吗啡对脑缺血再灌注损伤后神经元凋亡及Bcl-2的影响

目的:探讨吗啡预处理对大鼠脑缺血再灌注损伤后神经元凋亡及Bcl-2蛋白表达的影响.方法:Wistar大鼠随机分为假手术组、模型组、吗啡组,各18只.四动脉阻断法建立脑缺血模型,吗啡组在脑缺血前60 min腹腔内注射吗啡1mg/kg.脑缺血8 min再灌注12h、72h及168h各取6只大鼠的脑组织,观察海马区病理学改变、神经元凋亡及Bcl-2表达.结果:吗啡预处理能使各灌注点海马神经元病理改变减轻、凋亡细胞数减少(P<0.01)、Bel-2表达增加(P<0.01).吗啡组细胞凋亡数减少趋势与Bcl-2表达上调趋势一致.结论:吗啡预处理可减轻缺血性脑损伤;吗啡抗凋亡作用机制与Bcl-2密切相关.     

Loss of morphine hyperphagia following neonatal monosodium glutamate treatment in rats

Morphine stimulates food intake in mildly-deprived and nondeprived rats. Neonatal administration of monosodium glutamate (MSG) destroys the medial-basal hypothalamus and other circumventricular organs, including cells containing beta-endorphin that project to other hypothalamic nuclei proposed in the modulation of morphine hyperphagia. Food intake of MSG-treated and control rats were assessed following vehicle and morphine (1.0-5.0 mg/kg, sc) treatment in a mild (5h) food deprivation paradigm. Morphine hyperphagia was found to be absent in MSG-treated rats, although they responded normally to mild deprivation following vehicle treatment. These results add to the types of ingestive deficits observed in the MSG-treated rat, and suggest that the circumventricular system in general, and opioid medial-basal hypothalamic cells in particular may be implicated in morphine hyperphagia.     

Attenuation of morphine analgesia by lesions of the preoptic forebrain region in the rat.

Latency to tail withdrawal from hot water was measured as a pain response before and after morphine injection in female rats. Morphine increased the withdrawal latency. Lesions in the preoptic forebrain region attenuated morphine analgesia.     

脊髓水平iNOS在吗啡依赖大鼠戒断反应中的作用

目的:探讨脊髓水平诱导型一氧化氮合酶在吗啡依赖大鼠戒断反应中的作用。方法:健康雄性SD大鼠72只,体重200~250 g,吗啡剂量每次10 mg/kg,每日2次,隔日每次增加10 mg/kg,至第6天末次注射50 mg/kg,大鼠腹腔注射纳洛酮4 mg/kg建立吗啡依赖及戒断模型,在纳洛酮激发戒断前30 min鞘内注射iNOS特异性抑制剂氨基胍(AG)150μg。分为正常对照组、吗啡依赖组、吗啡戒断组、AG组。采用行为学(n=8)、免疫组织化学(n=6)和Western blot(n=4)方法观察鞘内应用iNOS特异性抑制剂氨基胍对吗啡依赖大鼠纳洛酮催促戒断反应和脊髓神经元iNOS表达的影响。结果:AG组戒断症状评分和戒断组促诱发痛评分均低于戒断组(P<0.05)。免疫组织化学和Western blot显示戒断组大鼠脊髓iNOS阳性神经元的数目和蛋白的表达增高,而AG组大鼠脊髓iNOS阳性神经元的数目和iNOS蛋白的表达低于戒断组(P<0.05)。结论:脊髓水平iNOS表达上调可能参与介导吗啡戒断反应。     

Protective effect of vilva juice on glycoconjugate levels in experimentally induced constipation in rats

Efficacy of vilva, a polyherbal formulation was evaluated in morphine induced constipated rats. Vilva juice, at a dose of 1.5 ml/100 g body wt was given orally for a period of 7 days. Morphine sulfate was injected to induce constipation on 8th day, 45 min before the experiments. Protein bound glycoconjungates were estimated in intestinal tissue. Altered levels of glycoconjugates were maintained at near normalcy when pretreated with vilva juice in morphine induced rats. Histological changes were observed in the colon tissue. The damage to crypts of Liberkunn in constipated rats were found to be reduced in vilva pretreated rats. Vilva, thus, offered significant protection against morphine induced constipation by way of augmenting mucus secretion.     

