection of the NOS substrate L-arg or the sGC activator YC-1 with an ineffective dose of morphine(2 mg·kg-1,ip) elicited CPP.This response induced by L-arg or YC-1 was reversed by pre-microinjection of Rp-8-Br-PET-cGMPS in the CA1.These results indicated that the activation of the NO/sGC/PKG signaling pathway in the CA1 is necessary for the consolidation of morphine-related memory.     

Morphine 6-glucuronide: a metabolite of morphine with greater emetic potency than morphine in the ferret.

1. The emetic potencies of morphine and its metabolite morphine 6-glucuronide have been determined in the ferret by constructing dose-response curves for mean total retches and vomits for subcutaneous doses of 0.05 mg kg-1 to 5 mg kg-1. Morphine 6-glucuronide induced retching and vomiting at lower doses than morphine and at a maximal dose induced more retching and vomiting than morphine. 2. The emesis induced by both morphine and morphine 6-glucuronide was abolished by the preadministration of naloxone (0.5 mg kg-1 s.c.). 3. The 5-HT3 receptor antagonists granisetron and ondansetron (1 mg kg-1, s.c.) failed to abolish or reduce emesis induced by either compound. 4. At a high-dose (5 mg kg-1), morphine but not morphine 6-glucuronide failed to induce emesis and abolished the emesis induced by the cytotoxic drug, cyclophosphamide (200 mg kg-1, i.p.). 5. Preliminary pharmacokinetic studies of intravenous and subcutaneous morphine and morphine 6-glucuronide revealed that morphine 6-glucuronide accounts for less than 1% of the metabolic product of morphine in the ferret. Peak plasma levels of the two compounds after their subcutaneous administration were obtained within 10 min. The metabolic profile of morphine was not dose-dependent. There was no relationship between plasma level and emetic response for either compound.     

Plasma corticosterone responses to stress following chronic oral administration of diazepam in the rat.

The effect of daily, oral administration of diazepam on plasma corticosterone responses to stressors of varying intensity was investigated. In rats exposed to the mild stress of noise, diazepam, 10 mg kg-1 but not 1.0 or 0.1 mg kg-1, reduced plasma corticosterone concentrations by 30% in comparison with controls. However, in rats exposed to the more severe stressors, foot-shock or immobilization, none of these doses of diazepam reduced plasma corticosterone responses. In unstressed rats, diazepam 10 mg kg-1 raised plasma corticosterone concentrations. It is suggested that plasma corticosterone concentrations are not a reliable indicator of the tranquillizing effect of diazepam during stress.     

川芎嗪可抑制吗啡戒断大鼠的血压及血清单胺类递质升高

目的··:观察川芎嗪对吗啡戒断大鼠高血压的抑制及血清单胺类递质的影响。方法··:采用剂量递增的方法皮下注射吗啡 ,经纳洛酮催促戒断建立吗啡戒断大鼠模型,根据戒断反应中大鼠的平均动脉压(mABP)评定戒断大鼠血压水平。用分光光度计检测血中单胺类递质的含量。结果··:3种不同剂量的川芎嗪组mABP与生理盐水组比较 ,显著下降 (P<0.05,P<0.01) ,与戒断组比较 ,60mg·kg-1 川芎嗪组血中单胺类递质含量显著下降(P<0.01)。结论·· :川芎嗪可明显抑制吗啡戒断大鼠的血压升高 ,并抑制戒断反应引起的血清单胺类递质的升高。     

Developmental responses to opioids reveals a lack of effect on stress-induced corticosterone levels in neonatal rats.

The neonate has an unusual capacity for survival and the possibility exists that mechanisms for controlling stress responses may differ in the developing animal. In adults both endogenous and exogenous opioids can modulate the corticosterone responses to stress. We have studied this effect in neonatal rats and found that opioid modulation is absent in early postnatal development. Neonatal rats of either sex were injected with morphine (5-50 mg kg-1), fentanyl (10-100 micrograms kg-1), buprenorphine (0.1-30 mg kg-1) or naloxone (0.1-10 mg kg-1) and plasma corticosterone measured fluorimetrically 15 or 20 min later. In addition naloxone reversibility studies (1 mg kg-1, co-administered) were carried out for the opioid agonists. In adult rats, elevations in plasma corticosterone caused by injection stress were potentiated by morphine, fentanyl and buprenorphine. In neonates, though injection stress-induced rises in plasma corticosterone were absent at 10 days, elevations were observed at 21 days and later. However, significant potentiation of this corticosterone response by fentanyl was absent at 21 days and at later ages (30 and 40 days) for morphine and buprenorphine. The potentiating effect of all three agonists did not become fully effective until day 45. In addition, in animals acclimatized to injection stress by 7 day injection pretreatment, fentanyl did not significantly alter corticosterone levels in 30 day old neonates. High doses of naloxone (10 mg kg-1) significantly increased the corticosterone response to injection stress in adult rats but this effect was absent in 30 day old animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Studies to determine whether there is tolerance or cross-tolerance to the antisecretory effect of morphine and clonidine in the rat intestine.

