Cholecystokinin receptor-1 mediates the inhibitory effects of exogenous cholecystokinin octapeptide on cellular morphine dependence
© Wen et al.; licensee BioMed Central Ltd. 2012
Received: 15 November 2011
Accepted: 8 June 2012
Published: 8 June 2012
Cholecystokinin octapeptide (CCK-8), the most potent endogenous anti-opioid peptide, has been shown to regulate the processes of morphine dependence. In our previous study, we found that exogenous CCK-8 attenuated naloxone induced withdrawal symptoms. To investigate the precise effect of exogenous CCK-8 and the role of cholecystokinin (CCK) 1 and/or 2 receptors in morphine dependence, a SH-SY5Y cell model was employed, in which the μ-opioid receptor, CCK1/2 receptors, and endogenous CCK are co-expressed.
Forty-eight hours after treating SH-SY5Y cells with morphine (10 μM), naloxone (10 μM) induced a cAMP overshoot, indicating that cellular morphine dependence had been induced. The CCK receptor and endogenous CCK were up-regulated after chronic morphine exposure. The CCK2 receptor antagonist (LY-288,513) at 1–10 μM inhibited the naloxone-precipitated cAMP overshoot, but the CCK1 receptor antagonist (L-364,718) did not. Interestingly, CCK-8 (0.1-1 μM), a strong CCK receptor agonist, dose-dependently inhibited the naloxone-precipitated cAMP overshoot in SH-SY5Y cells when co-pretreated with morphine. The L-364,718 significantly blocked the inhibitory effect of exogenous CCK-8 on the cAMP overshoot at 1–10 μM, while the LY-288,513 did not. Therefore, the CCK2 receptor appears to be necessary for low concentrations of endogenous CCK to potentiate morphine dependence in SH-SY5Y cells. An additional inhibitory effect of CCK-8 at higher concentrations appears to involve the CCK1 receptor.
This study reveals the difference between exogenous CCK-8 and endogenous CCK effects on the development of morphine dependence, and provides the first evidence for the participation of the CCK1 receptor in the inhibitory effects of exogenous CCK-8 on morphine dependence.
KeywordsCholecystokinin octapeptide CCK1 receptor CCK2 receptor Morphine Cellular dependence cAMP overshoot
Opioids are not only potent analgesics but are also drugs of abuse, which greatly limits their clinical use. Chronic use of opioids results in the development of tolerance and dependence. Recent studies suggest that non-opioid systems could be important targets for the treatment of opioid dependence [1, 2]. Antagonism of opioid effects by endogenous anti-opioid peptides is common . Cholecystokinin (CCK) was initially identified as a gastrointestinal hormone, and was subsequently found in the central and peripheral nervous systems. It occurs as various sized peptides, including 4, 8, 33, 39 and 58 amino acid forms . Cholecystokinin octapeptide (CCK-8) is the most potent endogenous anti-opioid peptide . For example, morphine treatments enhance the overflow of CCK, whereas CCK-8 and its analogues attenuate the analgesic effects of morphine [6–8]. Furthermore, studies have demonstrated that the CCK system modulates a variety of physiological processes, and that CCK-8 interacts with the GABAergic and dopaminergic systems. Thus, CCK-8 plays a significant role in a wide range of central actions including memory and drug reward [9–12]. Overlap in the distributions of CCK and opioid receptors may be observed in some anatomical regions that are involved in opioid antinociception and dependence . These findings indicate that the CCK system is related to the modulation of morphine tolerance and dependence.
The administration of CCK receptor antagonists can prevent or reverse tolerance to systemic exogenous opioids or electroacupuncture-induced analgesia, as well as suppress morphine withdrawal syndromes [14–16]. Interestingly, CCK receptor activation can reverse morphine tolerance . We previously found that chronic pretreatment with exogenous CCK-8 significantly inhibited naloxone-precipitated withdrawal symptoms, which is the same effect as CCK-receptor antagonists [18, 19]. These phenomena suggest that the effects of exogenous CCK-8 are distinct from the role of endogenous CCK. With regard to dosage, CCK-8 was able to prevent morphine dependence at high, but not low, concentrations . However, no studies have reported a dose–response curve of CCK-8 on morphine dependence. On the basis of the pharmacological properties and specificities for ligand binding, CCK receptors have been identified for the CCK1 and CCK2 receptor subtypes . The expression pattern of these CCK receptors in mammals appears to be tissue-specific . Several studies have revealed that two different CCK receptors (CCK1 and CCK2) have opposing influences on behavioural and hormonal actions [23, 24]. Thus, CCK receptor subtypes that mediate the inhibitory effects of exogenous CCK-8 on morphine dependence remain to be determined.
