Participação da neurotransmissão dopaminergica no efeito hiperlocomotor do neuropeptideo S

Neuropeptide S (NPS) is an endogenous 20-aminoacid peptide which binds a G protein-coupled receptor named NPSR. This peptidergic system is involved in the modulation of several biological functions, such as locomotion, anxiety, nociception, food intake and motivational behaviors. Studies have shown the participation of NPSR receptors in mediating the hyperlocomotor effects of NPS. A growing body of evidence suggests the participation of adenosinergic, dopaminergic and CRF systems on the hyperlocomotor effects of NPS. Considering that little is known about the role of dopaminergic system in mediating NPS-induced hyperlocomotion, the present study aims to investigate the locomotor actions of intracerebroventricular (icv) NPS in mice pretreated with α-metil-p-tirosine (AMPT, inhibitor of dopamine synthesis), reserpine (inhibitor of dopamine vesicle storage) or sulpiride (D2 receptor antagonist) in the open field test. A distinct group of animals received the same pretreatments described above (AMPT, reserpine or sulpiride) and the hyperlocomotor effects of methylphenidate (dopamine reuptake inhibitor) were investigated in the open field. NPS and methylphenidate increased the mouse locomotor activity. AMPT per se did not change the locomotion of the animals, but it partially reduced the hyperlocomotion of methylphenidate. The pretreatment with AMPT did not affect the psychostimulant effects of NPS. Both reserpine and sulpiride inhibited the stimulatory actions of NPS and methylphenidate. These findings show that the hyperlocomotor effects of methylphenidate, but not NPS, were affected by the pretreatment with AMPT. Furthermore, methylphenidate- and NPS-induced hyperlocomotion was impaired by reserpine and sulpiride pretreatments. Together, data suggests that NPS can increase locomotion even when the synthesis of catecholamines was impaired. Additionally, the hyperlocomotor effects of NPS and methylphenidate depend on monoamines vesicular storaged, mainly dopamine, and on the activation of D2 receptors. The psychostimulant effects of NPS via activation of dopaminergic system display clinical significance on the treatment of diseases which involves dopaminergic pathways, such as Parkinson s disease and drug addiction

Efeito de ligantes do receptor NOP no modelo animal de mania induzido por metilfenidato

Bipolar disorder is a chronic psychopathology that reaches from 1 to 4% of the world population. This mood disorder is characterized by cyclical mood changes, in which an individual alternates between states of depression and mania. Mania is described in the literature as an abnormal state of exacerbation of humor, in which the subject presents an expansive, euphoric behavior, but with increased irritability, psychomotor agitation and a feeling of invincibility, which will contribute to risks exposure. The treatment of this psychopathology is complex and it is not effective in all cases, and it evokes many side effects. In this respect, the system of Nociceptin/Orphanin FQ (N/OFQ) can be studied as a possible therapeutic target for the treatment of bipolar disorder, due to its modulatory role on monoaminergic systems and on mood. This study aims to investigate the effect of NOP receptor ligands in an animal model of mania induced by methylphenidate. To this aim, locomotor activity was assessed in an open field, in mice treated with methylphenidate (10 mg/kg, sc, 15 min). Valproate (300 mg / kg, ip, 30 min), standard treatment of mania, prevented methylphenidate-induced hyperlocomotion. The acute treatment with the antagonist of NOP receptor UFP-101 (1-10 nmol, icv, 5 min) per se did not affect the spontaneous locomotion of mice, but it was able of attenuating hyperlocomotion induced by methylphenidate. The acute treatment with N/OFQ (1 and 0.1 nmol, icv, 5 min) did not alter the distance moved, but when tested at a dose of 1 ηmol, N/OFQ slightly reduced methylphenidate-induced hiperlocomotion. In conclusion, the administration of UFP-101 and N/OFQ produced antimanic-like actions. Furthermore, these data suggest that the system of N/OFQ performs a complex modulation of voluntary movement, and consequently on dopaminergic neurotransmission.

Padronização de testes para avaliação do estado de mania e potencial anti-maníaco de um agonista do receptor NOP