Development of tolerance to the excitatory effect of morphine and cross-tolerance to the inhibitory action of β-endorphin in the isolated rat vas deferens

In the isolated rat vas deferens, morphine caused an increase in the neuromuscular twitch evoked by electrical stimulation. In rats chronically treated with morphine, the concentration of the opiate required to cause a 50% increase in the twitch was about 3 times larger than needed to elicit the same response in vasa from rats treated with a placebo. The simultaneous administration of naloxone plus morphine partially antagonized tolerance development by about 22%. Morphine tolerance was extended to other opiate- like alkaloids such as etonitazene and a derivative of azidomorphine (CAM). In contrast to the effects of morphine, β-endorphin inhibited neuromuscular transmission. Vasa from rats chronically treated with morphine were about 10 times less sensitive to the inhibitory effect of β-endorphin as compared to paired placebo treated controls. Chronic naloxone treatment in conjuction with morphine significantly reduced the cross-opiate tolerance by 66%. Present results suggest that morphine may interact at two different sites in the nerve terminals of the rat vas deferens.     

两种吗啡依赖大鼠模型脑内单胺神经递质水平的比较

目的通过对吗啡诱导的躯体依赖与精神依赖两种大鼠模型脑内单胺类递质水平的比较,探讨其在吗啡依赖形成中的作用。方法采用剂量递增法复制吗啡依赖大鼠模型,然后用纳洛酮催促,引起躯体戒断症状。连续给予吗啡（5mg／kg,ip）6d,引起大鼠产生显著的条件性位置偏爱效应。脑组织去甲肾上腺素（NE）、5-羟色胺（5-HT）和多巴胺（DA）含量采用荧光分光光度法测定。结果吗啡依赖大鼠催促戒断后脑内NE和5-HT水平明显升高,DA水平下降。吗啡在引起大鼠明显位置偏爱的同时,使大鼠脑内DA和5-HT水平显著升高,NE无明显改变。结论吗啡依赖的形成和戒断与脑内单胺神经递质有密切关系,吗啡依赖的躯体戒断症状与NE升高有关,而吗啡诱导的精神依赖则与脑内DA水平升高有关。     

Involvement of 3',5'-cyclic adenosine monophosphate-dependent protein kinase in regulation of Fos expression and tyrosine hydroxylase levels during morphine withdrawal in the hypothalamic paraventricular nucleus and medulla oblongata catecholaminergic cell groups

Morphine withdrawal stimulates the hypothalamic-pituitary-adrenocortical axis activity by activation of nucleus tractus solitarius (NTS)/ventrolateral medulla (VLM) noradrenergic pathways innervating the hypothalamic paraventricular nucleus (PVN). We investigated whether cAMP-dependent protein kinase (PKA) plays a role in this process by estimating changes in PKA immunoreactivity and the influence of inhibition of PKA on Fos protein expression and tyrosine hydroxylase (TH) immunoreactivity levels in the PVN and NTS/VLM during morphine withdrawal. Dependence on morphine was induced by a 7-day s.c. implantation of morphine pellets. Morphine withdrawal was precipitated on day 8 by an injection of naloxone (5 mg/kg s.c.). When opioid withdrawal was precipitated, an increase in PKA immunoreactivity levels was observed 90 min after naloxone administration in the PVN and NTS/VLM areas. Morphine withdrawal induced expression of Fos in the PVN and NTS/VLM, indicating an activation of neurones in those nuclei. TH immunoreactivity in NTS/VLM was increased 90 min after induction of morphine withdrawal, whereas there was a decrease in TH levels in the PVN at the same time point. When the selective PKA inhibitor HA-1004 was infused it greatly diminished the Fos expression observed in morphine-withdrawn rats. Furthermore, the changes in TH immunoreactivity were significantly modified by infusion of HA-1004. The present findings suggest that an up-regulated PKA-dependent transduction pathway might contribute to the activation of the hypothalamic-pituitary-adrenocortical axis in response to morphine withdrawal.     