Intra-arterial infusions (4 micrograms min-1) of prostaglandin E2 (PGE2) were used to stimulate intestinal fluid secretion in anaesthetized rats. Morphine (0.625-40 mg kg-1) produced a dose-dependent restoration of fluid transport from secretion to the normal rate of absorption. Pretreatment with up to eight doses of morphine (20 mg kg-1) did not induce tolerance, rather it enhanced the antisecretory effect of a subsequent acute dose of morphine. It seems probable that this was caused by the accumulation of morphine in the intestine. Clonidine (4-1000 micrograms kg-1, like morphine, produced a dose-dependent reversal of stimulated fluid secretion. Pretreatment with clonidine (4 x 0.25 mg kg-1) caused a shift of the clonidine antisecretory dose-response curve to the right, demonstrating tolerance. Pretreatment with clonidine also caused cross-tolerance to the antisecretory effect of morphine. The results suggest that there is a close relationship between opioid- and alpha 2-adrenoceptors in controlling inhibition of intestinal fluid secretion.     

Biphasic dose-related effects of morphine on dopamine release.

The effects of morphine on extracellular dopamine levels in brain have never been studied over a wide range of doses within a single study. This has made it difficult to make definitive interpretations of drug interactions with morphine. An inhibition of morphine-induced increases in dopamine could be interpreted as either antagonism or potentiation depending the shape of the morphine dose-response curve. Accordingly, the aim of the present study was to determine the effects of a wide range of morphine doses (0, 5, 10, 20 and 30 mg/kg, i.p.) on extracellular dopamine, DOPAC and HVA levels in the nucleus accumbens and striatum of awake and freely moving female Sprague-Dawley rats. The results show that, in both brain regions, the dose-response curve for morphine-induced increases in dopamine is non-monotonic while the dose-response curve for morphine-induced increases in DOPAC and HVA is monotonic in the nucleus accumbens. The results of this study are discussed in terms of their implications for interpreting drug interactions with morphine and with relationship to morphine's mode of action at mu and kappa opioid receptors.     

Effect of histamine and stress on the gastric mucosal Ca2+ content during the development of gastric ulcers.

The influence of histamine, its triazole derivative (3-beta-aminoethyl-1,2,4-triazole) and immobilization stress on the gastric mucosal Ca2+ content during the development of gastric ulcers in guinea pigs and rats was investigated. A considerable fall in the concentration of Ca2+ in gastric tissues of guinea pigs after administration of histamine 0.25 mg/kg, down to 80% (8.0 mumol/g), its derivative (1 mg/kg) to 72% (7.2 mucol/g) and stress to 76% (7.6 mumol/g) was recorded by atomic absorption-spectrophotometric techniques, while the calcium level in the controls stood at 9.9 mumole/g. Similar changes (90-65%) were seen in the blood plasma. In rats, the Ca2+-decreasing effects of stress ran closely parallel with increasing ulceration, and depended on the duration of stress. The immobilization of rats evoked a slight rise in the Na+ content of the gastric tissues. After 4 h immobilization, the tissue concentration of Na+ was increased to 116% of control levels. Cimetidine (100 mumol kg-1 more than 50% inhibited the development of gastric ulcers and prevented the change in Ca2+ concentration ions. Thus, the data suggest that Ca2+ ions take part not only in the regulation of secretion, but also in stress tissue dystrophy.     

孕酮对吗啡精神依赖大鼠海马和纹状体中阿片受体水平的影响

目的观察孕酮对于吗啡所致奖赏效应及海马和纹状体μ受体水平的影响。方法32只SD大鼠随机分为空白对照组、吗啡组、孕酮组和孕酮加吗啡组,并建立吗啡条件性位置偏爱(CPP)模型,采用免疫组化法测定大鼠海马和纹状体中μ受体的水平。结果与空白对照组比较,5 mg.kg-1吗啡可诱导大鼠产生稳定的CPP效应(P<0.01),15 mg.kg-1孕酮本身不产生CPP效应,但能抑制吗啡的CPP效应。与空白对照组比较,吗啡CPP形成时,海马和纹状体中μ受体的数量降低(均为P<0.01)。与吗啡组比较,合用15 mg.kg-1孕酮可使纹状体中μ受体的数量升高(P<0.05),而在海马中未见变化。结论孕酮可以有效抑制吗啡CPP效应,其机制可能与其逆转吗啡诱导的纹状体中μ受体水平的变化有关。     

促甲状腺激素释放激素对大鼠内毒素性休克的影响

研究了不同剂量TRH(促甲状腺激素释放激素)对大鼠大肠杆菌内毒素性休克的影响,并与纳洛酮进行比较.发现低(0.22mg·kg~(-1),iv)、中(0.67mg·kg~(-1),iv)、高(2mg·kg~(-1),iv)剂量的TRH均能迅速纠正内毒素性低血压,且明显提高大鼠24h存活率.2mg·kg~(-1)纳洛酮的升压效应与低剂量TRH相当,但前者在较低血压水平上提高大鼠存活率的作用更强,此点与TRH不同.     

