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Acuña LR, Back F, Barp CG, Guilherme Tassoni Bortoloci J, Assreuy J, Carobrez AP. Role of nitric oxide on defensive behavior and long-term aversive learning induced by chemical stimulation of the dorsolateral periaqueductal gray matter. Neurobiol Learn Mem 2023; 200:107735. [PMID: 36813080 DOI: 10.1016/j.nlm.2023.107735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 11/23/2022] [Accepted: 02/16/2023] [Indexed: 02/23/2023]
Abstract
The midbrain periaqueductal gray matter, especially the dorsolateral portion (dlPAG), coordinates immediate defensive responses (DR) to threats, but also ascends forebrain information for aversive learning. The synaptic dynamics in the dlPAG regulate the intensity and type of behavioral expression, as well as long-term processes such as memory acquisition, consolidation, and retrieval. Among several neurotransmitters and neural modulators, nitric oxide seems to play an important regulatory role in the immediate expression of DR, but it remains unclear if this gaseous on-demand neuromodulator contributes to aversive learning. Therefore, the role of nitric oxide in the dlPAG was investigated, during conditioning in an olfactory aversive task. The behavioral analysis consisted of freezing and crouch-sniffing in the conditioning day after glutamatergic NMDA agonist injection into the dlPAG. Two days later, rats were re-exposed to the odor cue and avoidance was measured. 7NI, a selective neuronal nitric oxide synthase inhibitor (40 and 100 nmol), injected before NMDA (50 pmol) impaired immediate DR and consequent aversive learning. The scavenging of extrasynaptic nitric oxide by C-PTIO (1 and 2 nmol) induced similar results. Moreover, spermine NONOate, a nitric oxide donor (5, 10, 20, 40, and 80 nmol), produced DR by itself, but only the low dose also promoted learning. The following experiments utilized a fluorescent probe, DAF-FM diacetate (5 µM), directly into the dlPAG, to quantify nitric oxide in the three previous experimental situations. Nitric oxide levels were increased after NMDA stimulation, decreased after 7NI, and increased after spermine NONOate, in line with alterations in defensive expression. Altogether, the results indicate that nitric oxide plays a modulatory and decisive role in the dlPAG regarding immediate DR and aversive learning.
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Affiliation(s)
- Lucía R Acuña
- Department of Pharmacology, Universidade Federal de Santa Catarina, Brazil; Instituto Misionero de Biodiversidad, Puerto Iguazú, Argentina
| | - Franklin Back
- Department of Pharmacology, Universidade Federal de Santa Catarina, Brazil
| | - Clarissa G Barp
- Department of Pharmacology, Universidade Federal de Santa Catarina, Brazil
| | | | - Jamil Assreuy
- Department of Pharmacology, Universidade Federal de Santa Catarina, Brazil
| | - Antonio P Carobrez
- Department of Pharmacology, Universidade Federal de Santa Catarina, Brazil.
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2
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Brianis RC, Lima RC, Moreira FA, Aguiar DC. Anti-aversive effect of 2-arachidonoylglycerol in the dorsolateral periaqueductal gray of male rats in contextual fear conditioning and Vogel tests. Behav Pharmacol 2022; 33:213-221. [PMID: 34074811 DOI: 10.1097/fbp.0000000000000639] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The endocannabinoid system modulates the stress coping strategies in the dorsolateral periaqueductal grey (dlPAG). The most relevant endocannabinoids, anandamide and 2-arachidonoylglycerol (2-AG) exert inhibitory control over defensive reactions mediated by the dlPAG. However, the protective role of anandamide is limited by its lack of effect in higher concentrations. Thus, the 2-AG emerges as a complementary target for developing new anxiolytic compounds. Nevertheless, the role of 2-AG on stress responsivity may vary according to the nature of the stimulus. In this study, we verified whether the dlPAG injection of 2-AG or inhibitors of its hydrolysis induce anxiolytic-like effects in male Wistar rats exposed to behavioral models in which physical stress (mild electric shock) is a critical component, namely the contextual fear conditioning test (CFC) and the Vogel conflict test (VCT). We also investigated the contribution of cannabinoid receptor type 1 (CB1) and type 2 (CB2) in such effects. The facilitation of 2-AG signaling in the dlPAG reduced contextual fear expression and exhibited an anxiolytic-like effect in the VCT in a mechanism dependent on activation of CB1 and CB2. However, the VCT required a higher dose than CFC. Further, the monoacylglycerol inhibitors, which inhibit the hydrolysis of 2-AG, were effective only in the CFC. In conclusion, we confirmed the anti-aversive properties of 2-AG in the dlPAG through CB1 and CB2 mechanisms. However, these effects could vary according to the type of stressor and the anxiety model employed.