Bipolar disorder is characterized by mood impairment, alternating between mania/hypomania and depression, and its exact pathophysiology is already unknown. The treatment of bipolar disorder is based on prevention of the manic and depressive episodes using mood stabilizers. Nociceptin/orfanin FQ (N/OFQ) is an endogenous heptadecapeptide which binds as an agonist to NOP receptor, which is a G-coupled inhibitory receptor. N/OFQ and its receptor modulate a lot of functions in the organism, including emotional processes. It is known that the plasmatic concentration of N/OFQ is altered in patients in both phases depressive and manic of bipolar disorder and it is assumed that this system has a role on the etiology of this disorder. Concerning mania, the animal models used in research tend to focus in an unique aspect of the manic behavior, as hyperactivity or agressivity. In the 60’s, the hole board test was proposed, and it consists of an apparatus with holes where a behavior known as head-dippings is measured. High levels of head-dippings are suggestive of neophilia, while low levels can be characteristic of an anxious-like behavior. As the increase of exploratory and goal-directed behavior are characteristics of manic behavior, this test could help in mania research. Thus, this work was organized in 3 steps and aims to: (1) investigate the induction of a manic-like state promoted by ouabain, a Na+/K+-ATPase inhibitor, in the mouse open field test; (2) set up the hole board as a test to measure manic-like behaviors; and (3) investigate the N/OFQ effects in prevention of this kind of behavior on hole board. Male Swiss mice were used in this study, and they take part of only one of the described steps. Depending on the step performed, mice received one or more of the following treatments: (1) ouabain 10-6 , 10-5 , 10-4 , 10-3 or 10-2 M, intracerebroventricular (icv); (2) sodium valproate 300 mg/kg, intraperitoneal (ip); (3) sodium valproate 400 mg/kg, ip; (4) diazepam 1 mg/kg, ip; (5) methylphenidate 10 mg/kg, ip; and (6) N/OFQ 0,1 or 1 nmol, icv. The results suggest that hole board can be used to evaluate a manic state, through analysis of different animal behaviors. However, it was not possible to standard the model of Na+ /K+ -ATPase dysfunction through ouabain administration in mice. Moreover, the data suggest that N/OFQ, at the doses tested, has not affected the methylphenidate-induced mania-like behavior. Taken together, the results point to a new approach of manic research, through the hole board using. However, more studies are necessary in order to verify the role of N/OFQ system on bipolar disorder.

Efeitos in vivo e in vitro de agonistas parciais do receptor NOP: implicações para o tratamento da ansiedade, depressão e mania

Introduction: This study aimed to investigate the effects of the two peptide NOP partial agonists (UFP-113 and [F/G]N/OFQ(1-13)NH2) and the non peptide NOP partial agonist (AT-090) in the mouse emotional behavior as well as in the intracellular transduction pathways following the receptor binding. Methods: Male Swiss or CD-1 mice were used in this study together with NOP(+/+) and NOP(-/-) mice. The elevated plus maze (EPM) was used to evaluate the effects of compounds on anxiety-like behaviors. Diazepam and the NOP agonists, N/OFQ and Ro 65-6570, were used as positive controls in the EPM. NOP(+/+) and NOP(-/-) mice were used to evaluate the selectivity of those compounds that induced anxiolytic-like behaviors. The forced swim test (FST) was used to evaluate the effects of compounds on depressive-like behaviors. Nortriptyline and the NOP antagonists, UFP-101 and SB-612111, were used as positive controls in the FST. The effects of N/OFQ, UFP-101, SB-612111, UFP-113, [F/G]N/OFQ(1-13)NH2, and AT-090 were assessed in the methylphenidate-induced hyperlocomotion (MIH) test; in this assay valproate was used as positive control. The G protein and β-arrestin 2 transduction pathways of NOP receptor agonists (N/OFQ and Ro 65-6570), antagonist (UFP-101), and partial agonists (UFP-113, [F/G]N/OFQ(1-13)NH2, and AT-090) were also evaluated using an innovative assay that measures a bioluminescence resonance energy transfer process. For this, cell lines permanently co-expressing the NOP receptor coupled to luciferase (energy donor), and green fluorescent protein (energy acceptor) coupled to one of the effector proteins (G protein or β-arrestin 2) were used. Results: Diazepam (1 mg/kg), N/OFQ (1 nmol), Ro 65-6570 (0.1 mg/kg), and AT-090 (0.01 mg/kg) induced anxiolytic-like effect in mice in the EPM. The effects of Ro 65-6570 and AT-090 were selective to NOP receptor. UFP-113 (0.01-1 nmol) and [F/G]N/OFQ(1-13)NH2 (0.1-3 nmol) were inactive in the EPM. In the FST, nortriptyline (30 mg/kg), UFP-101 (10 nmol), SB-612111 (10 mg/kg), UFP-113 (0.01 and 0.1 nmol), and [F/G]N/OFQ(1-13)NH2 (0.3 and 1 nmol) induced antidepressant-like effects, while AT-090 (0.001-0.1 mg/kg) was inactive in this assay. The effects of UFP-113 and [F/G]N/OFQ(1-13)NH2 were selective to NOP receptor. Valproate (400 mg/kg) counteracted methylphenidate (MPH, 10 mg/kg)-induced hyperlocomotion in mice in the open field. N/OFQ (1 nmol), UFP-113 (0.01-0.1 nmol), and [F/G]N/OFQ(1-13)NH2 (1 nmol) were also able to reduce the MPH-induced hyperlocomotion, without changing the locomotor activity per se. The effect of UFP-113 was selective to NOP receptor. The UFP-101 (10 nmol), SB-612111 (10 mg/kg), and AT-090 (0.001-0.03 mg/kg) did not change the hyperlocomotor effect of methylphenidate. In vitro, N/OFQ and Ro 65-6570 behaved as NOP full agonists for G-protein and β-arrestin 2 pathways. AT-090 behaved as NOP receptor partial agonist for both transduction pathways, while UFP-113 and [F/G]N/OFQ(1-13)NH2 behaved as partial agonists and antagonists of NOP receptor for NOP/G protein and NOP/β-arrestin 2, respectively. UFP-101 behaved as NOP receptor antagonist for both transduction pathways. Conclusion: NOP ligands producing same effects on NOP/G protein interaction (partial agonism), but with opposite effects on β-arrestin 2 recruitment (partial agonism vs antagonism), can promote different in vivo effects on anxiety and mood as it was observed in the behavioral tests. This work corroborates the potential of NOP receptor as an innovative pharmacological target for the treatment of emotional disorders.

