Effects of Cannabidiol on Morphine Conditioned Place Preference in Mice.

This study sought to determine whether the cannabis constituent cannabidiol attenuates the development of morphine reward in the conditioned place preference paradigm. Separate groups of mice received either saline or morphine in combination with one of four doses of cannabidiol using three sets of drug/no-drug conditioning trials. After drug-place conditioning, morphine mice displayed robust place preference that was attenuated by 10 mg/kg cannabidiol. Further, when administered alone, this dose of cannabidiol was void of rewarding and aversive properties. The finding that cannabidiol blocks opioid reward suggests that this compound may be useful in addiction treatment settings.

Specific behavioral and cellular adaptations induced by chronic morphine are reduced by dietary omega-3 polyunsaturated fatty acids.

Opiates, one of the oldest known drugs, are the benchmark for treating pain. Regular opioid exposure also induces euphoria making these compounds addictive and often misused, as shown by the current epidemic of opioid abuse and overdose mortalities. In addition to the effect of opioids on their cognate receptors and signaling cascades, these compounds also induce multiple adaptations at cellular and behavioral levels. As omega-3 polyunsaturated fatty acids (n-3 PUFAs) play a ubiquitous role in behavioral and cellular processes, we proposed that supplemental n-3 PUFAs, enriched in docosahexanoic acid (DHA), could offset these adaptations following chronic opioid exposure. We used an 8 week regimen of n-3 PUFA supplementation followed by 8 days of morphine in the presence of this diet. We first assessed the effect of morphine in different behavioral measures and found that morphine increased anxiety and reduced wheel-running behavior. These effects were reduced by dietary n-3 PUFAs without affecting morphine-induced analgesia or hyperlocomotion, known effects of this opiate acting at mu opioid receptors. At the cellular level we found that morphine reduced striatal DHA content and that this was reversed by supplemental n-3 PUFAs. Chronic morphine also increased glutamatergic plasticity and the proportion of Grin2B-NMDARs in striatal projection neurons. This effect was similarly reversed by supplemental n-3 PUFAs. Gene analysis showed that supplemental PUFAs offset the effect of morphine on genes found in neurons of the dopamine receptor 2 (D2)-enriched indirect pathway but not of genes found in dopamine receptor 1(D1)-enriched direct-pathway neurons. Analysis of the D2 striatal connectome by a retrogradely transported pseudorabies virus showed that n-3 PUFA supplementation reversed the effect of chronic morphine on the innervation of D2 neurons by the dorsomedial prefontal and piriform cortices. Together these changes outline specific behavioral and cellular effects of morphine that can be reduced or reversed by dietary n-3 PUFAs.

[Inhibition of morphine intake by antibodies to serotonin-modulating anticonsolidation protein in model of self-administration in rats].

The article concerns study of effects of polyclonal antibodies to serotonin-modulating anticonsolidation protein (SMAP) being in direct dependence on serotonin level and providing intracellular transduction of serotonergic signal, on positive reinforcement effect of morphine in rats. The task was formed in Wistar male rats in the model of morphine self-administration as a result of pressing of one of two levers attached to the wall, joined to the pump delivering each time 100 µg of morphine directly into the vena jugularis. In the 1st series of studies brain cingulate cortex and hypothalamus were taken from the rats achieved stable level of morphine intake and SMAP level was measured with indirect immune-enzyme assay. It was shown that in the morphine-self-injected rats SMAP level in the cingulate cortex is significantly upregulated (p = 0.01), while in the hypothalamus it was left unchanged. In the 2nd series of studies the rats with stable level of morphine intake were administered intraperitoneally with anti-SMAP rabbit polyclonal antibodies (experimental group) or non-immune γ-globulins (control group). Soon after antibodies administration the animals of the experimental group demonstrated manifold decrease of morphine intake lasted for 8 days (p < 0.008), whereas it did not change in the controls. SMAP upregulation in the brain cingulate cortex in the rats with stable morphine intake, obviously, indicates to its engagement in positive reinforcement effect of morphine. Blockade of SMAP activity with anti-SMAP antibodies in the nerve cells induced sharp decrease of morphine intake due to disturbances of transduction through intracellular serotonin's signal channels.

