1,4-Dioxolane-triazaspirodecanone derivatives as nociceptin/orphanin FQ receptor ligands

A series of N-substituted analogs based upon the spiropiperidine core of the lead compound Spiroxatrine was synthesized. In particular, the new compounds were obtained by replacing the benzodioxane moiety of the Spiroxatrine with several 2-substituted 1,3-dioxolanes. Thus the designed derivatives were synthesized and evaluated as possible NOP receptor ligands. As a conclusion of these studies, the new triazaspirodecanone derivatives showed unique and significant SAR as NOP receptor agonists. In particular, the present study demonstrated that 1-phenyl-1,3,8-triazaspiro[4.5]decan-4-one portion together with appropriate 1,3-dioxolane substituents could lead to a new promising class of NOP receptor ligands.     

Antidepressant- and anxiolytic-like effects of nociceptin/orphanin FQ receptor ligands

Many studies point toward the nociceptin/orphanin FQ (N/OFQ) and the N/OFQ peptide receptor (NOP) as targets for the development of innovative drugs for treating affective disorders. It has been reported that the activation of NOP receptors produces anxiolytic-like effects in rodents in a large series of behavioral assays, i.e., elevated plus maze, light-dark aversion, operant conflict, fear-potentiated startle, pup ultrasonic vocalizations, and hole board tests. In contrast, the blockade of N/OFQ signaling obtained with NOP-selective antagonists promotes antidepressant-like effects in the forced swimming and tail suspension tests. In these assays, N/OFQ is inactive per se, but reverses the antidepressant-like effects of NOP antagonists. NOP receptor knockout mice show an antidepressant-like phenotype, and NOP antagonists are inactive in these animals. Thus, the activation of the NOP receptor seems to evoke anxiolytic-like effects while its blockade antidepressant-like effects. This appears to be a rather unique behavioral profile since the activation or the blockade of a given neuropeptide receptor produces, in most of the cases, both antidepressant- and anxiolytic-like effects. This particular behavioral profile, the possible mechanisms of action, and the therapeutic potential of NOP receptor ligands for the treatment of depression and anxiety disorders are discussed in this review article.     

Characterisation and comparison of novel ligands for the nociceptin/orphanin FQ receptor

Studies of nociceptin/orphanin FQ (NC) have been hampered by the paucity of available ligands with activity at the nociceptin receptor (NCR). In this study we have compared the agonist profile of NC and a novel NCR agonist, Ro65-6570, in a series of radioligand binding studies and effects on forskolin-stimulated cAMP formation in Chinese hamster ovary (CHO) cells expressing the recombinant human NCR (CHOhNCR). In addition, we report the effects of three antagonists, [Nphe1]NC(1-13)NH2, J-113397 and III-BTD, on these responses. In radioligand binding studies Ro65-6570, [Nphe1]NC(1-13)NH2, J-113397 and III-BTD displaced [3H]NC with similar pKi values (8.4-8.8). This compares with a pK(D) of 10.2 for NC in a direct saturation experiment. [Nphe1]NC(1-13)NH2 and J-113397 showed at least 100-fold selectivity over classical opioid receptors. Both NC and Ro65-6570 produced a concentration-dependent inhibition of cAMP formation with pEC50 values of 9.56+/-0.06 and 8.68+/-0.04, respectively. Maximum inhibition achieved was 100%. [Nphe1]NC(1-13)NH2, J-113397 and III-BTD produced a parallel rightward shift in the concentration-response curves to both NC and Ro65-6570 with pK(B) values of approximately 6.5, approximately 7.5 and approximately 7.7, respectively. Importantly, all three antagonists were devoid of residual agonist activity. Collectively, these data indicate the value of Ro65-6570, [Nphe1]NC(1-13)NH2, J-113397 and III-BTD in studies of the physiological role played by NC. However, due to the relatively poor selectivity of Ro65-6570 and III-BTD caution should be exercised when using tissues that co-express micro-opioid receptors.     