The biological basis of tolerance and dependence induced by chronic exposure to opioids is thought to be due to molecular, cellular, and neural network adaptations. On the cellular level, opioid dependence is characterised by a significant elevation of adenylyl cyclase (AC) activity after drug withdrawal, which is a regulatory phenomenon termed "AC supersensitivity" or "cAMP overshoot" [25–27]. A cAMP overshoot represents an opioid-dependent state in vitro and has been utilised in the study of the effects of morphine dependence . This present study evaluates the effects of CCK-8 on the AMP overshoot based on a cellular model and aims to clarify the exact effects of exogenous CCK-8. In addition, the subtypes of CCK receptor that mediate the function of CCK-8 on morphine dependence are also investigated.
In vitro model of morphine dependence
The effect of chronic morphine exposure on the endogenous CCK system
The effect of CCK receptor antagonists on naloxone-precipitated cAMP overshoot in SH-SY5Y cells after chronic morphine exposure
The effect of exogenous CCK-8 on naloxone-precipitated cAMP overshoot in SH-SY5Y cells after chronic morphine exposure
Blockade of the CCK1 receptor attenuates the effect of exogenous CCK-8 on naloxone-precipitated cAMP overshoot after chronic morphine exposure
In this present study, we describe a distinct effect of exogenous CCK-8 on the development of morphine dependence in vitro. Moreover, we provide the first piece of evidence that a CCK1 receptor antagonist can reverse the inhibitory effects of exogenous CCK-8 on morphine dependence. We also find that endogenous CCK exerts a potential facilitative effect via the CCK2 receptor. This suggests opposing roles of CCK1 and CCK2 receptors in the development of morphine dependence.
First, a suitable cell model was selected for this study. The SH-SY5Y cell line is derived from a human neuroblastoma cell line, SK-N-SH, by three rounds of subcloning. The SH-SY5Y cells are dopamine beta hydroxylase active, acetylcholinergic, glutamatergic and adenosinergic, and express abundant and functional μ- and δ-opioid receptors. SH-SY5Y cells have been extensively used for studies of opioid receptor regulation and intracellular signaling. Moreover, co-expression of the opioid and CCK systems in SH-SY5Y cells was confirmed, and CCK is endogenously expressed in SH-SY5Y cells. This system is useful for the study of the potential regulatory effects of exogenous CCK-8 on morphine dependence.
The interaction between CCK and opioids was first reported by Itoh et al. They showed that pre-treatment with CCK suppressed anti-nociception induced by β-endorphin . A subsequent in vivo microdialysis study found that the extracellular levels of CCK significantly increased after morphine administration, thus acting as a negative feedback modulator and a potent anti-opioid peptide [6, 7, 30]. Studies have confirmed that endogenous CCK potentiates, and the CCK antagonist attenuates the tolerance and dependence of opioids [31, 32]. The presence of opioid receptors in CCK-containing neurons suggest a potential direct influence of opioids on CCK release . However, earlier studies have failed to show an affinity of CCK for opioid receptors, indicating that CCK does not behave as a classical receptor antagonist via binding to opioid receptors . Han et al. found that the binding of CCK-8 to the CCK receptor reduces the binding affinity of μ-opioid receptor ligands, implying that receptor–receptor interaction between CCK and opioid systems may occur in an indirect manner . The molecular cloning of CCK receptor subtypes, one from the pancreas (type-1) and another from human brain (type-2), has confirmed the pharmacological classification of CCK receptors. The CCK2 receptor is predominantly localised in the CNS, and mainly mediates anxiety, panic attacks, pain and drug dependence [36–38]. The CCK1 receptor is present in discrete regions of the brain and has a low affinity for central CCK , and its function is poorly understood with only a few reports investigating the central role in food intake regulation . The use of highly selective receptor antagonists and antisense approaches has shown, at least in the rodent, that CCK2 receptors mediate the anti-opioid function of CCK [41–43]. The present study shows that co-pretreatment with LY-288,513 and morphine significantly inhibited the naloxone-precipitated cAMP overshoot in SH-SY5Y cells, but that co-pretreatment with L-364,718 displayed no effect. We verified that endogenous CCK played an anti-opioid role and potentiated the development of morphine dependence via the CCK2 receptor.
