Orphanin FQ/nociceptin analgesia in the rat

The heptadecapeptide orphanin FQ or nociceptin (OFQ/N), the endogenous ligand for the orphan opioid receptor, has a complex pharmacology in mice, eliciting either an anti-opioid/hyperalgesic action or analgesia depending upon the dose and testing paradigm. Unlike mice, orphanin FQ/nociceptin fails to elicit hyperalgesia in the rat following intracerebroventricular injection. Both OFQ/N and a truncated version, OFQ/N(1-11), produce a robust analgesic response. OFQ/N analgesia is readily antagonized by the opioid antagonists naloxone or diprenorphine, despite their very poor affinity for the cloned orphan opioid receptor. Antisense studies revealed that probes targeting the second and third coding exon of the orphan clone significantly attenuate OFQ/N analgesia, while the exon 1 probe was inactive. These results indicate that OFQ/N elicits a naloxone-sensitive analgesia in rats similar to that previously reported in mice.     

The novel neuropeptide orphanin FQ fails to produce conditioned place preference or aversion

An unbiased conditioned place preference procedure was used to determine whether the newly-identified neuropeptide orphanin FQ produced motivational effects after intracerebroventricular microinjections. Microinjections of orphanin FQ (0.1–100 nmol) failed to produce conditioned place preference or aversion, but a pronounced motor impairment was observed during conditioning sessions with the two highest doses. Thus, it appears that orphanin FQ lacks motivational effects when administered at behaviourally active doses.     

Orphanin FQ stimulates prolactin and growth hormone release in male and female rats

Intracerebroventricular administration of Orphanin FQ (5.5, 55 or 550 pmol) caused a dose-related increase in prolactin secretion in both male and female rats and stimulated GH secretion in males. The magnitude of the prolactin secretory response was greater in females than in males. These effects of OFQ on prolactin and growth hormone release are the same as the stimulatory effects of the endogenous opioid peptides.     

抑郁症患者血浆孤啡肽含量研究

目的为探讨抑郁症的可能病因,对抑郁症患者血浆孤啡肽(OFQ)含量进行了对照研究。方法抽取29例抑郁症患者和24例正常人的静脉血,用放射免疫(RIA)的方法分别测其血浆中OFQ含量,比较抑郁症患者和正常人血浆OFQ含量有无差异,抑郁症患者OFQ含量与汉密顿抑郁量表(HAMD)评分的相关性,及抑郁症患者血浆OFQ含量的影响因素。结果与正常人比较,抑郁症组OFQ含量明显升高(t=8．70,P＜0．0001)；OFQ含量与HAMD评分呈正相关(r=0．63,P＜0．01)；OFQ含量主要与抑郁情绪、夸大、失眠、自卑感、自杀、强迫症状、教育水平、关注身体健康等因素相关,而年龄、性别、职业、病程、曾用药等其他因素与OFQ含量无明显相关。结论通过测量血浆OFQ含量可作为抑郁症诊断的参考指标。     

Central administration of Orphanin FQ inhibits GnRH secretion by ORL1 receptor in the median eminence of freely moving ovariectomized rats

Objective

This study aimed to investigate the possible role of Orphanin FQ (OFQ) in the regulation of hypothalamic gonadotropin-releasing hormone (GnRH) secretion.

Methods

The method of push-pull perfusion and radioimmunoassay (RIA) were adopted to examine the secretory profile of GnRH in the median eminence (ME) in freely moving ovariectomized (OVX) rats after intracerebroventricular (icv) injection of OFQ and/or [Nphe¹]NC(1–13)NH² (NC13), a competitive antagonists of the opioid receptor-like 1 receptor (ORL1 receptor).

Results

GnRH release from ME significantly decreased from 40 min to 80 min after the administration of 20 and 200 nmol OFQ in OVX rats (P< 0.05). This inhibitory effect of 20 nmol OFQ could be abolished by pretreatment with equal dose of NC13. More interestingly, GnRH secretion from ME was increased markedly 60 min after icv injection of 100 and 200 nmol NC13 (P < 0.05).