Effects of chronic nociceptin/orphanin FQ exposure on cAMP accumulation and receptor density in Chinese hamster ovary cells expressing human nociceptin/orphanin FQ receptors

Since the therapeutic efficacy of Li+ in the treatment of mood disorder is observed only after chronic administration, we examined whether long-term Li+ treatment with a therapeutic concentration affected the elevation of intracellular-free Ca2+ concentration ([Ca2+]i) induced by carbachol, a muscarinic receptor agonist, in 1321N1 human astrocytoma cells. Carbachol caused [Ca2+]i elevation through phosphoinositide hydrolysis in a concentration-dependent manner. Treatment of the cells with phorbol 12-myristate 13-acetate (PMA), a protein kinase C activator, for 2 min resulted in a reduction of the carbachol-induced [Ca2+]i elevation. However, PMA did not reduce the carbachol-induced [Ca2+]i elevation in cells treated with PMA for 48 h, reflecting the down-regulation of protein kinase C. Although Li+ at a therapeutic concentration (1 mM) did not affect the carbachol-induced [Ca2+]i elevation in normal cells, it potently inhibited the [Ca2+]i elevation in protein kinase C down-regulated cells. This inhibitory action of Li+ was observed in a concentration- and time-dependent manner. When protein kinase C activity was directly determined, Li+ treatment did not restore protein kinase C activity in protein kinase C down-regulated cells. [3H]Quinuclidinyl benzylate, a muscarinic receptor ligand, bound to membranes derived from normal and protein kinase C down-regulated cells with a similar Kd and Bmax, and Li+ did not affect these parameters of [3H]quinuclidinyl benzylate binding. These results indicated that Li+ at a therapeutic concentration reduced the muscarinic receptor-mediated increased in [Ca2+]i under the protein kinase C-deficient condition without affecting muscarinic receptor or protein kinase C activity.     

N- and C-terminal modifications of nociceptin/orphanin FQ generate highly potent NOP receptor ligands

Previous structure-activity studies on nociceptin/orphanin FQ (N/OFQ) identified [Phe(1)Psi(CH(2)NH)Gly(2)]N/OFQ(1-13)-NH(2) and [Nphe(1)]N/OFQ(1-13)-NH(2) as a N/OFQ peptide receptor (NOP) partial agonist and pure antagonist, respectively. The addition of fluorine to the Phe(4) or the insertion of a further pair of basic amino acids Arg(14)-Lys(15) generate potent agonists. On the basis of these findings, we combined in the N/OFQ-NH(2) template the chemical modifications Arg(14)-Lys(15) and (pF)Phe(4) that increase the agonist potency with those conferring partial agonist (Phe(1)Psi(CH(2)NH)Gly(2)) or pure antagonist (Nphe(1)) properties. Twelve peptides were synthesized and pharmacologically evaluated in Chinese hamster ovary cells expressing the human recombinant NOP and in electrically stimulated mouse vas deferens and guinea pig ileum assays. All peptides behaved as NOP ligands; the chemical modifications Arg(14)-Lys(15) and (pF)Phe(4) increased ligand affinity/potency. Peptides with the normal Phe(1)-Gly(2) peptide bond behaved as full agonists, and those with the Phe(1)Psi(CH(2)NH)Gly(2) modification behaved as partial agonists, while those with the Nphe(1) modification behaved as partial agonists or pure antagonists depending on the presence or absence of the (pF)Phe(4) modification, respectively. The full agonist [(pF)Phe(4),Arg(14),Lys(15)]N/OFQ-NH(2), the partial agonist [Phe(1)Psi(CH(2)NH)Gly(2),(pF)Phe(4),Arg(14),Lys(15)]N/OFQ-NH(2), and the pure antagonist [Nphe(1),Arg(14),Lys(15)]N/OFQ-NH(2) represent the most potent peptide ligands for NOP.     