Together with our previous results, we found that exogenous CCK-8 pretreatment significantly inhibited morphine dependence in vitro and in vivo. These results show that the treatments of the CCK receptor agonist and antagonist demonstrated the same effect on morphine dependence. Moreover, CCK-8 treatment did not affect basal or forskolin-stimulated cAMP levels, suggesting that the effect of exogenous CCK-8 was not simply a direct action on cAMP. Several studies have reported that small doses of CCK inhibit the anti-nociceptive action of opioids, whereas large doses of CCK induce analgesia . We previously revealed that CCK-8 suppressed the binding affinity of the μ-opioid receptor in SH-SY5Y cells at concentrations of 1 nM, while it increased the expression of the endogenous opioid peptide from 0.1 to 1 μM . The dose–response curve of CCK-8 was inversely U-shaped, and CCK-8 displayed a dose-dependent, biphasic effect . We found that only high concentrations of CCK-8 were able to attenuate the cAMP overshoot in a dose-dependent manner. Thus, observations of exogenous CCK-8 may represent pharmacological effects, rather than physiological effects of endogenous CCK.
A previous study indicated that the CCK1 receptor was ineffective in the development of morphine dependence . Nevertheless, we found that a high dose of exogenous CCK-8 markedly attenuated the naloxone precipitated cAMP overshoot via the CCK1 receptor. We concluded that the CCK1 and CCK2 receptors play unique and distinct roles in physiology and pathophysiology. Moreover, data showing that CCK1 receptors mediate mnemonic effects, and that CCK2 receptors mediate amnestic effects, have been reported . Furthermore, CCK evokes [Ca2+i signaling by the influx of extracellular calcium, likely through L-type calcium channels, and an antagonist for the CCK1 receptor blocked [Ca2+i response to CCK-8 [49, 50]. CCK produces direct neuronal depolarisation via CCK1 receptors and inhibits GABAergic synaptic transmission , while CCK2 receptor activation augments long-term potentiation in hippocampal slices . CCK-8, the predominant central form of CCK, has a high affinity for the CCK2 receptor, but a low affinity for the CCK1 receptor. The CCK1 receptor is activated only in the presence of high CCK-8 levels, and exerts a different effect from the CCK2 receptor on morphine dependence. Due to the inhibitory function of LY-288,513 and CCK-8 on cAMP overshoot, the cumulative effect of LY-288,513 and exogenous CCK-8 on cAMP overshoot was not observed. The role of CCK2 receptor in the process of exogenous CCK-8 regulation on morphine dependence can not be ruled out.
In conclusion, we identified a difference between the role of the CCK1 and CCK2 receptor on the development of morphine dependence and an inhibitory effect of high-doses of exogenous CCK-8 on cellular morphine dependence. In addition, this study provides the first evidence for the participation of the CCK1 receptor in the mechanism by which exogenous CCK-8 inhibits morphine dependence.
Materials and methods
Morphine hydrochloride was purchased from Shenyang First Pharmaceutical Factory (Liaoning, China). CCK-8, IBMX, naloxone and forskolin were purchased from Sigma (Sigma, St. Louis, MO, USA). Retinoic acid (RA) was purchased from Alfa Aesar (Alfa Aesar, Heysham, UK). The CCK1 receptor antagonist, L-364,718, and CCK2 receptor antagonist, LY-288,513, were purchased from Tocris Bioscience (Tocris Cookson, Northpoint, UK). DMEM/F12 medium was purchased from Invitrogen Corporation (Gibco™, Grand Island, NY, USA). Fetal bovine serum was purchased from PAA Laboratories (PAA, Strasse, Pasching, Austria). LANCE™ cAMP kits were purchased from PerkinElmer (PerkinElmer, MA, USA). CCK-8 was suspended in vehicle consisting of 1% ammonia saline solution at 1 mg/ml, and the CCK receptor antagonists were suspended in DMSO at 1 mg/ml.