Conclusion

Our results suggested central administration of OFQ could inhibit the release of GnRH in the ME of hypothalamus through ORL1 receptor, providing further in vivo evidence supporting the role of OFQ in the control of GnRH secretion.     

产后抑郁症与孤啡肽及单胺类递质的相关性研究

目的　探讨孤啡肽 (OFQ)及单胺类递质与产后抑郁症的关系。方法　采用放射免疫法测定 2 5名健康产妇 (对照组 )及 17例产后抑郁症妇女 (抑郁组 )静脉血中孤啡肽及单胺类递质含量。结果　①抑郁组及对照组血孤啡肽含量分别为 (2 7 39± 6 0 4 )ng/L及 (10 37± 3 6 5 )ng/L ,与对照组相比 ,抑郁组孤啡肽含量显著升高 (P <0 0 1) ;抑郁组及对照组血 5 羟色胺 (5 HT)含量分别为 (0 93± 0 2 1) μmol/L及 (1 4 3± 0 36 ) μmol/L ,二者间有显著差异 (P <0 0 5 ) ;抑郁组血多巴胺 (DA)含量为 (2 15± 0 4 1) μmol/L ,显著低于对照组 (P <0 0 5 )。②抑郁组孤啡肽与5 HT及DA含量呈显著负相关 (r为 0 6 0 1及 0 5 93,P <0 0 5 )。③抑郁组爱丁保产后抑郁量表总分 (EPDS)与OFQ含量呈显著正相关 (r为 0 5 12 ,P <0 0 5 ) ,与 5 HT、DA含量呈显著负相关 (r分别为 - 0 5 71及 - 0 5 2 6 ,P <0 0 5 )。结论　孤啡肽与产后抑郁症的发生发展密切相关。     

血浆孤啡肽水平与抑郁障碍的相关性研究

目的探讨抑郁障碍患者血浆孤啡肽（OFQ）水平的变化。方法应用放射免疫（RIA）法分别测定24例抑郁患者和31例正常人血浆OFQ的浓度。结果 1．与对照组相比，抑郁组血浆OFQ水平明显增高（t=2．76，P〈0．01），差异有统计学意义。2．抑郁组0FQ含量与HAMD、MADRS总分呈显著正相关（P〈0．01）。结论血浆OFQ水平的变化可能参与抑郁障碍的发病机制，并可能提示病情的严重程度。     

Orphanin FQ/nociceptin binds to functionally coupled ORL1 receptors on human immune cell lines and alters peripheral blood mononuclear cell proliferation

Orphanin FQ/nociceptin (OFQ/N) has been shown to modulate nociception, responses to stress and anxiety. We investigated OFQ/N function in human immune cells. We find that monocytic U937, T lymphocytic CEM, and MOLT-4 cell lines express OFQ/N binding sites at levels comparable to that of human SH-SY5Y neuroblastoma cells. We show that OFQ/N receptors are functionally coupled to G proteins in these cells. Finally OFQ/N decreases proliferation of phytohemagglutinin-stimulated peripheral blood mononuclear cells in vitro at doses ranging from 10(-13) to 10(-8) M. Thus, our data suggest that OFQ/N and OFQ/N receptor may act as an immunomodulatory system.     

内囊出血大鼠血浆及心肌组织孤啡肽、垂体腺苷酸环化酶激活肽水平的变化

目的研究内囊出血大鼠血浆及心肌组织中孤啡肽、垂体腺苷酸环化酶激活肽(PACAP)含量变化及其在急性心肌损害中的作用。方法建立大鼠内囊出血模型,用放免法测定血浆及心肌组织中孤啡肽、PACAP含量。结果大鼠内囊出血组血浆及心肌组织中孤啡肽含量明显高于对照组(P<0.01);血浆PACAP含量明显高于对照组(P<0.01),而心肌组织中PACAP含量明显低于对照组(P<0.01)。结论孤啡肽、PACAP含量变化在内囊出血后急性心肌损害过程中起重要作用。     

Orphanin FQ inhibits synaptic transmission and long-term potentiation in rat hippocampus