吗啡耐受增加福尔马林致痛大鼠脊髓Fos和NADPH-d阳性神经元的表达

运用Ｆｏｓ免疫组织化学、ＮＡＤＰＨ－ｄ组织化学及Ｆｏｓ／ＮＡＤＰＨ－ｄ双标技术,研究了吗啡耐受对福尔马林致痛大鼠脊髓Ｆｏｓ、ＮＡＤＰＨ－ｄ阳性及Ｆｏｓ／ＮＡＤＰＨ－ｄ双标神经元表达的影响。结果观察到：在非吗啡耐受大鼠,福尔马林诱发的Ｆｏｓ－ｌｉｋｅ ｉｍｍｕｎｏｒｅａｃｔｉｖｉｔｙ（Ｆｏｓ－ＬＩ）主要分布在同侧脊髓背角浅层和颈部,急性静注吗啡可减少Ｆｏｓ－ＬＩ表达;长时间应用吗啡导致福尔马林诱发的     

The effect of intracerebroventricular 5,7-dihydroxytryptamine on morphine analgesia is time-dependent

The analgesic effect of morphine in the tail immersion test was studied in rats three and ten days after intracerebroventricular 5,7-dihydroxytryptamine (5,7-DHT) given to selectively destroy serotonergic neurons. Morphine analgesia was reduced three but not ten days after the neurotoxin. Ten days after 5,7-DHT, the inhibiting effect of metergoline, a serotonin antagonist, on morphine analgesia was still present, suggesting that functional recovery of the serotonergic system may partly explain the different results.     

Role of PKC-alpha,gamma isoforms in regulation of c-Fos and TH expression after naloxone-induced morphine withdrawal in the hypothalamic PVN and medulla oblongata catecholaminergic cell groups

We previously demonstrated that morphine withdrawal induced hyperactivity of the hypothalamus-pituitary-adrenocortical axis by activation of noradrenergic pathways innervating the hypothalamic paraventricular nucleus (PVN), as evaluated by Fos expression and corticosterone release. The present study was designed to investigate the role of protein kinase C (PKC) in this process by estimating changes in PKCalpha and PKCgamma immunoreactivity, and whether pharmacological inhibition of PKC would attenuate morphine withdrawal-induced c-Fos expression and changes in tyrosine hydroxylase (TH) immunoreactivity levels in the PVN and nucleus tractus solitarius/ ventrolateral medulla (NTS/VLM). Dependence on morphine was induced in rats by 7 day s.c. implantation of morphine pellets. Morphine withdrawal was induced on day 8 by an injection of naloxone. The protein levels of PKCalpha and gamma were significantly down-regulated in the PVN and NTS/VLM from the morphine-withdrawn rats. Morphine withdrawal induced c-Fos expression in the PVN and NTS/VLM, indicating an activation of neurons in those nuclei. TH immunoreactivity was increased in the NTS/VLM after induction of morphine withdrawal, whereas there was a decrease in TH levels in the PVN. Infusion of calphostin C, a selective protein kinase C inhibitor, produced a reduction in the morphine withdrawal-induced c-Fos expression. Additionally, the changes in TH levels in the PVN and NTS/VLM were significantly modified by calphostin C. The present results suggest that activated PKC in the PVN and catecholaminergic brainstem cell groups may be critical for the activation of the hypothalamic-pituitary adrenocortical axis in response to morphine withdrawal.     

Effect of morphine on polyphosphoinositides of erythrocytes of spontaneously hypertensive rats

Morphine (1 X 10(-5) mol/l) did not affect the incorporation of 32P into the phosphoinositides of erythrocytes from spontaneously hypertensive and normotensive Wistar Kyoto rats, whereas the content of triphosphoinositides was decreased. In spontaneously hypertensive rats the content of total phospholipids was decreased in the same ratio. Thus, the effect of morphine (at this concentration) on the membrane phospholipids of spontaneously hypertensive rats seems to be unspecific.     

The effects of morphine and various narcotic antagonist type analgesics on body temperature in rats

ED50s were determined for morphine, nalorphine, butorphanol and pentazocine induced hyperthermia in rats. Morphine produced a significant hyperthermia with the doses of 5–160 mg.kg in rats. The peak hyperthermic effect was found 1 hr after 5–20 mg/kg doses of morphine. Nalorphine, butorphanol and pentazocine produced biphasic effects on rectal temperature. Initially they produced a dose-dependent hyperthermia and later hypothermia. In a comparison of the hyperthermic ED50's of morphine, nalorphine, butorphanol and pentazocine it was found that butorphanol is more active than the others (ED50s were 4.7, 4.3, 0.54 and 11.5 mg/kg respectively). The narcotic antagonist naloxone significantly inhibited both morphine and antagonist type analgesic induced hyperthermia. These results suggests that a different mechanism(s) is involved in the hyperthermic actions of antagonist type analgesics and agonist drugs.     