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Affiliation(s)
- Rayssa C Brianis
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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3
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Lopes LT, Canto-de-Souza L, Baptista-de-Souza D, de Souza RR, Nunes-de-Souza RL, Canto-de-Souza A. The interplay between 5-HT 2C and 5-HT 3A receptors in the dorsal periaqueductal gray mediates anxiety-like behavior in mice. Behav Brain Res 2022; 417:113588. [PMID: 34547341 DOI: 10.1016/j.bbr.2021.113588] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 08/17/2021] [Accepted: 09/15/2021] [Indexed: 11/17/2022]
Abstract
The monoamine neurotransmitter serotonin (5-HT) modulates anxiety by its activity on 5-HT2C receptors (5-HT2CR) expressed in the dorsal periaqueductal gray (dPAG). Here, we investigated the presence of 5-HT3A receptors (5-HT3AR) in the dPAG, and the interplay between 5-HT2CR and 5-HT3AR in the dPAG in mediating anxiety-like behavior in mice. We found that 5-HT3AR is expressed in the dPAG and the blockade of these receptors using intra-dPAG infusion of ondansetron (5-HT3AR antagonist; 3.0 nmol) induced an anxiogenic-like effect. The activation of 5-HT3ABR by the infusion of mCPBG [1-(m-Chlorophenyl)-biguanide; 5-HT3R agonist] did not alter anxiety-like behaviors. In addition, blockade of 5-HT3AR (1.0 nmol) prevented the anxiolytic-like effect induced by the infusion of the 5-HT2CR agonist mCPP (1-(3-chlorophenyl) piperazine; 0.03 nmol). None of the treatment effects on anxiety-like behaviors altered the locomotor activity levels. The present results suggest that the anxiolytic-like effect exerted by serotonin activity on 5-HT2CR in the dPAG is modulated by 5-HT3AR expressed in same region.
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Affiliation(s)
- Luana Tenorio Lopes
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, The University of Calgary, Calgary, Alberta, Canada.
| | - Lucas Canto-de-Souza
- Laboratory of Pharmacology, School of Pharmaceutical Sciences, Univ. Estadual Paulista, UNESP, Araraquara, SP 14801-902, Brazil; Neuroscience and Behavioral Institute, Av. do Café, 2.450, 14050-220 Ribeirão Preto, SP, Brazil.
| | - Daniela Baptista-de-Souza
- Psychobiology Group/Department of Psychology/CECH-UFSCar, São Carlos, SP 13565-905, Brazil; Laboratory of Pharmacology, School of Pharmaceutical Sciences, Univ. Estadual Paulista, UNESP, Araraquara, SP 14801-902, Brazil; Neuroscience and Behavioral Institute, Av. do Café, 2.450, 14050-220 Ribeirão Preto, SP, Brazil.
| | - Rimenez Rodrigues de Souza
- The University of Texas at Dallas, School of Behavior and Brain Sciences, 800 West Campbell Road, Richardson, TX 75080-3021, United States; The University of Texas at Dallas, Texas Biomedical Device Center, 800 West Campbell Road, Richardson, TX 75080-3021, United States.
| | - Ricardo L Nunes-de-Souza
- Psychobiology Group/Department of Psychology/CECH-UFSCar, São Carlos, SP 13565-905, Brazil; Joint Graduate Program in Physiological Sciences UFSCar/UNESP, Rod. Washington Luís, Km 235, São Carlos, SP 13565-905, Brazil; Laboratory of Pharmacology, School of Pharmaceutical Sciences, Univ. Estadual Paulista, UNESP, Araraquara, SP 14801-902, Brazil; Neuroscience and Behavioral Institute, Av. do Café, 2.450, 14050-220 Ribeirão Preto, SP, Brazil.
| | - Azair Canto-de-Souza
- Psychobiology Group/Department of Psychology/CECH-UFSCar, São Carlos, SP 13565-905, Brazil; Joint Graduate Program in Physiological Sciences UFSCar/UNESP, Rod. Washington Luís, Km 235, São Carlos, SP 13565-905, Brazil; Graduate Program in Psychology UFSCar, Rod. Washington Luís, Km 235, São Carlos, SP 13565-905, Brazil; Neuroscience and Behavioral Institute, Av. do Café, 2.450, 14050-220 Ribeirão Preto, SP, Brazil.