Efeitos in vivo e in vitro de agonistas parciais do receptor NOP: implicações para o tratamento da ansiedade, depressão e mania

Introduction: This study aimed to investigate the effects of the two peptide NOP partial agonists (UFP-113 and [F/G]N/OFQ(1-13)NH2) and the non peptide NOP partial agonist (AT-090) in the mouse emotional behavior as well as in the intracellular transduction pathways following the receptor binding. Methods: Male Swiss or CD-1 mice were used in this study together with NOP(+/+) and NOP(-/-) mice. The elevated plus maze (EPM) was used to evaluate the effects of compounds on anxiety-like behaviors. Diazepam and the NOP agonists, N/OFQ and Ro 65-6570, were used as positive controls in the EPM. NOP(+/+) and NOP(-/-) mice were used to evaluate the selectivity of those compounds that induced anxiolytic-like behaviors. The forced swim test (FST) was used to evaluate the effects of compounds on depressive-like behaviors. Nortriptyline and the NOP antagonists, UFP-101 and SB-612111, were used as positive controls in the FST. The effects of N/OFQ, UFP-101, SB-612111, UFP-113, [F/G]N/OFQ(1-13)NH2, and AT-090 were assessed in the methylphenidate-induced hyperlocomotion (MIH) test; in this assay valproate was used as positive control. The G protein and β-arrestin 2 transduction pathways of NOP receptor agonists (N/OFQ and Ro 65-6570), antagonist (UFP-101), and partial agonists (UFP-113, [F/G]N/OFQ(1-13)NH2, and AT-090) were also evaluated using an innovative assay that measures a bioluminescence resonance energy transfer process. For this, cell lines permanently co-expressing the NOP receptor coupled to luciferase (energy donor), and green fluorescent protein (energy acceptor) coupled to one of the effector proteins (G protein or β-arrestin 2) were used. Results: Diazepam (1 mg/kg), N/OFQ (1 nmol), Ro 65-6570 (0.1 mg/kg), and AT-090 (0.01 mg/kg) induced anxiolytic-like effect in mice in the EPM. The effects of Ro 65-6570 and AT-090 were selective to NOP receptor. UFP-113 (0.01-1 nmol) and [F/G]N/OFQ(1-13)NH2 (0.1-3 nmol) were inactive in the EPM. In the FST, nortriptyline (30 mg/kg), UFP-101 (10 nmol), SB-612111 (10 mg/kg), UFP-113 (0.01 and 0.1 nmol), and [F/G]N/OFQ(1-13)NH2 (0.3 and 1 nmol) induced antidepressant-like effects, while AT-090 (0.001-0.1 mg/kg) was inactive in this assay. The effects of UFP-113 and [F/G]N/OFQ(1-13)NH2 were selective to NOP receptor. Valproate (400 mg/kg) counteracted methylphenidate (MPH, 10 mg/kg)-induced hyperlocomotion in mice in the open field. N/OFQ (1 nmol), UFP-113 (0.01-0.1 nmol), and [F/G]N/OFQ(1-13)NH2 (1 nmol) were also able to reduce the MPH-induced hyperlocomotion, without changing the locomotor activity per se. The effect of UFP-113 was selective to NOP receptor. The UFP-101 (10 nmol), SB-612111 (10 mg/kg), and AT-090 (0.001-0.03 mg/kg) did not change the hyperlocomotor effect of methylphenidate. In vitro, N/OFQ and Ro 65-6570 behaved as NOP full agonists for G-protein and β-arrestin 2 pathways. AT-090 behaved as NOP receptor partial agonist for both transduction pathways, while UFP-113 and [F/G]N/OFQ(1-13)NH2 behaved as partial agonists and antagonists of NOP receptor for NOP/G protein and NOP/β-arrestin 2, respectively. UFP-101 behaved as NOP receptor antagonist for both transduction pathways. Conclusion: NOP ligands producing same effects on NOP/G protein interaction (partial agonism), but with opposite effects on β-arrestin 2 recruitment (partial agonism vs antagonism), can promote different in vivo effects on anxiety and mood as it was observed in the behavioral tests. This work corroborates the potential of NOP receptor as an innovative pharmacological target for the treatment of emotional disorders.