Naloxone blocks the beneficial effects of aqueous extract of Murraya koenigii (L.) Spreng leaves in models of pain.

AIM: This study investigated the antinociceptive effects of aqueous extract of Murraya koenigii (AEMK) leaves (200, 400 and 800 mg/kg, orally) on animal models of acute and persistent pain and its modulation by naloxone. MATERIALS AND METHODS: Antinociceptive effects were assessed using tail-flick, hot plate and formalin tests in mice. To differentiate between central and peripheral antinociceptive effect of AEMK, naloxone (2 mg/kg) was administered along with the 800 mg/kg dose of extract. Morphine was used as a standard drug. RESULTS: AEMK and morphine significantly increased the tail-flick latency (tfl) and paw licking/jumping latency in tail-flick and hot plate tests, respectively, in comparison to control. Also, in both the tests AEMK and morphine significantly increased the AUC0-120 min. In formalin test, AEMK (400 mg/kg and 800 mg/kg) and morphine significantly reduced licking time in both early and late phases in comparison to control. CONCLUSIONS: Thus, in all three pain models AEMK showed antinociceptive effect, which was blocked by naloxone suggesting the involvement of opioidergic central mechanism.

[Study on acting mechanism of anti-morphine conditioned place preference between aqueous extract of Corydalis yanhusuo and L-THP and comparison of their effects].

OBJECTIVE: To study the acting mechanism of anti-morphine conditioned place preference (CPP) between aqueous extract of Corydalis yanhusuo and L-THP and compare their effects. METHOD: The CPP model was established by injecting morphine in rats with a increasing dose for 10 days, with the initial dose of 10 g x kg(-1) and the final dose of 100 g x kg(-1), 10 mg x kg(-1) was increased each day, thus 100 mg x kg(-1) was injected by d 10. Having been treated with differential doses (2, 1 and 0.5 g x kg(-1)) of C. yanhusuo (containing L-THP: 0.153, 0.077 and 0.038 mg x kg(-1) respectively) and L-THP (3.76, 1.88 and 0.94 mg x kg(-1)) for six days, the CPP effect in rats was detected. Both colorimetry and immunohistochemistry methods were adopted to detect the content of glutamate neurotransmitter in each brain region and the expression of NR2B in VTA-NAc-PFC neuroanatomical circuit. RESULT: Compared with the physiological saline treatment group, C. yanhusuo (2, 1 g x kg(-1)) and L-THP (3.76 and 1.88 mg x kg(-1)) groups showed a notably shorter retention period of rats in white boxes (morphine-accompanied boxes) (P < 0.05 or P < 0.01) and remarkably lower glutamic acid content in VTA, NAc and PFC and NR2B expression. CONCLUSION: Both C. yanhusuo and L-THP can substantially inhibit the effect of morphine CPP, reduce the increasing glutamic acid content in VTA-NAc-PFC neuroanatomical circuit and down-regulated NR2B expression, which may be one of mechanisms on reducing the effect of morphine CPP. C. yanhusuo preparations containing L-THP (1 x ) showed 24-fold effect of L-THP monomer of single application in terms of the behaviouristics of inhibitory effect on CPP as well as the similarity in terms of transmitter glutamic acid of in VTA-NAc-PFC neuroanatomical circuit and pharmacological mechanism of NR2B.

Saffron (Crocus sativus) ethanolic extract and its constituent, safranal, inhibits morphine-induced place preference in mice.

The effects of saffron ethanolic extract and its constituent, safranal, on the acquisition and expression of morphine-induced place preference (CPP) in male Swiss Webster mice (20-25 g) were investigated in the present study. An unbiased place conditioning method was applied for assessment of morphine reward properties. The saffron extract and safranal were administered intraperitoneally (i.p.) during (acquisition) or after induction (expression) of morphine CPP. In a pilot study, the extract and safranal were alone administered to the animals to assess if they have any reward properties. Subcutaneous (s.c.) of morphine (4 and 8 mg kg(-1)) and extract (50 mg kg(-1); i.p.) induced CPP. Extract (10, 50 and 100 mg kg(-1); i.p.) reduced the acquisition and expression of morphine CPP. The same results were obtained when safranal (1, 5 and 10 mg kg(-1), i.p.) was used. It may be concluded that both ethanolic saffron extract and safranal can inhibit the acquisition and expression of morphine-induced CPP in the mice.