Enhanced nicotine sensitivity in nociceptin/orphanin FQ receptor knockout mice

The opioid peptide nociceptin (orphanin FQ) has been implicated in reward, reinforcement and addiction. The current study sought evidence of a role of endogenous nociceptin in nicotine responses by studying nociceptin receptor (NOP) knockout mice. The results were: (1) NOP receptor knockout mice showed enhanced anxiety-like behavior on an elevated plus maze. Whereas nicotine (0.05-0.5 mg/kg) tended to be anxiogenic in wild-type mice, NOP receptor KO mice were resistant to this effect, though interpretation was confounded by their stronger anxiety-like behavior. (2) When presented increasing nicotine concentrations (3-50 μg/ml) in a bottle choice drinking paradigm, there were no genotype-dependent differences in nicotine preference. However, NOP receptor knockout mice consumed more 3 μg/ml nicotine solution when considered in absolute terms. (3) NOP receptor knockout mice showed stronger hypothermic responses to nicotine (1 or 2 mg/kg) administration. (4) There was modest evidence that NOP receptor KO mice showed attenuated behavioral sensitization to a low dose of nicotine (0.05 mg/kg) during repeated daily treatment. (5) NOP receptor knockout mice more rapidly tolerated the sedative effect of nicotine (1 mg/kg), due partially to slightly lower locomotion on first treatment. (6) NOP receptor knockout mice, unlike wild-type mice, showed a significant mecamylamine (2.5 mg/kg) induced conditioned place aversion to nicotine (24 mg/kg/day) withdrawal. These results show that mice lacking the influence of endogenous N/OFQ mice are hypersensitive to nicotine in most measures, showing a role of endogenous nociceptin in modulating or mediating the acute effects of nicotine, and possibly nicotine addiction.     

Modulation of synaptic transmission by nociceptin/orphanin FQ and nocistatin in the spinal cord dorsal horn of mutant mice lacking the nociceptin/orphanin FQ receptor

Nociceptin/orphanin FQ (N/OFQ) and nocistatin (NST) are two neuropeptides derived from the same precursor protein that exhibit opposing effects on spinal neurotransmission and nociception. Here, we have used whole-cell, patch-clamp recordings from visually identified neurons in spinal cord dorsal horn slices of genetically modified mice to investigate the role of the N/OFQ receptor (N/OFQ-R) in the modulatory action of both peptides on excitatory glutamatergic and inhibitory glycinergic and gamma-aminobutyric acid (GABA)-ergic synaptic transmission. In wild-type mice, N/OFQ selectively suppressed excitatory transmission in a concentration-dependent manner but left inhibitory synaptic transmission unaffected. In contrast, NST reduced only inhibitory but not alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor-mediated excitatory synaptic transmission. N/OFQ-mediated inhibition of excitatory transmission was completely absent in N/OFQ-R receptor-deficient (N/OFQ-R(-/-)) mice and significantly reduced in heterozygous (N/OFQ-R(+/-)) mice, whereas the action of NST on inhibitory neurotransmission was completely retained. To test for the relevance of these results for spinal nociception, we investigated the effects of intrathecally injected N/OFQ in the mouse formalin test, an animal model of tonic pain. N/OFQ (3 nmol/mouse) induced significant antinociception in wild-type mice, but had no antinociceptive effects in N/OFQ-R(-/-) mice. These results indicate that the inhibitory action of N/OFQ on excitatory glutamatergic synaptic transmission and its spinal antinociceptive action are mediated via the N/OFQ receptor, whereas the action of NST is independent of this receptor.     