It is known that opioid peptides acting on opioid receptors can modulate hippocampal synaptic functions. Although a novel member of the opioid receptor family, ORL₁ receptors, that displays high-sequence homology with classical opioid receptors is abundant in the hippocampus, little is known regarding its role in synaptic function. The present study was designed to investigate whether activation of the ORL₁ receptor by its natural ligand, orphanin FQ, could modulate synaptic transmission and synaptic plasticity in the hippocampus. The actions of orphanin FQ in the CA1 and dentate gyrus were examined by field potential recordings in response to stimulation of Schaffer collaterals and perforant path, respectively. Our results showed that orphanin FQ, but not the inactive analog des-Phe¹-orphanin FQ, reduced both the slope of the excitatory postsynaptic potentials and population spike amplitude. The inhibitory effect of orphanin FQ is dose dependent and probably involves a presynaptic mechanism, as suggested by the significantly increased paired-pulse facilitation evoked in the presence of orphanin FQ. In addition, orphanin FQ was found to inhibit the induction of long-term potentiation at the Schaffer collateral-CA1 synapse. These results demonstrate that orphanin FQ can function as an inhibitory modulator regulating synaptic transmission and synaptic plasticity in the hippocampus, suggesting that activation of ORL₁ receptors may play an important role in synaptic plasticity involved in learning and memory. Hippocampus 7:88–94, 1997. © 1997 Wiley-Liss, Inc.     

Effects of melatonin on orphanin FQ/nociceptin-induced hyperalgesia in mice

The pain modulatory properties of melatonin (MT) are generally recognized but the detail of the interaction between melatonin and opioid system in pain regulation is not fully understood. The present study was undertaken to investigate the modulatory effect of melatonin (MT) on the hyperalgesic effect of Orphanin FQ/Nociceptin (OFQ/NC, NC), a member of opioid peptide family. Intracerebroventricular (i.c.v.) administration of NC (10 microg/mouse) induced significant hyperalgesic effect in tail-flick test in mice; i.c.v. (5, 10, 50 microg/mouse) or intraperitoneal (i.p.) (5, 10, 50 mg/kg) co-injection of melatonin dose-dependently reversed NC-induced hyperalgesia and showed a profound analgesic effect. The antihyperalgesia effect of MT could be significantly antagonized by i.c.v. co-injection of luzindole (10 microg/mouse) (an antagonist of MT receptor) or naloxone (10 microg/mouse) (antagonist of traditional opioid receptor). Taken together, all the results suggested that MT could produce a luzindole and naloxone sensitive reversing effect on NC-induced hyperalgesia at supraspinal and peripheral level in mice. The augmentation effect of MT on the traditional opioid system may be one of the mechanisms of this antihyperalgesia action induced by MT. The present work will help to elucidate the mechanism of the pain modulation effect of MT, and also will help to represent new interesting modulating therapeutic targets for the relief of pain.     

内囊出血大鼠血浆及心肌孤啡肽水平变化研究

目的研究内囊出血大鼠血浆及心肌组织匀浆中孤啡肽含量变化及在急性心肌损害中的作用.方法通过建立大鼠内囊出血模型,用放免法(RIA)测定血浆及心肌组织匀浆中孤啡肽含量.结果大鼠内囊出血组血浆及心肌组织匀浆中孤啡肽含量明显高于对照组(P<0.01).结论孤啡肽含量变化在内囊出血后急性心肌损害过程中起重要作用.     