Ginsenoside Rg1 restores the impairment of learning induced by chronic morphine administration in rats.

Rg1, as a ginsenoside extracted from Panax ginseng, could ameliorate spatial learning impairment. Previous studies have demonstrated that Rg1 might be a useful agent for the prevention and treatment of the adverse effects of morphine. The aim of this study was to investigate the effect of Rg1 on learning impairment by chronic morphine administration and the mechanism responsible for this effect. Male rats were subcutaneously injected with morphine (10 mg/kg) twice a day at 12 hour intervals for 10 days, and Rg1 (30 mg/kg) was intraperitoneally injected 2 hours after the second injection of morphine once a day for 10 days. Spatial learning capacity was assessed in the Morris water maze. The results showed that rats treated with Morphine/Rg1 decreased escape latency and increased the time spent in platform quadrant and entering frequency. By implantation of electrodes and electrophysiological recording in vivo, the results showed that Rg1 restored the long-term potentiation (LTP) impaired by morphine in both freely moving and anaesthetised rats. The electrophysiological recording in vitro showed that Rg1 restored the LTP in slices from the rats treated with morphine, but not changed LTP in the slices from normal saline- or morphine/Rg1-treated rats; this restoration could be inhibited by N-methyl-D-aspartate (NMDA) receptor antagonist MK801. We conclude that Rg1 may significantly improve the spatial learning capacity impaired by chonic morphine administration and restore the morphine-inhibited LTP. This effect is NMDA receptor dependent.

Inhibitory effects of ginseng total saponin on up-regulation of cAMP pathway induced by repeated administration of morphine.

We have reported that ginseng total saponin (GTS) inhibited the development of physical and psychological dependence on morphine. However, the possible molecular mechanisms of GTS are unclear. Therefore, this study was undertaken to understand the possible molecular mechanism of GTS on the inhibitory effects of morphine-induced dependence. It has been reported that the up-regulated cAMP pathway in the LC of the mouse brain after repeated administration of morphine contributes to the feature of withdrawals. GTS inhibited up-regulation of cAMP pathway in the LC after repeated administration of morphine in this experiment. GTS inhibited cAMP levels and protein expression of protein kinase A (PKA). In addition, GTS inhibited the increase of cAMP response element binding protein (CREB) phosphorylation. Therefore, we conclude that the inhibitory effects of GTS on morphine-induced dependence might be mediated by the inhibition of cAMP pathway.

Inhibitory effects of berberine against morphine-induced locomotor sensitization and analgesic tolerance in mice.

We previously reported that a methanolic extract of Coptis japonica, which is a well-known traditional oriental medicine, inhibits morphine-induced conditioned place preference (CPP) in mice. Berberine is a major component of Coptis japonica extract, and it has been established that the adverse effects of morphine on the brain involve dopamine (DA) receptors. However, to our knowledge, no study has investigated the inhibitory effects of berberine on morphine-induced locomotor sensitization and analgesic tolerance in mice. Here, we investigated the effects of berberine on morphine-induced locomotor sensitization and on the development of analgesic tolerance. Furthermore, we examined the effects of berberine treatment on N-methyl-D-aspartate (NMDA) receptor channel activity expressed in Xenopus laevis oocytes. Berberine was found to completely block both morphine-induced locomotor sensitization and analgesic tolerance, and reduce D(1) and NMDA receptor bindings in the cortex. Moreover, berberine markedly inhibited NMDA current in Xenopus laevis oocytes expressing NMDA receptor subunits. Our results suggest that the inhibitory effects of berberine on morphine-induced locomotor sensitization and analgesic tolerance are closely related to the modulation of D1 and NMDA receptors, and that berberine should be viewed as a potential novel means of attenuating morphine-induced sensitization and analgesic tolerance.