Endothelin receptor antagonists restore morphine analgesia in morphine tolerant rats

Several neurotransmitter mechanisms have been proposed to play a role in the development of morphine tolerance. The present study provides evidence for the first time that endothelin (ET) antagonists can restore morphine analgesia in morphine tolerant rats. Tolerance to morphine was induced by subcutaneous implantation of six morphine pellets during a 7-day period. The degree of tolerance to morphine was measured by determining analgesic response (tail-flick latency) and hyperthermic response to morphine sulfate (8 mg/kg, subcutaneously (s.c.)) in placebo and morphine pellet implanted rats. The maximal tail-flick latency in morphine pellet-vehicle treated rats (7.54 s) was significantly lower (P<0.05) when compared to placebo pellet-vehicle treated rats (10s), indicating that tolerance developed to the analgesic effect of morphine. In separate sets of experiments, ET antagonists, BQ123 (10 microg, intracerebroventricularly (i.c.v.)) and BMS182874 (50 microg, i.c.v.) were administered in placebo and morphine tolerant rats. BQ123 was injected twice daily for 7 days and once on day 8. BMS182874 was administered only on day 8. Morphine (8 mg/kg, s.c.) was administered 30min after BQ123 or BMS182874 administration. It was found that both BQ123 and BMS182874 potentiated morphine analgesia in placebo and morphine tolerant rats. BQ123 potentiated tail-flick latency by 30.0% in placebo tolerant rats and 94.5% in morphine tolerant rats compared to respective controls. BMS182874 potentiated tail-flick latency by 30.2% in placebo tolerant rats and 66.7% in morphine tolerant rats. Morphine-induced hyperthermic effect was also potentiated by BQ123 and BMS182874. The duration of analgesic action was also prolonged by BQ123 and BMS182874. The effect of BMS182874 was less as compared to BQ123. BQ123 and BMS182874 are selective ET(A) receptor antagonists. Therefore, it is concluded that ET(A) receptor antagonists restore morphine analgesia in morphine tolerant rats.     

Effects of acute and chronic morphine on regional rat brain acetylcholine turnover rate

A simplified method to study the acetylcholine (ACh) turnover rate (TR_ACh) in brain parts of drug treated rats has been presented. In striatum and occipital cortex of rats receiving a large dose of morphine (140 μ moles/kg i.p.) or implanted chronically with morphine pellets, the TR_ACh is influenced in a different manner. The single injection of morphine reduced the synthesis of ACh in cortex but not in striatum. Morphine pellets decreased striatal TR_ACh but failed to alter the TR_ACh in occipital cortex. Naloxone reversed both changes of TR_ACh elicited by morphine although it was devoid of any effect of the synthesis of ACh in rat brain parts. We suggest that morphine may prevent the ACh release from neurons as proposed by others, however, this effect in striatum of rats receiving a single dose of morphine is masked by the simultaneous action of morphine on the dopaminergic nigrostriatal pathway which regulates the turnover rate of striatal ACh.     

Morphine diminishes the constancy of spontaneous uterine contractions, antagonizes the positive inotropic effects of prostaglandin E2, but not of prostaglandin F2 alpha and inhibits prostaglandin E and F outputs from the uterus of ovariectomized rats

The effects of morphine on the constancy of spontaneous contractions (isometric developed tension = IDT and contractile frequency = CF), in uterine strips isolated from ovariectomized rats and the influence of naloxone, were explored. The inotropic responses to added prostaglandins (PGs) E2 and F2 alpha and the influences of morphine and of morphine in the presence of naloxone on PG actions, were also determined. Moreover, the synthesis and outputs of PGs E and F from uteri and the effects of morphine alone and of morphine plus naloxone, were studied. Morphine (10(-6) M) significantly depressed uterine constancy of IDT during the first hours following delivery, but its action on CF did not differ from controls. Naloxone, neither at 10(-8) M nor at 10(-6) M, altered the negative inotropic influence of morphine on IDT. Exogenous PGs E2 and F2 alpha, stimulated uterine inotropism in a concentration-dependent fashion. Morphine altered dose-response curves for exogenous PGE2, evoking a parallel surmountable shift to the right, but did not affect the inotropic action of added PGF2 alpha. This antagonistic effect of the opioid was not altered by preincubation with naloxone. Basal synthesis and outputs of PGs E and F in uteri from ovariectomized rats were significantly depressed by morphine (10(-6) M) but not altered by incubating tissues with morphine in presence of naloxone. Results are discussed in terms of a presumptive dual action of morphine on uterine motility, i.e., antagonizing PGE2 receptors and inhibiting the synthesis of some PGs by the uterus. These influences of morphine do not appear to be subserved by the activation of mu opioid receptors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Morphine can stimulate prolactin release independent of a dopaminergic mechanism