Human SH-SY5Y neuroblastoma cells were obtained from Shanghai Bioleaf Biotec (Shanghai, China). The cells were seeded at 1 × 106 cell/25 cm2 in tissue culture flasks and grown in DMEM/F12 medium supplemented with 10% fetal bovine serum, 100 U/ml penicillin and 100 U/ml streptomycin for 24 hours. The cells were then morphologically differentiated into neuron-like cells by treatment with10 mM RA. Similar with previous studies , the RA-containing medium was replaced every 2 days. The cultured SH-SY5Y cells were then used for experiments 6 days after the initiation of differentiation. All of the cultures were maintained at 37 °C in a humidified atmosphere consisting of 95% air and 5% CO2.
Real-time PCR analysis
Primer sequences used for real-time PCR
cAMP accumulation assays
The differentiated SH-SY5Y cells that had been treated with morphine and/or CCK-8 for 48 h were assayed for cAMP accumulation using a LANCE™ cAMP kit (PerkinElmer). The cells were harvested with a Versene dissociation solution followed by washing with HBSS buffer. The cells were then resuspended at a concentration of 2 × 106 cells/ml in stimulation buffer (HBSS 1×, containing 5 mM HEPES, 0.1% BSA, 0.05 mM IBMX). The Alexa pluor®647 labeled antibodies were added to the final cell suspension, and then naloxone was added to the cell suspension to precipitate the cAMP overshoot. After incubation at 37 °C for 15 min, the Detection Mix was added to the mixture. The sample was further incubated for 1 h, and was read on a TECAN instrument (Infinitie F200, Tecan, Grodig, Austria) to measure the LANCE signal. Simultaneous to the measurement of the cell-based cAMP level, the cAMP standard curve was assayed according to the manufacturer’s instructions. The LANCE signal obtained at 665 nM can be directly used to analyse the cAMP levels. The signal at 615 nM is useful to identify dispensing or quenching problems.
The data are presented as the mean ± standard deviation (S.D.) All of the experiments were performed at least three times, each with a different culture. The statistical analyses (SPSS, v. 13.0, Chicago, USA) were performed with two-way ANOVA to evaluate the interaction between morphine and naloxone on the cAMP overshoot to estabish the cellular model of morphine dependence, and then with t-test and one-way ANOVA followed by Dunnett’s t-test for subsequent experiments. A P-value <0.05 was considered statistically significant.
This study was supported, in part, by the grants obtained from the Natural Science Foundation of China (No. 81172900, 30672355), the Applied Basic Research Key Program of Hebei Province (No. 10966911D) and the Natural Science Foundation of Hebei Province (No. C2007000826).
- Su RB, Lu XQ, Huang Y, Liu Y, Gong ZH, Wei XL, Wu N, Li J: Effects of intragastric agmatine on morphine-induced physiological dependence in beagle dogs and rhesus monkeys. Eur J Pharmacol. 2008, 587 (1–3): 155-162.PubMedView Article
- Rezayof A, Nazari-Serenjeh F, Zarrindast MR, Sepehri H, Delphi L: Morphine-induced place preference: involvement of cholinergic receptors of the ventral tegmental area. Eur J Pharmacol. 2007, 562 (1–2): 92-102.PubMedView Article
- Cesselin F: Opioid and anti-opioid peptides. Fundam Clin Pharmacol. 1995, 9 (5): 409-433. 10.1111/j.1472-8206.1995.tb00517.x.PubMedView Article
- Crawley JN, Corwin RL: Biological actions of cholecystokinin. Peptides. 1994, 15 (4): 731-755. 10.1016/0196-9781(94)90104-X.PubMedView Article