Analysis of the mechanism of antinociceptive action of niga-ichigoside F1 obtained from Rubus imperialis (Rosaceae).

We have previously verified that niga-ichigoside F(1) (NI), a triterpene isolated from Rubus imperialis, exhibits significant and potent antinociceptive action when evaluated in some pharmacological models of pain in mice. This effect was confirmed in other experimental models and also the mechanism of action has been evaluated. The antinociception caused by NI (60 mg kg(-1)) in both phases of the formalin test was significantly attenuated by intraperitoneal injection of mice with haloperidol (a dopaminergic antagonist, 0.20 mg kg(-1)) and L-arginine (precursor of nitric oxide, 600 mg kg(-1)). Regarding the cholinergic system, atropine (a cholinergic antagonist 60 mg kg(-1)) reverted only the second phase. The effect of NI was not affected by treatment of mice with yohimbine (an alpha2-adrenoceptor antagonist, 0.15 mg kg(-1)). The same pharmacological profile was observed for the administration of naloxone (an opioid receptor antagonist, 1 mg kg(-1)). On the other hand, intraperitoneal injection caused dose-related and significant effects against glutamate- and capsaicin-induced pain, respectively. In conclusion, the marked antinociception of NI appears to be related to the dopaminergic, cholinergic, glutamatergic, tachykininergic and oxinitrergic systems, supporting the ethnomedical use of Rubus imperialis (Rosaceae).

Pharmacological action of Panax 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.

Antinociception, tolerance and withdrawal symptoms induced by 7-hydroxymitragynine, an alkaloid from the Thai medicinal herb Mitragyna speciosa.

7-Hydroxymitragynine is a potent opioid analgesic alkaloid isolated from the Thai medicinal herb Mitragyna speciosa. In the present study, we investigated the opioid receptor subtype responsible for the analgesic effect of this compound. In addition, we tested whether development of tolerance, cross-tolerance to morphine and naloxone-induced withdrawal signs were observed in chronically 7-hydroxymitragynine-treated mice. Subcutaneous (s.c.) administration of 7-hydroxymitragynine produced a potent antinociceptive effect mainly through activation of mu-opioid receptors. Tolerance to the antinociceptive effect of 7-hydroxymitragynine developed as occurs to morphine. Cross-tolerance to morphine was evident in mice rendered tolerant to 7-hydroxymitragynine and vice versa. Naloxone-induced withdrawal signs were elicited equally in mice chronically treated with 7-hydroxymitragynine or morphine. 7-Hydroxymitragynine exhibited a potent antinociceptive effect based on activation of mu-opioid receptors and its morphine-like pharmacological character, but 7-hydroxymitragynine is structurally different from morphine. These interesting characters of 7-hydroxymitragynine promote further investigation of it as a novel lead compound for opioid studies.

The N-Methyl-D-aspartate receptor antagonist dizocilpine inhibits associative antinociceptive tolerance to morphine in mice: relation with memory.

I and coauthor previously reported the memory facilitation effect of morphine. The main purpose of this study was to evaluate the involvement of the N-methyl-D-aspartate (NMDA) receptor in associative tolerance to morphine by a contextual procedure. Antinociceptive response latency was measured by the tail-pinch method during repeated morphine (5 mg/kg, s.c.) injection for four consecutive days with pretreatment by dizocilpine (0.01, 0.05, 0.1 mg/kg, i.p.) at 30 min prior to morphine injection in the training phase and before and after morphine injection in the test phase. The nociceptive response latency was shortened by the single administration of dizocilpine (0.05 to 0.25 mg/kg, i.p.). Pretreatment by dizocilpine at 0.05 or 0.1 mg/kg weakened the antinociception to morphine on Day 1, but decreased the tolerance throughout the training phase. In the test phase, the animals were allocated into the same and different contexts. In the test phase, hyperalgesia before morphine injection in the same context and antinociception after morphine injection in the different context were evident in the saline-pretreated group in the training phase, but they were not observed in those contexts in the dizocilpine-pretreated groups. These results suggest that memory dysfunction with dizocilpine inhibits the recovery of associative tolerance to morphine by contextual change.