Investigation of the central sites at which morphine acts to cause hypertension in conscious rabbits.

1. In conscious rabbits intracerebroventricular (i.c.v.) morphine (10 and 50 micrograms kg-1) caused a dose-related increase in plasma noradrenaline and adrenaline, respiratory depression and sedation. The increase in sympatho-adrenal outflow resulted in hypertension accompanied by bradycardia and the increase in adrenaline secretion caused hyperglycaemia. Morphine (1 microgram kg-1 i.c.v.) and i.c.v. saline had no effect. 2. The same doses of morphine given intracisternally (i.c.) caused bradycardia and a similar degree of respiratory depression to i.c.v. morphine, but no significant increase in blood pressure and only a small, gradual rise in plasma adrenaline. 3. Intravenous naloxone (1 mg kg-1) did not block the hypertension, hyperglycaemia or increase in plasma catecholamines that followed i.c.v. morphine, but prevented the respiratory depression and sedation. 4. Ganglionic blockade with pentolinium prevented the rise in plasma catecholamines, blood pressure and plasma glucose induced by i.c.v. morphine. 5. These findings demonstrate that the increased sympathoadrenal outflow following i.c.v. morphine results from an action on periventricular structures. The resultant increase in plasma catecholamines, which is largely naloxone resistant, accounts for the hypertension and hyperglycaemia. The bradycardia is probably partly baroflex mediated and partly due to an increase in vagal tone as a result of stimulation of brainstem opioid receptors. The respiratory depression is probably due to an action of morphine on brainstem opioid receptors.     

The effects of granisetron, ICS 205-930 and ondansetron on the visceral pain reflex induced by duodenal distension.

1. Distension of the duodenum in anaesthetized rats, by rapid application of intraluminal pressures (10-75 cmH2O), evoked falls in diastolic blood pressure and intragastric pressure. 2. The distension-induced responses were blocked by pretreatment with morphine (20 mg kg-1, s.c.), an action reversible by injection of naloxone (5 mg kg-1, i.v.). 3. Bilateral cervical vagotomy reduced the distension-evoked fall in intragastric pressure but had no effect on the corresponding fall in blood pressure. 4. Granisetron or ICS 205-930 (1-1000 micrograms kg-1, i.v.) had no effects on duodenal intraluminal pressure, but reduced the responses to distension with a bell-shaped dose-response relationship. Ondansetron (1-1000 micrograms kg-1, i.v.) did not reduce the reflex responses. 5. These results show that the 5-HT3 receptor antagonists used exerted different effects on the reflex responses to duodenal distension.     

Ontogenesis of morphine-induced behavior in the rat

Ten, seventeen and twenty-four day old rats were observed using a behavioral-time sampling procedure following injection of saline, 0.1, 0.5, 1.0 or 5.0 mg/kg/5cc morphine sulphate. At Day 10, the predominant response to morphine was a depression of locomotor activity. At the 5 mg/kg dose, catalepsy was also seen. In animals of this age, 0.1 mg/kg morphine, which was not sufficient to depress activity, also had no effect on stereotyped gnawing/mouthing behavior, nor did it produce any increase in locomotor activity. A morphine-induced increase in locomotion was first seen on Day 17 (after 0.5 mg/kg morphine). As with Day 10 animals, Day 17 animals given 5 mg/kg morphine showed a depression of locomotion and catalepsy. Stereotypic gnawing/mouthing behavior was first seen in Day 24 animals (after 5 mg/kg morphine), although no dose of morphine produced significant differences in activity at this age. Possible mechanisms resulting in these marked alterations in behavioral response patterns to morphine during this two week period of ontogeny are discussed.     

Effect of methylguanidine on rat blood pressure: role of endothelial nitric oxide synthase.

1. The effect of acute i.v. administration of methylguanidine (MG) on mean arterial blood pressure (MABP) was investigated in anaesthetized male Wistar rats. 2. MG (1-30 mg kg-1 i.v.) produced an increase in MABP in a dose-dependent manner both in normal and in hexamethonium (5 mg kg-1, i.v)-treated rats. 3. L-Arginine (30 or 150 mg kg-1, i.v.), but not its enantiomer D-arginine (30 or 150 mg kg-1, i.v.), reversed the effect of MG on MABP in both normal and hexamethonium-treated rats. 4. L-Arginine (150 mg kg-1, i.v.) administered 2 min before MG (30 mg kg-1, i.v.) prevented the increase in MABP caused by MG in either normal or hexamethonium-treated rats. This effect was not observed with D-arginine (150 mg kg-1, i.v.). 5. Thus, the rise in MABP caused by MG in the anaesthetized rat is due to inhibition of endothelial NO-synthase activity. We speculate that the rise in the plasma concentration of endogenous MG associated with uraemia may contribute to the hypertension seen in patients with chronic renal failure.