- Faris PL, Komisaruk BR, Watkins LR, Mayer DJ: Evidence for the neuropeptide cholecystokinin as an antagonist of opiate analgesia. Science. 1983, 219: 310-312. 10.1126/science.6294831.PubMedView Article
- Benoliel JJ, Mauborgne A, Bourgoin S, Legrand JC, Hamon M, Cesselin F: Opioid control of the in vitro release of cholecystokinin-like material from the rat substantia nigra. J Neurochem. 1992, 58 (3): 916-922. 10.1111/j.1471-4159.1992.tb09344.x.PubMedView Article
- Becker C, Pohl M, Thiebot MH, Collin E, Hamon M, Cesselin F, Benoliel JJ: Delta-opioid receptor-mediated increase in cortical extracellular levels of cholecystokinin-like material by subchronic morphine in rats. Neuropharmacology. 2000, 39 (2): 161-171. 10.1016/S0028-3908(99)00161-6.PubMedView Article
- DeSantana JM, da Silva LF, Sluka KA: Cholecystokinin receptors mediate tolerance to the analgesic effect of TENS in arthritic rats. Pain. 2010, 148 (1): 84-93. 10.1016/j.pain.2009.10.011.PubMed CentralPubMedView Article
- Ma KT, Si JQ, Zhang ZQ, Zhao L, Fan P, Jin JL, Li XZ, Zhu L: Modulatory effect of CCK-8S on GABA-induced depolarization from rat dorsal root ganglion. Brain Res. 2006, 1121 (1): 66-75. 10.1016/j.brainres.2006.08.094.PubMedView Article
- Van Kampen J, Frydryszak H, Stoessl AJ: Behavioural evidence for cholecystokinin-dopamine D1 receptor interactions in the rat. Eur J Pharmacol. 1996, 298 (1): 7-15. 10.1016/0014-2999(95)00767-9.PubMedView Article
- Tanganelli S, Fuxe K, Antonelli T, O'Connor WT, Ferraro L: Cholecystokinin/dopamine/GABA interactions in the nucleus accumbens: biochemical and functional correlates. Peptides. 2001, 22 (8): 1229-1234. 10.1016/S0196-9781(01)00446-6.PubMedView Article
- Phillips GD, Le Noury J, Wolterink G, Donselaar-Wolterink I, Robbins TW, Everitt BJ: Cholecystokinin-dopamine interactions within the nucleus accumbens in the control over behaviour by conditioned reinforcement. Behav Brain Res. 1993, 55 (2): 223-231. 10.1016/0166-4328(93)90118-A.PubMedView Article
- Larsson LI, Rehfeld JF: Localization and molecular heterogeneity of cholecystokinin in the central and peripheral nervous system. Brain Res. 1979, 165 (2): 201-218. 10.1016/0006-8993(79)90554-7.PubMedView Article
- Lu L, Huang M, Liu Z, Ma L: Cholecystokinin-B receptor antagonists attenuate morphine dependence and withdrawal in rats. Neuroreport. 2000, 11 (4): 829-832. 10.1097/00001756-200003200-00034.PubMedView Article
- Huang C, Hu ZP, Jiang SZ, Li HT, Han JS, Wan Y: CCK(B) receptor antagonist L365,260 potentiates the efficacy to and reverses chronic tolerance to electroacupuncture-induced analgesia in mice. Brain Res Bull. 2007, 71 (5): 447-451. 10.1016/j.brainresbull.2006.11.008.PubMedView Article
- Dourish CT, O'Neill MF, Coughlan J, Kitchener SJ, Hawley D, Iversen SD: The selective CCK-B receptor antagonist L-365,260 enhances morphine analgesia and prevents morphine tolerance in the rat. Eur J Pharmacol. 1990, 176 (1): 35-44. 10.1016/0014-2999(90)90129-T.PubMedView Article
- Rezayat M, Nikfar S, Zarrindast MR: CCK receptor activation may prevent tolerance to morphine in mice. Eur J Pharmucol. 1994, 254 (1–2): 21-26.View Article
- Wen D, Ma CL, Cong B, Zhang YJ, Yang SC, Meng YX, Yu F, Ni ZY, Li SJ: Effects of CCK-8 and its receptor antagonists given intracerebroventricularly on withdrawal symptom of morphine dependent rats. Chin Pharmacol Bull. 2011, 27 (10): 1368-1373.
- Wen D, Ma CL, Cong B, Zhang YJ, Yang SC, Yu F, Ni ZY, Li SJ: Effects of CCK-8 and its receptor antagonists on opioid receptor in prefrontal cortex, cauduate putamen and hippocampus of morphine withdrawal rats. Chin Pharmacol Bull. 2010, 26: 867-871.