4-Caffeoyl-1,5-quinide in roasted coffee inhibits [3H]naloxone binding and reverses anti-nociceptive effects of morphine in mice.

RATIONALE: Cinnamoylquinides are formed from the corresponding chlorogenic acids during coffee roasting. Instant coffee has been shown to displace binding of the mu opioid receptor antagonist, [3H]naloxone, but the putative active agent, feruloylquinide, has not been characterized. OBJECTIVES: The goal was to identify the active agent(s) in coffee by measuring the binding affinity of individual cinnamoyl-1,5-quinides to the human mu opioid receptor, and determine the effects of these compounds on morphine-induced anti-nociceptive behavior in mice. METHODS: Cinnamoyl-1,5-quinides in extracts of decaffeinated instant coffee were quantified by reverse-phase HPLC comparisons with synthetic samples of 3-coumaroyl-1,5-quinide and 4-coumaroyl-1,5-quinide, 3-caffeoyl-1,5-quinide and 4-caffeoyl-1,5-quinide (4-CQL) 3-feruloyl-1,5-quinide and 4-feruloyl-1,5-quinides and 3,4-dicaffeoyl-1,5-quinide (DICAQ). Affinities of the cinnamoyl-1,5-quinides and decaffeinated instant coffee extract were determined by displacement of [3H]naloxone binding in cultured HEK-MOR cells. Inhibition of the anti-nociceptive activity of morphine (1 mg/kg IP) was determined in C57BL/6J mice using the hot plate test at 52 degrees C. RESULTS: Extract of decaffeinated instant coffee produced a displacement K(i) of 42+/-16 mg/l, while the K(i) of a synthetic sample of 4-CQL was 4.4+/-0.4 microM. Compounds with a cinnamoyl substituent in the 4-position of the quinide, i.e. 4-CQL, DICAQ, 3,4-diferuloyl-1,5-quinide, and 3,4-dicoumaroyl-1,5-quinide, had affinities for the mu opioid receptor in the low micromolar range. In the hot plate test, coffee extract, containing 0.78% of 4-CQL, reversed the anti-nociceptive effect of morphine at 10 mg/kg IP. Two cinnamoyl-1,5-quinides found in roasted coffee, DICAQ, and 4-CQL, were active at 1 and 0.1 mg/kg IP, respectively. CONCLUSIONS: These results suggest that the previously reported anti-opioid activity of instant coffee is caused primarily by the presence of 4-CQL, and to lesser extent by other cinnamoyl-1,5-quinides.

[Effects of ginsenosides on the actions of morphine].

The effects of ginsenosides on the actions of morphine are summarized. It mainly focuses on the antagonistic effects of ginsenosides on morphine-induced changes of animal behaviors, neural system functions and cell signaling transduction.

Potentiated antibodies against morphine: effects on biogenic amines and lipid peroxidation in chronically morphinized rats.

The efficiency of potentiated antibodies against morphine was studied on the model of chronic morphine intoxication. Test antibodies stimulated catecholamine metabolism in the hypothalamus (i.e., prevented initiation of catecholamine- and histaminergic peripheral reactions) and normalized lipid peroxidation.

Effects of Coptis japonica on morphine-induced conditioned place preference in mice.

Morphine, an analgesic with significant abuse potential, is considered addictive because of drug craving and psychological dependence. It is reported that repeated treatment of morphine can produce conditioned place preference (CPP) showing a reinforcing effect in mice. CPP is a useful method for the screening of morphine-induced psychological dependence. In the present study, we investigated the effect of the methanolic extract of Coptis japonica (MCJ) on morphine-induced CPP in mice. Furthermore, we examined c-fos expression in the parietal cortex, piriform cortex, striatum, nucleus accumbens, and hippocampus of the morphine-induced CPP mouse brain. Treatment of MCJ 100 mg/kg inhibited morphine-induced CPP. Expression of c-fos was increased in the cortex, striatum, nucleus accumbens, and hippocampus of the morphine-induced CPP mouse brain. These increases of expression were inhibited by treatment with MCJ 100 mg/kg, compared to the morphine control group. Taken together, these results suggest that MCJ inhibits morphine-induced CPP through the regulation of c-fos expression in the mouse brain.