Prolactin release is controlled by prolactin-release inhibiting factor (PIF), possibly dopamine, and an unidentified putative hypothalamic prolactin-releasing factor (PRF). Morphine and related opioids may indirectly stimulate prolactin release by inhibiting PIF release and (or) by stimulating putative PRF release. In the present study, we have completely blocked the dopaminergic receptors in normal male rats by pretreatment with a large dose of pimozide (3 mg/kg) to demonstrate if putative PRF has a role in morphine-induced prolactin release. Morphine sulfate (10 mg/kg) was still able to stimulate prolactin release in the rat without any functional dopaminergic PIF receptors. When naloxone (3 mg/kg) was injected 20 min before the morphine in the pimozide-treated rat, plasma prolactin concentration was not affected by morphine indicating that the stimulatory effect of this opioid on prolactin release in the pimozide-pretreated rat was mediated by mu-receptors. We can conclude that morphine can stimulate prolactin release through a mechanism apparently independent of dopaminergic receptors, one possible route being through a putative PRF.     

Effects of morphine on the 6-hydroxydopamine induced changes of the postnatal development of central noradrenaline neurons

Neonatal treatment with the catecholamine neurotoxin 6-hydroxydopamine (6-OH-DA) leads to permanent noradrenaline (NA) denervations of distant projections (e.g. in the neocortex) with a concomitant NA hyperinnervation in regions close to the perikarya (e.g. in the cerebellum) a "pruning effect' mainly affecting the locus coeruleus NA neuron system. Morphine administration after 6-OH-DA produced a significant potentiation of the 6-OH-DA-induced NA depletion in the olfactory bulb, spinal cord, frontal and occipital cortex, with a tendency for NA to increase in the mesencephalon, pons-medulla and cerebellum, when analysed in the adult stage. Morphine treatment alone had no effects on the NA levels in any region studied. Morphine was found to counteract the NA depletion induced by tyrosine hydroxylase inhibition in neonate rats, indicating that morphine reduces NA turnover. The present results are compatible with the view that morphine potentiates the 6-OH-DA-induced degeneration of NA nerve terminals, possibly related to the inhibitory action on NA neurons.     

Differential tolerance to the effects of morphine on evoked activity in the hippocampal slice

Morphine has been shown to have an excitatory effect on monosynaptically-evoked CA1 field potentials of the hippocampal slice manifest as an increase in amplitude of the primary population spike near threshold, and by the appearance of secondary and sometimes additional population spikes in response to a single stimulation. The effect of 3 concentrations of morphine on this response was studied in hippocampal slices taken from rats chronically treated with morphine or sham pellets. Slices from half of the rats in each treatment group were received in normal medium, the other half in medium containing 0.2 μM morphine. There was a significant indication of tolerance in the morphine-treated rats to the secondary spike effect but not to that of the primary spike. There were no significant differences due to the nature of the receiving medium.     

Effects of morphine on electrical activity of the emotion-producing zones in the hypothalamus of adult and aged rats

In the experiments performed on adult and aged rats, the effect of morphine on the electrical activity, recorded from the emotion-producing zones of the hypothalamus, the ventromedial nucleus (VMN), and the lateral hypothalamic area (LHA), was studied. In thein vitro experiments, an age-dependent reduction of background impulse activity (BIA) was found in the VMN single neurons, but not in the LHA neurons. Morphine reduced BIA in most of the VMN neurons, but enhanced it in the LHA neurons of adult rats, and enhanced BIA in the neurons of both structures of the aged rats. The inhibitory effect of morphine on the VMN and LHA neurons and its excitatory effect on the LHA neurons decreased with age. In thein vivo experiments, an age-dependent reduction of the background field electrical activity (background electrogram, BEG) was found in the neurons of both emotion-producing zones. Morphine reduced the BEG magnitude in the VMN and LHA more effectively in the aged rats than in the adult rats. The results allow us to suggest that both the opiate regulation of hypothalamic functions and formation of an opiate dependence in the adult rats essentially differ from those in the aged rats.Neirofiziologiya/Neurophysiology, Vol. 27, No. 2, pp. 126–133, March–April, 1995.