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4
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Fernandes GG, Frias AT, Spiacci A, Pinheiro LC, Tanus-Santos JE, Zangrossi H. Nitric oxide in the dorsal periaqueductal gray mediates the panic-like escape response evoked by exposure to hypoxia. Prog Neuropsychopharmacol Biol Psychiatry 2019; 92:321-327. [PMID: 30742862 DOI: 10.1016/j.pnpbp.2019.02.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 02/04/2019] [Accepted: 02/07/2019] [Indexed: 02/02/2023]
Abstract
Exposure of rats to an environment with low O2 levels evokes a panic-like escape behavior and recruits the dorsal periaqueductal gray (dPAG), which is considered to be a key region in the pathophysiology of panic disorder. The neurochemical basis of this response is, however, currently unknown. We here investigated the role played by nitric oxide (NO) within the dPAG in mediation of the escape reaction induced by hypoxia exposure. The results showed that exposure of male Wistar rats to 7% O2 increased nitrite levels, a NO metabolite, in the dPAG but not in the amygdala or hypothalamus. Nitrite levels in the dPAG were correlated with the number of escape attempts during the hypoxia challenge. Injections of the NO synthesis inhibitor NPA, the NO-scavenger c- PTIO, or the NMDA receptor antagonist AP-7 into the dorsolateral column of the periaqueductal gray (dlPAG) inhibited escape expression during hypoxia, without affecting the rats' locomotion. Intra-dlPAG administration of c-PTIO had no effect on the escape response evoked by the elevated-T maze, a defensive behavior that has also been associated with panic attacks. Altogether, our results suggest that NO plays a critical role in mediation of the panic-like defensive response evoked by exposure to low O2 concentrations.
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Affiliation(s)
- Gabriel Gripp Fernandes
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil
| | - Alana Tercino Frias
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil
| | - Ailton Spiacci
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil
| | - Lucas C Pinheiro
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil
| | | | - Hélio Zangrossi
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
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Batista LA, Moreira FA. Cannabinoid CB 1 receptors mediate the anxiolytic effects induced by systemic alprazolam and intra-periaqueductal gray 5-HT 1A receptor activation. Neurosci Lett 2019; 703:5-10. [PMID: 30858018 DOI: 10.1016/j.neulet.2019.03.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 03/01/2019] [Accepted: 03/07/2019] [Indexed: 01/04/2023]
Abstract
The endocannabinoid system has been implicated in the modulation of behaviors related to anxiety and panic disorders. Accordingly, facilitation of CB1 receptor signaling reduces the consequences of aversive stimuli in animal models. However, the role of the CB1 receptor in the effects of anxiolytic drugs has remained unclear. Here, we tested the hypothesis that the anxiolytic and panicolytic responses to systemic alprazolam injection and local 5-HT1A receptor activation in the dorsolateral periaqueductal gray (dlPAG) depend on CB1 receptor activation. Systemic injection of alprazolam (4 mg/kg) induced an anxiolytic-like effect in the elevated T maze (ETM) model of panic and anxiety, which was prevented by the CB1 antagonist AM251 (0.3 mg/kg). Likewise, intra-dlPAG injection of the 5-HT1A receptor agonist 8-OH-DPAT (3.2 nmol/0.2 u L) also reduced anxiety-like behavior, a response prevented by intra-dlPAG injection of AM251 (100 pmol/0.2 µL). 8-OH-DPAT (8 nmol/0.2 µL) also presented a panicolytic-like activity in the escape reaction induced by chemical stimulation of the dlPAG, which was not prevented by AM251 (100 pmol/0.2 µL). These results suggest that CB1 receptor signaling is involved in the effects of anxiolytic drugs, with potential implications for developing new treatments for anxiety disorders.