焦虑症的社会支持和防御方式的对照研究

目的 探讨焦虑症患者应激状态、社会支持和防御方式的特点。方法 采用汉密尔顿焦虑量表、工作生活环境调查表、社会支持调查表的防御方式问卷,对36名焦虑症患者进行测试,并与36名正常人做对照研究。结果 （1）焦虑症组的社会支持满意度明显低于对照组（P＜0．01）,社会支持内容排序与对照组相比,“朋友”项的选择提前至第二位,首选“谁也没有”项达25人次;（2）心理防御方式与对照组相比有显著差异,中间型和不成熟型防御因子分高（P＜0．01）,投射、潜意显现、抱怨、幻想、退行、假性利他、伴无能之全能、隔离、交往倾向、反作用形成、期望因子分高（P＜0．01或P＜0．05）,压抑因子分低（P＜0．01）;（3）生活事件数与平均应激强度与对照组相比无明显差异（P＞0．05）。结论 （1）焦虑症患者的社会支持系统满意度差,且防御方式存在明显的不成熟倾向;（2）焦虑症的发生与社会支持系统的缺乏和防御方式的不成熟有关。     

Accelerated release and production of orphanin FQ in brain of chronic morphine tolerant rats

Orphanin FQ has been shown to possess anti-opioid activity at supraspinal level. Our previous work revealed that chronic morphine tolerance could be reversed by intracerebroventricular (i.c.v.) injection of OFQ IgG to rats. In this study, we used radioimmunoassay (RIA) to assess the changes of Orphanin FQ immunoreactivity (OFQ-ir) in cerebroventricular perfusate, periaqueductal gray (PAG) and amygdala of rats made tolerance to morphine (10-60 mg/kg, s.c., t.i.d., for 5 days). The results indicated that: (1) In rats administrated with morphine for 3 and 5 days, the content of OFQ-ir in cerebroventricular perfusate increased by 25% and 52% over the NS control group. (2) The content of OFQ-ir in PAG of rats receiving 1d, 3d and 5d injections of morphine showed an increase of 17%, 48% and 81% respectively over NS group. (3) The content of OFQ-ir in amygdala of rats given 3d and 5d of morphine showed a 36% and 55% increase compared with corresponding control group. It is suggested that continuous use of high doses of morphine accelerated the release and biosynthesis of OFQ in rat brain to antagonize the effect of opioids, which may play a role in the development of morphine tolerance, and that brain OFQ may serve as a delayed negative feedback control on opioid analgesia.     

Effects of orphanin FQ on endomorphin-1 induced analgesia

Orphanin FQ (also known as nociceptin) is a 17-amino-acid peptide which acts as a potent endogenous agonist of the orphan opioid receptor-like (ORL1) receptor. Endomorphin-1, a 4-amino-acid peptide discovered recently, is a potent and selective endogenous agonist for the mu-opiate receptor. In the present study, the effect of OFQ or/and endomorphin-1 on the response to noxious thermal stimuli was observed using the tail-flick test in rats. Intracerebroventricular (i.c.v.) administration of OFQ (1, 5 microg) could shorten tail-flick latency; In contrast, intrathecal (i.t.) administration of OFQ (1, 2 or 10 microg) could increase the latency; i.c.v. (1, 2, 5 microg) or i.t. (0.2, 2, 5 microg) administration of endomorphin-1 dose-dependently increased the latency, indicating an analgesic effect. Furthermore, OFQ (0.1-5 microg) when intraventricularly injected together with endomorphin-1 (5 microg), could dose-dependently reverse the analgesia induced by the latter. On the contrary, OFQ (1 microg) intrathecally injected together with endomorphin-1 (0.2 microg) could further increase the tail-flick latency. The results showed that OFQ at the supraspinal level produces hyperalgesia and is antagonistic to endomorphin-1, while at the spinal level it produces analgesia and is synergic with endomorphin-1. Different interaction mechanism between OFQ and endomorphin-1 in the brain and the spinal cord is thus suggested.     

Gonadal Steroids Differentially Modulate the Actions of Orphanin FQ/Nociceptin at A Physiologically Relevant Circuit Controlling Female Sexual Receptivity

