八肽胆囊收缩素对抗mu和Kappa型受体介导的镇痛作用

以往的资料表明,八肽胆襄收缩素(CCK-8)能对抗阿片镇痛,本实验进一步分析 CCK-8对抗哪一类型阿片受体激动剂的镇痛作用。给大鼠脊髓蛛网膜下腔(I.T.)注射 CCK-8(剂量4ng到1.0μg)既不产生痛敏也不产生镇痛。I.T.注射特异性的μ受体激动剂 PL01710 ng 或 k 受体激动剂 NDA P500 ng 引起的镇痛作用可被注射 CCK-8 4ng 所对抗。而L.T.注射δ受体激动剂 DPDPE(6.5,13.0和26.Oμg)引起的镇痛作用不能被 CCK-8(4ng,40ng I.T.)所对抗。但 CCK-8对抗 PL017和 NDAP 镇痛的作用可被 I.T.CCK 受体拮抗剂 proglumide(3μg)所翻转。以上结果表明,I.T.注射 CCK-8可有效地对抗μ和 k 受体介导的镇痛,并且这种对抗作用是经 CCK 受体介导而实现的。     

Effects of exogenous cholecystokinin octapeptide on acquisition of naloxone precipitated withdrawal induced conditioned place aversion in rats

Cholecystokinin octapeptide (CCK-8), a gut-brain peptide, regulates a variety of physiological behavioral processes. Previously, we reported that exogenous CCK-8 attenuated morphine-induced conditioned place preference, but the possible effects of CCK-8 on aversively motivated drug seeking remained unclear. To investigate the effects of endogenous and exogenous CCK on negative components of morphine withdrawal, we evaluated the effects of CCK receptor antagonists and CCK-8 on the naloxone-precipitated withdrawal-induced conditioned place aversion (CPA). The results showed that CCK2 receptor antagonist (LY-288,513, 10 μg, i.c.v.), but not CCK1 receptor antagonist (L-364,718, 10 μg, i.c.v.), inhibited the acquisition of CPA when given prior to naloxone (0.3 mg/kg) administration in morphine-dependent rats. Similarly, CCK-8 (0.1-1 μg, i.c.v.) significantly attenuated naloxone-precipitated withdrawal-induced CPA, and this inhibitory function was blocked by co-injection with L-364,718. Microinjection of L-364,718, LY-288,513 or CCK-8 to saline pretreated rats produced neither a conditioned preference nor aversion, and the induction of CPA by CCK-8 itself after morphine pretreatments was not significant. Our study identifies a different role of CCK1 and CCK2 receptors in negative affective components of morphine abstinence and an inhibitory effect of exogenous CCK-8 on naloxone-precipitated withdrawal-induced CPA via CCK1 receptor.     

Effects of amylin on feeding of goldfish: interactions with CCK

In mammals, amylin (AMY) is a peptide that is secreted from the pancreas in response to a meal. AMY inhibits food intake and may also contribute to the anorectic effects of the brain-gut peptide cholecystokinin (CCK). In this study, we assessed the role of AMY in the regulation of food intake in goldfish (Carassius auratus) and its interactions with CCK. Fish were injected intraperitoneally (i.p.) with mammalian AMY and intracerebroventricularly (i.c.v.) with mammalian AMY, alone or in combination with the sulfated octapeptide CCK-8S. We also assessed the effects of i.c.v. injections of AC187, an amylin receptor antagonist on the central actions of both AMY and CCK-8S, as well as the effects of i.c.v. injections of proglumide, a CCK receptor antagonist, on the central effects of AMY. AMY injected i.p. at 100 ng/g but not 25 or 50 ng/g or i.c.v. at 10 ng/g but not 1 ng/g significantly decreased food intake as compared to saline-treated fish. Fish co-treated i.c.v. with AMY at 1 ng/g and CCK-8S at 1 ng/g had a food intake lower than that of control fish and fish treated with either 1 ng/g CCK-8S or 1 ng/g AMY, suggesting a synergy between the two systems. Whereas low i.c.v. doses of AC187 (30 ng/g) had no effect, moderate doses (50 ng/g) induced an increase in food intake, indicating a role of endogenous AMY in satiety in goldfish. Blocking central amylin receptors with i.c.v. AC187 (30 ng/g) resulted in an inhibition of both i.c.v. AMY- and CCK-induced reduction in feeding. Blocking central CCK receptors with i.c.v. proglumide (25 ng/g) resulted in an inhibition of both i.c.v. CCK-induced and AMY-induced decrease in food intake. Our results show for the first time in fish that AMY is a potent anorexigenic factor and that its actions are interdependent with those of CCK.     