Nonpeptide/peptide chimeric ligands for the nociceptin/orphanin FQ receptor: design,synthesis and in vitro pharmacological activity

Abstract: Nociceptin/orphanin FQ (N/OFQ) is the endogenous ligand for the G‐protein coupled receptor referred to as N/OFQ peptide (NOP) receptor. NOP receptor activation by N/OFQ modulates several biological functions both at central and peripheral level. Structure activity relationship (SAR) studies demonstrated that the N/OFQ sequence can be divided into a N‐terminal tetrapeptide ‘message’ crucial for receptor activation and a C‐terminal ‘address’ important for receptor binding. On the basis of this message/address concept we synthesized some chimeric compounds in which we substituted the natural message domain with the nonselective nonpeptide NOP ligand (8‐Naphthalen‐1‐yl‐methyl‐4‐oxo‐1‐phenyl‐1,3,8‐triaza‐spiro[4,5]dec‐3‐yl)‐aceticacid methyl ester (NNC 63‐0532) and used as address domain the peptide sequences Thr‐NH₂, N/OFQ(5‐9)‐NH₂, N/OFQ(5‐13)‐NH₂ and N/OFQ(5‐17)‐NH₂. All the compounds were pharmacologically evaluated in the electrically stimulated guinea‐pig ileum. NNC 63‐0532 produced a concentration‐dependent inhibition of the electrically induced twitches showing, in comparison with N/OFQ, lower potency and higher maximal effects. In addition, contrary to N/OFQ, the effects of NNC 63‐0532 were insensitive to the NOP selective antagonist [Nphe¹, Arg¹⁴, Lys¹⁵]N/OFQ‐NH₂ (UFP‐101) while prevented by naloxone. Similar results were obtained with NNC 63‐0532/Thr‐NH₂ and NNC 63‐0532/N/OFQ(1‐9)‐NH₂. On the contrary, the inhibitory effects of NNC 63‐0532/N/OFQ(5‐13)‐NH₂ and NNC 63‐0532/N/OFQ(5‐17)‐NH₂ were slightly antagonized by UFP‐101 while naloxone prevented the effects of the high but not of the low concentrations of the two ligands. These data indicate that it is possible to functionalize with the N/OFQ address sequence a nonpeptide NOP ligand for increasing its binding to the NOP receptor. Moreover, these results corroborate the idea that the 5–13 sequence represents the crucial core of the N/OFQ address domain.     

UFP-101, a peptide antagonist selective for the nociceptin/orphanin FQ receptor

Nociceptin/orphanin FQ modulates various biological functions at central and peripheral levels by selectively activating a G-protein coupled receptor named N/OFQ peptide (NOP) receptor. For extending our knowledge on the biological roles of the N/OFQ-NOP receptor system the identification of selective NOP ligands, especially antagonists, is mandatory. [Nphe1, Arg14, Lys15] N/OFQ-NH2 (UFP-101) is a novel NOP ligand that was designed by combining, in the same molecule, the [Nphe1] chemical modification which eliminates efficacy and the [Arg14, Lys15] substitution which increases ligand potency and duration of action in vivo. In the present article, we summarize the pharmacological features of UFP-101 as determined in a series of in vitro and in vivo assays. Moreover, some biological actions and possible therapeutic indications of NOP ligands are discussed on the basis of results obtained with UFP-101. Data obtained with this compound were compared with those generated using other NOP antagonists, especially J-113397 and [Nphe1]N/OFQ(1-13)-NH2, receptor or peptide knockout mice and other pharmacological tools useful for blocking N/OFQ - NOP receptor signaling. The analysis of the available data demonstrates that UFP-101 is a useful pharmacological tool for the investigation of the central and peripheral biological functions regulated by the N/OFQ-NOP receptor system and for defining the therapeutic potential of NOP receptor ligands.     

孤啡肽对创伤大鼠的免疫调节作用

目的:探讨孤啡肽及其受体在创伤大鼠的神经免疫调节作用.方法:采用免疫组织化学,原位杂交,及细胞因子的生物活性检测技术,定量分析内源性孤啡肽及其受体在中枢神经系统的表达及腹腔巨噬细胞分泌IL-1及TNF-α的能力.结果:在正常条件下,孤啡肽及孤啡肽受体mRNA免疫阳性细胞广泛分布于皮层、海马及下丘脑.而在创伤应激作用下,阳性细胞数明显减少.而另一方面,腹腔巨噬细胞分泌IL-1及TNF-α的能力却明显增强.将对照组的~3H掺入值及吸光度定为100％,则在创伤应激作用下,二者的活性分别增强至233％及521％(1:4),195％及566％(1:8),233％及757％(1:16),214％及622％(1:32).侧脑室注射三种剂量的孤啡肽(0.55nmol,0.55nmol,2.75nmol)对IL-1及TNF-α的活性均有显著的下调作用.而且孤啡肽(0.55nmol)的作用能被其受体拮抗剂所阻断.结论:孤啡肽及其受体,作为新的内阿片肽系统,参与创伤应激介导的免疫调节.     