Orphanin FQ/nociceptin (OFQ/N) inhibits the activity of pro‐opiomelanocortin (POMC) neurones located in the hypothalamic arcuate nucleus (ARH) that regulate female sexual behaviour and energy balance. We tested the hypothesis that gonadal steroids differentially modulate the ability of OFQ/N to inhibit these cells via presynaptic inhibition of transmitter release and postsynaptic activation of G protein‐gated, inwardly‐rectifying K⁺ (GIRK)‐1 channels. Whole‐cell patch clamp recordings were performed in hypothalamic slices prepared from ovariectomised rats. OFQ/N (1 μm ) decreased the frequency of miniature excitatory postsynaptic currents (mEPSCs) and miniature inhibitory postsynaptic currents (mIPSCs), and also caused a robust outward current in the presence of tetrodotoxin, in ARH neurones from vehicle‐treated animals. A priming dose of oestradiol benzoate (EB; 2 μg) increased basal mEPSC frequency, markedly diminished both the OFQ/N‐induced decrease in mEPSC frequency and the activation of GIRK‐1 currents, and potentiated the OFQ/N‐induced decrease in mIPSC frequency. Steroid treatment regimens that facilitate sexual receptivity reinstate the basal mEPSC frequency, the OFQ/N‐induced decrease in mEPSC frequency and the activation of GIRK‐1 currents to levels observed in vehicle‐treated controls, and largely abolish the ability of OFQ/N to decrease mIPSC frequency. These effects were observed in an appreciable population of identified POMC neurones, almost one‐half of which projected to the medial preoptic nucleus. Taken together, these data reveal that gonadal steroids influence the pleiotropic actions of OFQ/N on ARH neurones, including POMC neurones, in a disparate manner. These temporal changes in OFQ/N responsiveness further implicate this neuropeptide system as a critical mediator of the gonadal steroid regulation of reproductive behaviour.     

UFP‐112 a Potent and Long‐Lasting Agonist Selective for the Nociceptin/Orphanin FQ Receptor

Nociceptin/orphanin FQ (N/OFQ) controls several biological functions via selective activation of the N/OFQ peptide receptor (NOP). [(pF)Phe⁴Aib⁷Arg¹⁴Lys¹⁵]N/OFQ‐NH₂ (UFP‐112) is an NOP receptor ligand designed using a combination of several chemical modifications in the same peptide sequence that increase NOP receptor affinity/potency and/or reduce susceptibility to enzymatic degradation. In the present review article, we summarize data from the literature and present original findings on the in vitro and in vivo pharmacological features of UFP‐112. Moreover, important biological actions and possible therapeutic indications of NOP receptor agonists are discussed based on the results obtained with UFP‐112 and compared with other peptide and nonpeptide NOP receptor ligands.     

Roles of the bed nucleus of stria terminalis and of the amygdala in N/OFQ-mediated anxiety and HPA axis activation

Nociceptin/orphanin FQ (N/OFQ) is an opioid-related neuropeptide that is widely distributed in limbic regions of the brain. After intracerebroventricular (icv) injections in rodents, N/OFQ produces elevations in hypothalamic-pituitary-adrenal (HPA) axis activity, and has been reported to produce both anxiogenic and anxiolytic actions. We examined the neuroanatomical basis of these effects with injections of N/OFQ (0.01-1.0nmol) into the lateral ventricle, the amygdala, and the bed nucleus of stria terminalis (BNST) in independent groups of well-handled rats under low stress conditions. Anxiety-related behaviors were evaluated in a neophobic test of anxiety. The latency to enter, total time spent in, and number of entries into an unfamiliar open field and its central zone were measured. After the open field testing, plasma samples were obtained for analysis of HPA axis activity. The N/OFQ-treated rats displayed more anxiety-related behaviors than vehicle-treated rats did with all three of the injection types. However, these effects were greater and more consistent after the icv injections (0.01-1.0nmol) than they were after the amygdala (0.10-1.0nmol) or BNST (1.0nmol) injections. The icv and BNST injections also produced elevations in circulating corticosterone, indicating that the HPA axis was activated in these rats. Intra-amygdaloid injections did not affect corticosterone levels during the open field testing. These results indicate that the amygdala and BNST participate in the anxiogenic behavioral effects of N/OFQ. However, since the most potent effects were seen after icv N/OFQ injections, the anxiogenic and HPA axis-activating effects of N/OFQ appear to occur through additive actions in multiple limbic (and perhaps cortical and brainstem) sites.