Central administration of neuropeptide FF and related peptides attenuate systemic morphine analgesia in mice

Neuropeptide FF (NPFF) belongs to an opioid-modulating peptide family. NPFF has been reported to play important roles in the control of pain and analgesia through interactions with the opioid system. However, very few studies examined the effect of supraspinal NPFF system on analgesia induced by opiates administered at the peripheral level. In the present study, intracerebroventricular (i.c.v.) injection of NPFF (1, 3 and 10 nmol) dose-dependently inhibited systemic morphine (0.12 mg, i.p.) analgesia in the mouse tail flick test. Similarly, i.c.v. administration of dNPA and NPVF, two agonists highly selective for NPFF(2) and NPFF(1) receptors, respectively, decreased analgesia induced by i.p. morphine in mice. Furthermore, these anti-opioid activities of NPFF and related peptides were blocked by pretreatment with the NPFF receptors selective antagonist RF9 (10 nmol, i.c.v.). These results demonstrate that activation of central NPFF(1) and NPFF(2) receptors has the similar anti-opioid actions on the antinociceptive effect of systemic morphine.     

CCK-8 Inhibits Acute Morphine-induced Spatial Reference Memory Impairment in Mice

Administration of morphine may impair learning and memory processes. Cholecystokinin has been reported to be involved in various types of memory, and our previous study found that Cholecystokinin octapeptide attenuates spatial memory impairment in chronic morphine-treated mice. However, the effect of CCK-8 on acute morphine-induced memory impairment is not clear. In this study, effect of acute CCK-8 and morphine on spatial reference memory was evaluated using Morris water maze in KM mice. Acetylcholine (Ach) content was measured using ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC–MS/MS). Pre-training with morphine (5, 10 mg/kg, i.p.) significantly impaired spatial reference memory acquisition without disturbing the performance in the visible platform task, while pre-test morphine has no effect on memory retrieval. Pre-training (0.01, 0.1 and 1 μg, i.c.v.) or pre-test (0.1 and 1 μg, i.c.v.) of CCK-8 facilitated spatial reference memory acquisition and retrieval, respectively. CCK-8 (0.1 and 1 μg) significantly attenuated memory loss by pre-training morphine. Furthermore, CCK-8 (1 μg, i.c.v) increased acetylcholine contents of hippocampus in saline or morphine-treated mice. Our study identifies CCK-8 reversed spatial reference memory loss induced by acute morphine, and the mnemonic effect could be related to the facilitation of CCK-8 on memory acquisition and retrieval through accelerating acetylcholine release in hippocampus.     

Attenuation of systemic morphine-induced analgesia by central administration of ghrelin and related peptides in mice

Ghrelin, an acylated 28-amino peptide secreted in the gastric endocrine cells, has been demonstrated to stimulate the release of growth hormone, increase food intake, and inhibit pro-inflammatory cascade, etc. Ghrelin mainly combines with its receptor (GHS-R1α) to play the role in physiological and pathological functions. It has been reported that ghrelin plays important roles in the control of pain through interaction with the opioid system in inflammatory pain and acute pain. However, very few studies show the effect of supraspinal ghrelin system on antinociception induced by intraperitoneal (i.p.) administration of morphine. In the present study, intracerebroventricular (i.c.v.) injection of ghrelin (0.1, 1, 10 and 100 nmol/L) produced inhibition of systemic morphine (6 mg/kg, i.p.) analgesia in the tail withdrawal test. Similarly, i.c.v. injection GHRP-6 and GHRP-2 which are the agonists of GHS-R1α, also decreased analgesia effect induced by morphine injected intraperitoneally in mice. Furthermore, these anti-opioid activities of ghrelin and related peptides were not blocked by pretreatment with the GHS-R1α selective antagonist [d-Lys³]-GHRP-6 (100 nmol/L, i.c.v.). These results demonstrated that central ghrelin and related peptides could inhibit the analgesia effect induced by intraperitoneal (i.p.) administration of morphine. The anti-opioid effects of ghrelin and related peptides do not interact with GHS-R1a. These findings may pave the way for a new strategy on investigating the interaction between ghrelin system and opioids on pain modulation.     