High-affinity, non-peptide agonists for the ORL1 (orphanin FQ/nociceptin) receptor

The discovery of 8-(5,8-dichloro-1,2,3,4-tetrahydro-naphthalen-2-yl)-1-phenyl-1,3,8-triazaspiro[4.5]decan-4-one, 1a, as a high-affinity ligand for the human ORL1 (orphanin FQ/nociceptin) receptor led to the synthesis of a series of optimized ligands. These compounds exhibit high affinity for the human ORL1 receptor, exhibit moderate to good selectivity versus opioid receptors, and behave as full agonists in biochemical assays. In this paper we present the synthesis, structure-activity relationship (SAR), and biochemical characterization of substituted 1-phenyl-1,3,8-triazaspiro[4.5]decan-4-ones culminating in the discovery of 8-(5-methyl-1,2,3,4-tetrahydro-naphthalen-1-yl)-1-phenyl-1,3,8-triazaspiro[4.5]decan-4-one, 1p, and 8-acenaphten-1-yl-1-phenyl-1,3,8-triazaspiro[4.5]decan-4-one 1q, two high-affinity, potent ORL1 receptor agonists with good to moderate selectivity versus the other opioid receptors.     

In vitro characterization of J-113397, a non-peptide nociceptin/orphanin FQ receptor antagonist

The lack of availability of a selective, highly potent, competitive antagonist for the nociceptin receptor (OP4) devoid of residual agonistic activity has hampered studies in this area. We report here the in vitro pharmacological properties of the novel non-peptide OP4 antagonist, J-113397, which was recently discovered by Banyu Pharmaceutical investigators. The compound was synthesized as a racemic mixture in our laboratories. J-113397 was shown to antagonize (pA2 7.52) the nociceptin-induced inhibition of cAMP formation in cells expressing the recombinant human OP4 receptor (CHOhOP4) and to displace [125I]Tyr14nociceptin from CHOhOP4 membranes with a pKi of 8.56. It also competitively antagonized the contractile actions of nociceptin in the mouse colon (pA2 8.07) and the inhibitory effect of nociceptin in electrically stimulated preparations such as the mouse vas deferens (pA2 7.85), the guinea pig ileum (7.75), and the rat vas deferens (7.77). At high concentrations (10 microM), the compound was devoid of agonist activity in the mouse vas deferens and CHOhOP4, while it contracted the mouse colon and increased the twitch response of the rat vas deferens, and produced a naloxone-sensitive inhibition of the electrically evoked twitches in the guinea pig ileum. pA2 values for the new antagonist against deltorphin I in the mouse vas deferens (OP1 receptors), or against dermorphin in the guinea pig ileum (OP3 receptors), etorphine in the rat vas deferens (OP receptors), U69593 in the rabbit vas deferens (OP2 receptors) and endomorphin 1 in the mouse colon (OP3 receptors) were lower than 6. Taken together, these data indicate that J-113397 is a high-affinity, selective and competitive antagonist of the OP4 receptor; this novel pharmacological tool will be of great value in studies directed at evaluating the physiological roles of the nociceptin/OP4 system.     