Central antinociceptive effect of a hydroalcoholic extract of Dioclea grandiflora seeds in rodents.

The acute treatment of rats and mice with a hydroalcoholic extract from the seeds of Dioclea grandiflora (EHDg) at doses of 250 and 500 mg/kg, by intraperitoneal or oral administration, produced a significant antinociceptive effect in the tail flick and hot plate tests, an effect which was inhibited by naloxone. EHDg given to mice daily for 30 days at a dose of 500 mg/kg, did not cause any observable toxic effect nor any alteration in the pattern of antinociceptive response by the tail immersion test during the course of this treatment. These results suggest that EHDg has a central antinociceptive action devoid of tolerance effect typical of opioid drugs.

Non-peptidergic OP4 receptor agonist inhibits morphine antinociception but does not influence morphine dependence.

The non-peptidergic opioid receptor-like 1 (ORL1, OP4) receptor ligand, Ro 64-6198 [(1S,3aS)-8-(2,3,3a,4,5,6-hexahydro-1H-phenalen-1-yl)-1-phenyl-1,3,8-triaza-spiro[4,5]decan-4-one], is a full agonist of the OP4 receptor. The aim of this study was to evaluate whether this compound influences morphine antinociception and dependence in mice. Ro 64-6198 inhibits the acute analgesic effect of morphine in the tail-immersion test, however, when given chronically during the acquisition of morphine dependence, development of this dependence is not prevented. The acute injection of Ro 64-6198 suppresses withdrawal escape jumps in morphine dependent mice, though this effect may be a result of the loss of locomotor activity induced by this compound and/or its myorelaxant action. The study provides evidence that stimulation of the OP4 receptor suppresses acute morphine antinociception, but is not sufficient to inhibit the development of morphine dependence in mice.

Effect of precipitated morphine withdrawal on post-translational processing of prothyrotropin releasing hormone (proTRH) in the ventrolateral column of the midbrain periaqueductal gray.

We have demonstrated that during opiate withdrawal, preprothyrotropin releasing hormone (preproTRH) mRNA is increased in neurons of the midbrain periaqueductal gray matter (PAG) while the concentration of TRH remained unaltered, suggesting that the processing of proTRH may be different in this region of the brain. The aim of the present study was to determine which of the proTRH-derived peptides are affected by opiate withdrawal in the PAG. These changes were compared to other TRH-containing areas such as the hypothalamic paraventricular nucleus (PVN), median eminence (ME) and the lateral hypothalamus (LH). Control and morphine-treated rats 24 h following naltrexone-precipitated withdrawal were decapitated and the brain microdissected. Pooled samples from each animal group were acid extracted, and peptides were electrophoretically separated then analyzed by specific radioimmunoassay. Opiate withdrawal caused a significant change in the level of some post-translational processing products derived from the TRH precursor. In the PAG, opiate withdrawal resulted in an accumulation of the intervening preproTRH(83-106) peptide from the N-terminal side of the prohormone, while the levels of the C-terminal preproTRH(208-285) peptide were reduced, with no change in preproTRH(25-50) or TRH, itself, as compared to control animals. Immunohistochemical analysis also showed significant increases in cellular preproTRH(83-106) peptide immunolabeling in the PAG. Opiate withdrawal in the lateral hypothalamus, unlike from the PAG, was accompanied by an increase in the concentration of TRH. In addition, western blot analysis showed that during opiate withdrawal, the mature form of the prohormone convertase 2 (PC2) increased only in PAG as compared with their respective controls. Thus, these results demonstrate a region-specific regulation of TRH prohormone processing in the brain, which may engage PC2, further suggesting a role for specific proTRH-derived peptides in the manifestations of opiate withdrawal.