Different peripheral and central antagonistic activity of new glutaramic acid derivatives on satiety induced by cholecystokinin in rats

New glutaramic acid derivatives with cholecystokinin antagonistic activity were evaluated for their capacity to inhibit the satiety effect induced in the rat by intraperitoneal (i.p.) injection of cholecystokinin octapeptide (CCK-8). The most active compound, CR 1409, is about 4000 times more potent than proglumide when injected peripherally (i.p.). This compound competitively inhibits the action of CCK-8 at the receptor responsible for the satiety effect. In contrast, CR 1409, i.p. or intracerebroventricularly (i.c.v.) injected does not exhibit antagonistic effects when CCK-8 is administered i.c.v., confirming the existence of at least two different populations of CCK receptors.     

Morphine-3-glucuronide--a potent antagonist of morphine analgesia

In this study, morphine-3-glucuronide (M3G), the major plasma and urinary metabolite of morphine, was shown to be a potent antagonist of morphine analgesia when administered to rats by the intra-cerebroventricular (i.c.v.) route. The antagonism of morphine analgesia was observed irrespective of whether i.c.v. M3G (2.5 or 3.0 micrograms) was administered 15 mins prior to or 15 mins after i.c.v. morphine (20 micrograms). When M3G (10mg) was administered intraperitoneally (i.p.) to rats 30-40 mins prior to morphine (1.5mg i.p.), the analgesic response was significantly reduced compared to administration of morphine (1.5mg i.p.) alone. It was further demonstrated that i.c.v. M3G (2.0 micrograms) antagonized the analgesic effects of subsequently administered i.c.v. morphine-6-glucuronide (0.25 micrograms).     

八肽胆囊收缩素对家兔内毒素休克时肺动脉张力的影响

为探讨八肽胆囊收缩素(CCK-8)缓解内毒素休克(ES)时肺动脉血压(PAP)增高的机制,观察了CCK-8对脂多糖(LPS)引起家兔ES时PAP变化以及离体肺动脉环(PARs)张力改变的影响。实验用新西兰大耳白雄性家兔40只,分为颈静脉注入LPS(8mg／kg i．v.)复制的家兔ES模型、LPS注入前15min给CCK-8(15μg/kg,i.v.)、LPS注入前15min给CCK受体拮抗剂丙谷胺(Pro 1mg／kg,i.v.)、单独注入CCK-8(15μg/kg,i.v.)和注射生理盐水(对照)共5组。用生理记录仪监测平均动脉压(MAP)和PAP的变化;5h后制备PARs,应用血管张力测定技术,检测各组PARs张力。结果为：(1)ES时MAP降低、PAP升高,CCK-8可完全翻转ES时PAP的增高,而Pro加剧ES时PAP的增高;(2)LPS组的PARs对苯肾上腺素(PE)的收缩反应增强,对ACh内皮依赖性舒张反应降低,而CCK-8可逆转LP5的上述作用。上述结果提示CCK—8可缓解ES时的PAP升高,这可能与其调节肺动脉张力改变有关。     

A new simple mouse model for the in vivo evaluation of cholecystokinin (CCK) antagonists: comparative potencies and durations of action of nonpeptide antagonists

A new simple mouse assay for the in vivo evaluation of CCK antagonists which is based upon visual determination of the gastric emptying of a charcoal meal is described. CCK-8 (24 micrograms/kg s.c.) but not various other peptide and nonpeptide agents effectively inhibited gastric emptying in this test system. The effect of CCK-8 was antagonized by established peripheral CCK antagonists but not representative agents of various other pharmacological classes. The rank order of potency of the CCK antagonists were: L-364,718 (ED50 = 0.01 mg/kg, i.v.; 0.04 mg/kg, p.o.) greater than Compound 16 (ED50 = 1.5 mg/kg, i.v.; 2.0 mg/kg p.o.) greater than asperlicin (ED50 = 14.8 mg/kg i.v.) greater than proglumide (ED50 = 184 mg/kg i.v.; 890 mg/kg, p.o.). Duration of action studies based upon ED50 values determined at various time intervals after oral administration showed that L-364,718 and proglumide are considerably longer acting than Compound 16. Asperlicin (ED50 greater than 300 mg/kg, p.o.) was ineffective as a CCK antagonist when administered orally. These data provide the first direct comparisons of the in vivo potencies of current CCK antagonists and demonstrate the utility of a new simple mouse assay for the in vivo characterization of peripheral CCK antagonists.