- Rezayat M, Azizi N, Zarrindast MR: On the mechanism(s) of cholecystokinin (CCK): receptor stimulation attenuates morphine dependence in mice. Pharmacol Toxicol. 1997, 81 (3): 124-129. 10.1111/j.1600-0773.1997.tb00041.x.PubMedView Article
- Wank SA: Cholecystokinin receptors. Am J Physiol. 1995, 269 (5 Pt 1): G628-G646.PubMed
- Woodruff GN, Hill DR, Boden P, Pinnock R, Singh L, Hughes J: Functional role of brain CCK receptors. Neuropeptides. 1991, 19 (Suppl): 45-56.PubMedView Article
- Mannisto PT, Lang A, Harro J, Peuranen E, Bradwejn J, Vasar E: Opposite effects mediated by CCKA and CCKB receptors in behavioural and hormonal studies in rats. Naunyn Schmiedebergs Arch Pharmacol. 1994, 349 (5): 478-484. 10.1007/BF00169136.PubMedView Article
- Noble F, Roques BP: Phenotypes of mice with invalidation of cholecystokinin (CCK(1) or CCK(2)) receptors. Neuropeptides. 2002, 36 (2–3): 157-170.PubMedView Article
- Koob GF, Bloom FE: Cellular and molecular mechanisms of drug dependence. Science. 1988, 242 (4879): 715-723. 10.1126/science.2903550.PubMedView Article
- Nestler EJ: Historical review: Molecular and cellular mechanisms of opiate and cocaine addiction. Trends Pharmacol Sci. 2004, 25 (4): 210-218. 10.1016/j.tips.2004.02.005.PubMedView Article
- Charles AC, Hales TG: From inhibition to excitation: functional effects of interaction between opioid receptors. Life Sci. 2004, 76 (5): 479-485. 10.1016/j.lfs.2004.09.012.PubMedView Article
- Xia M, Guo V, Huang R, Shahane SA, Austin CP, Nirenberg M, Sharma SK: Inhibition of morphine-induced cAMP overshoot: a cell-based assay model in a high-throughput format. Cell Mol Neurobiol. 2011, 31 (6): 901-907. 10.1007/s10571-011-9689-y.PubMed CentralPubMedView Article
- Itoh S, Katsuura G, Maeda Y: Caerulein and cholecystokinin suppress beta-endorphin-induced analgesia in the rat. Eur J Pharmacol. 1982, 80 (4): 421-425. 10.1016/0014-2999(82)90089-9.PubMedView Article
- You ZB, Tzschentke TM, Brodin E, Wise RA: Electrical stimulation of the prefrontal cortex increases cholecystokinin, glutamate, and dopamine release in the nucleus accumbens: an in vivo microdialysis study in freely moving rats. J Neurosci. 1998, 18 (16): 6492-6500.PubMed
- Herranz R: Cholecystokinin antagonists: pharmacological and therapeutic potential. Med Res Rev. 2003, 23 (5): 559-605. 10.1002/med.10042.PubMedView Article
- Mitchell JM, Bergren LJ, Chen KS, Fields HL: Cholecystokinin is necessary for the expression of morphine conditioned place preference. Pharmacol Biochem Behav. 2006, 85: 787-795. 10.1016/j.pbb.2006.11.014.PubMedView Article
- Yan YX, Hu WL, Cong B, Ma CL, Ni ZY, Niu ZQ, Yu L: Expressions of μ opioid receptor and CCK receptor in rat primary hippocampal neurons and effect of chronic morphine exposure on them. J Fourth MilMed Univ. 2007, 28 (13): 1214-1217.