The molecular and behavioral pharmacology of the orphanin FQ/nociceptin peptide and receptor family

The isolation of an opioid receptor-related clone soon led to the isolation and characterization of a new neuropeptide, termed orphanin FQ or nociceptin (OFQ/N). This heptadecapeptide binds to the NOP(1) (previously termed ORL1) receptor with exceedingly high affinity, but does not interact directly with classical opioid receptors. Functionally, the actions of OFQ/N are diverse and intriguing. Most work has focused upon pain mechanisms, where OFQ/N has potent anti-analgesic actions supraspinally and analgesic actions spinally. Other OFQ/N activities are less clear. The diversity of responses might reflect NOP(1) receptor heterogeneity, but this remains to be established. The actions of this neurochemical system may also be uniquely dependent on contextual factors, both genetic and environmental. This review will address the molecular biology and behavioral pharmacology of OFQ/N and its receptor.     

Involvement of the GABA/benzodiazepine receptor in the axiolytic-like effect of nociceptin/orphanin FQ

We investigated the mechanism underlying the anxiolytic actions of the neuropeptide nociceptin/orphanin FQ (N/OFQ) with an elevated plus-maze test. In mice, intracerebroventricular (i.c.v.) infusions of N/OFQ (0.1 and 0.32 nmol) led to an increase in time spent in the open arms (anxiolytic-like effects). A non-peptidyl N/OFQ receptor (NOP) antagonist, J-113397(1-{(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl}-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one), (1.0 and 3.2 mg/kg, s.c.) blocked the increase induced by N/OFQ. On the other hand, a benzodiazepine receptor antagonist, flumazenil, (10 mg/kg, i.p.) and a GABAA receptor antagonist, (+)-bicuculline, (5.6 mg/kg, i.p.) also inhibited the increase induced by N/OFQ. In rats, microinfusions of N/OFQ (10 and 32 pmol) into the amygdala led to an increase in time spent in the open arms. However, intracranial infusions of N/OFQ (10-100 pmol) into the dorsal hippocampus did not affect the time spent in the open arms. These findings suggest that the anxiolytic-like effects of N/OFQ may be related to the GABA/benzodiazepine system in the amygdala.     

In vitro and in vivo pharmacological characterization of the nociceptin/orphanin FQ receptor ligand Ac-RYYRIK-ol

It was recently reported that the hexapeptide Ac-RYYRIK-ol binds with high affinity nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptors and competitively antagonizes N/OFQ actions in the mouse vas deferens assay. Here we further describe the in vitro and in vivo pharmacological features of this NOP receptor ligand. In mouse brain homogenate the degradation half life of Ac-RYYRIK-ol (2.48 min) was significantly higher than that of the parent compound Ac-RYYRIK-NH2 (1.20 min). In the electrically stimulated mouse vas deferens, Ac-RYYRIK-ol (10-1000 nM) competitively antagonized the inhibitory effect of N/OFQ (pA2=8.46), while in the isolated mouse colon the hexapeptide mimicked N/OFQ contractile effects thus behaving as a NOP receptor agonist (pEC50=9.09). This latter effect was no longer evident in colon tissues taken from mice knock out for the NOP receptor gene (NOP-/-). In vivo in mice, similarly to N/OFQ, Ac-RYYRIK-ol (dose range 0.001-1 nmol) produced: i) pronociceptive effects after intracerebroventricular (i.c.v.) administration and antinociceptive actions when given intrathecally (i.t.) in the tail withdrawal assay; ii) inhibition of locomotor activity and iii) stimulation of food intake after supraspinal administration. Finally, in the forced swimming test, Ac-RYYRIK-ol was inactive per se, but reversed the antidepressant-like effects elicited by the NOP receptor selective antagonist UFP-101 ([Nphe(1),Arg(14),Lys(15)]N/OFQ-NH2). Thus, in all these in vivo assays Ac-RYYRIK-ol mimicked the actions of N/OFQ showing however higher potency. In conclusion, Ac-RYYRIK-ol displayed a complex pharmacological profile which is likely due to the low efficacy agonist nature of this novel ligand of the NOP receptor. The high potency, selectivity of action, and in vivo effectiveness make Ac-RYYRIK-ol a useful pharmacological tool for future studies in the field of N/OFQ and its NOP receptor.     