- Wang XJ, Fan SG, Ren MF, Han JS: Cholecystokinin-8 suppressed 3H-etorphine binding to rat brain opiate receptors. Life Sci. 1989, 45 (2): 117-123. 10.1016/0024-3205(89)90285-3.PubMedView Article
- Wang XJ, Han JS: Modification by cholecystokinin octapeptide of the binding of mu-, delta-, and kappa-opioid receptors. J Neurochem. 1990, 55 (4): 1379-1382. 10.1111/j.1471-4159.1990.tb03149.x.PubMedView Article
- Moran TH, Schwartz GJ: Neurobiology of cholecystokinin. Crit Rev Neurobiol. 1994, 9 (1): 1-28.PubMed
- Pommier B, Beslot F, Simon A, Pophillat M, Matsui T, Dauge V, Roques BP, Noble F: Deletion of CCK2 receptor in mice results in an upregulation of the endogenous opioid system. J Neurosci. 2002, 22 (5): 2005-2011.PubMed
- Dauge V, Sebret A, Beslot F, Matsui T, Roques BP: Behavioral profile of CCK2 receptor-deficient mice. Neuropsychopharmacology. 2001, 25 (5): 690-698. 10.1016/S0893-133X(01)00291-3.PubMedView Article
- Mercer LD, Beart PM: Histochemistry in rat brain and spinal cord with an antibody directed at the cholecystokininA receptor. Neurosci Lett. 1997, 225 (2): 97-100. 10.1016/S0304-3940(97)00197-3.PubMedView Article
- Voigt JP, Huston JP, Voits M, Fink H: Effects of cholecystokinin octapeptide (CCK-8) on food intake in adult and aged rats under different feeding conditions. Peptides. 1996, 17 (8): 1313-1315. 10.1016/S0196-9781(96)00230-6.PubMedView Article
- Alttoa A, Harro J: Effect of CCK1 and CCK2 receptor blockade on amphetamine-stimulated exploratory behavior and sensitization to amphetamine. Eur Neuropsychopharmacol. 2004, 14 (4): 324-331. 10.1016/j.euroneuro.2003.09.006.PubMedView Article
- Lu L, Huang M, Ma L, Li J: Different role of cholecystokinin (CCK)-A and CCK-B receptors in relapse to morphine dependence in rats. Behav Brain Res. 2001, 120 (1): 105-110. 10.1016/S0166-4328(00)00361-2.PubMedView Article
- Noble F, Roques BP: The role of CCK2 receptors in the homeostasis of the opioid system. Drugs Today (Barc). 2003, 39 (11): 897-908. 10.1358/dot.2003.39.11.799467.View Article
- Wen D, Cong B, Ma C, Yang S, Yu H, Ni Z, Li S: The effects of exogenous CCK-8 on the acquisition and expression of morphine-induced CPP. Neurosci Lett. 2012, 510 (1): 24-28. 10.1016/j.neulet.2011.12.063.PubMedView Article
- Doi T, Jurna I: Analgesic effect of intrathecal morphine demonstrated in ascending nociceptive activity in the rat spinal cord an in effectiveness of caerulein and cholecystokinin octapeptide. Brain Res. 1982, 234 (2): 399-407. 10.1016/0006-8993(82)90879-4.PubMedView Article
- Wen D, Ma CL, Cong B, Yu HL, Yu F, Ni ZY, Li SJ: Interaction of CCK-8 and endogenous opioid system in the opioid dependence. Chin Pharmacol Bull. 2010, 26 (11): 421-426.
- Heinricher MM, Neubert MJ: Neural basis for the hyperalgesic action of cholecystokinin in the rostral ventromedial medulla. J Neurophysiol. 2004, 92 (4): 1982-1989. 10.1152/jn.00411.2004.PubMedView Article
- Hadjiivanova C, Belcheva S, Belcheva I: Cholecystokinin and learning and memory processes. Acta Physiol Pharmacol Bulg. 2003, 27 (2–3): 83-88.PubMed
- Zhang W, Segura BJ, Mulholland MW: Cholecystokinin-8 induces intracellular calcium signaling in cultured myenteric neurons from neonatal guinea pigs. Peptides. 2002, 23 (10): 1793-1801. 10.1016/S0196-9781(02)00136-5.PubMedView Article
- Lankisch TO, Tsunoda Y, Lu Y, Owyang C: Characterization of CCK(A) receptor affinity states and Ca(2+) signal transduction in vagal nodose ganglia. Am J Physiol Gastrointest Liver Physiol. 2002, 282 (6): G1002-G1008.PubMedView Article
- Mitchell VA, Jeong HJ, Drew GM, Vaughan CW: Cholecystokinin exerts an effect via the endocannabinoid system to inhibit GABAergic transmission in midbrain periaqueductal gray. Neuropsychopharmacology. 2012, 36 (9): 1801-1810.View Article
- Yasui M, Kawasaki K: CCKB-receptor activation augments the long-term potentiation in guinea pig hippocampal slices. Jpn J Pharmacol. 1995, 68 (4): 441-447. 10.1254/jjp.68.441.PubMedView Article
- Fang F, Cao Q, Song F, Liu J: Effects of long-term morphine exposure on the cAMP system and c-Fos phosphorylation in differentiated SH-SY5Y cells. Zhongguo Yi Xue Ke Xue Yuan Xue Bao. 1999, 21 (4): 262-267.PubMed
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.