Effect of nociceptin/orphanin FQ on venous tone in conscious rats

Nociceptin (orphanin FQ) is an endogenous agonist for the opioid receptor-like1 (ORL1) receptor. We investigated the effects of nociceptin on mean circulatory filling pressure, an index of venous tone. The effects of nociceptin (10, 30 nmol/kg, i.v.) and the vehicle (0.9% NaCl) on mean arterial pressure, heart rate and mean circulatory filling pressure were examined in two groups each of conscious rats: rats with, or without, ganglionic blockade through pretreatment with mecamylamine (1 mg/kg, i.v.) and noradrenaline (2 microg/kg min, i.v.). In the unblocked rats, both doses of nociceptin decreased mean arterial pressure and heart rate, and the high dose also decreased mean circulatory filling pressure. In the ganglionic-blocked rats, nociceptin did not alter heart rate but caused greater reductions of mean arterial pressure and mean circulatory filling pressure. The vehicle had no effects in any group. Therefore, nociceptin is a depressor agent with prominent direct venodilator and bradycardic action.     

Effects of adinazolam on plasma catecholamine, heart rate and blood pressure responses in stressed and non-stressed rats.

Adinazolam (ADI) is a new benzodiazepine with anxiolytic and antidepressant properties. To assess its effects on the acute stress response, rats were given a single intraperitoneal injection of 2.5 or 5.0 mg/kg of ADI and stressed for 1 hr by restraint. Neither dose of ADI had any effect on heart rate, blood pressure or norepinephrine (NE) and epinephrine (EP) in plasma in the resting rats. In the stressed animal, 2.5 and 5.0 mg/kg of ADI did not affect stress-induced increases in heart rate or blood pressure but both significantly reduced the stress-induced increases in plasma NE and EP. During certain stressful experiences in patients with abnormally-increased sympathetic drive, ADI may be therapeutically useful in reducing high levels of catecholamines.     

Effects of maternal separation on brain nociceptin/orphanin FQ peptide levels in male Wistar rats

Environmental manipulation early in life may induce persistent alterations in adult behaviour and physiology. In this study, we investigated the long-term effects of daily maternal separation, Days 1-21, on brain immunoreactive nociceptin/orphanin FQ (ir-N/OFQ) levels in male Wistar rats. The rat pups were separated in litters for 360 min (MS360) or 15 min (H15). Control rats were left undisturbed until weaning. Peptide levels were measured at 10 weeks of age. In the hypothalamus and periaqueductal gray, MS360 induced an increase in ir-N/OFQ levels in comparison with control rats. H15 rats had increased ir-N/OFQ levels in the hypothalamus and the medial prefrontal cortex compared with control animals. The rats were also tested at two occasions in an elevated plus-maze. An increased anxiety-like behaviour was shown in MS360 rats at weaning, whereas a decreased anxiety response was found at 9 weeks of age compared with control rats. The study shows that early life experiences induce long-term effects on behaviour, as well as brain N/OFQ levels.     

Effect of nociceptin/orphanin FQ on the rewarding properties of morphine

The present study investigated the effect of nociceptin/orphanin FQ, the endogenous ligand of the opioid receptor-like 1 (ORL1) receptor, on the rewarding properties of morphine in the place conditioning paradigm. Intracerebroventricular (i.c.v.) injections of nociceptin/orphanin FQ, 500 or 1000 (but not 250) ng/rat, abolished conditioned place preference induced by subcutaneous (s.c.) injections of morphine (3 mg/kg). These doses of nociceptin/orphanin FQ induced neither place aversion nor preference per se. The same doses did not modify the rat performance in the Morris water test, suggesting that they do not disrupt spatial learning and memory. Moreover, these doses of nociceptin/orphanin FQ did not modify the development of morphine-induced locomotor sensitization, suggesting that they do not interfere with sensitization processes to morphine. The present results confirm and extend previous reports that nociceptin/orphanin FQ is able to abolish morphine-induced conditioned place preference, and raise interest for the possible role of nociceptin/orphanin FQ and ORL1 receptors in the control of opiate abuse.