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Affiliation(s)
- Luara A Batista
- Graduate School in Neuroscience, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Brazil.
| | - Fabricio A Moreira
- Graduate School in Neuroscience, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Brazil; Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Brazil
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6
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Faria MP, Miguel TT, Gomes KS, Nunes-de-Souza RL. Anxiety-like responses induced by nitric oxide within the BNST in mice: Role of CRF1 and NMDA receptors. Horm Behav 2016; 79:74-83. [PMID: 26774463 DOI: 10.1016/j.yhbeh.2016.01.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2015] [Revised: 12/10/2015] [Accepted: 01/11/2016] [Indexed: 11/28/2022]
Abstract
It has been shown that the bed nucleus of the stria terminalis (BNST) of rats contains nitrergic neurons, which are activated during animal exposure to aversive stimuli. The BNST is also populated by glutamatergic and corticotrophin releasing factor (CRFergic) neurons, which in turn are activated under stressful situations. Here we investigated the anxiogenic-like effects of intra-BNST injections of a nitric oxide (NO) donor, NOC-9 in mice. The role of CRFergic and glutamatergic systems on defensive behavior induced by NOC-9 was investigated with previous intra-BNST infusion of different doses of CP376395, a CRF type 1 receptor antagonist (CRF1), or AP-7, an NMDA (N-methyl-D-aspartate) receptor antagonist. Anxiety-like behavior was assessed immediately and 5 min after intra-BNST drug injection, exposing mice to a novel arena and to the elevated plus-maze (EPM; an anxiogenic situation). Results showed that NOC-9 provoked a short period (≈ 150 s) of freezing behavior in the novel arena and increased anxiety in the EPM. Both CP and AP-7 attenuated the anxiogenic-like effects of NOC-9 in the EPM without changing freezing behavior in the novel arena. When given alone (i.e. without prior intra-BNST injection of NOC-9), AP-7 (0.20 nmol), but not CP (0.75, 1.50, or 3.00 nmol), attenuated anxiety in mice exposed to the EPM. These results suggest that CRF1 and NMDA receptors located within the BNST differentially modulate aversive effects induced by NO production in this limbic forebrain structure.
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MESH Headings
- Aminopyridines/pharmacology
- Animals
- Anxiety/chemically induced
- Anxiety/metabolism
- Behavior, Animal/drug effects
- Corticotropin-Releasing Hormone/metabolism
- Freezing Reaction, Cataleptic/drug effects
- Male
- Maze Learning/drug effects
- Mice
- Neurons/drug effects
- Neurons/metabolism
- Neurons/pathology
- Nitric Oxide/pharmacology
- Receptors, Corticotropin-Releasing Hormone/antagonists & inhibitors
- Receptors, Corticotropin-Releasing Hormone/metabolism
- Receptors, Corticotropin-Releasing Hormone/physiology
- Receptors, N-Methyl-D-Aspartate/metabolism
- Receptors, N-Methyl-D-Aspartate/physiology
- Septal Nuclei/drug effects
- Stress, Psychological/chemically induced
- Stress, Psychological/metabolism
- Stress, Psychological/psychology
- Triazenes/pharmacology
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Affiliation(s)
- M P Faria
- Programa Interinstitucional de Pós-Graduação em Ciências Fisiológicas, Universidade Federal de São Carlos and Universidade Estadual Paulista, Araraquara, SP, Brazil; Laboratório de Farmacologia, Faculdade de Ciências Farmacêuticas, Universidade Estadual Paulista, 14800-903 Araraquara, SP, Brazil
| | - T T Miguel
- Farmacologia, Universidade Federal de Uberlândia, Uberlândia, MG, Brazil
| | - K S Gomes
- Laboratório de Farmacologia, Faculdade de Ciências Farmacêuticas, Universidade Estadual Paulista, 14800-903 Araraquara, SP, Brazil
| | - R L Nunes-de-Souza
- Programa Interinstitucional de Pós-Graduação em Ciências Fisiológicas, Universidade Federal de São Carlos and Universidade Estadual Paulista, Araraquara, SP, Brazil; Laboratório de Farmacologia, Faculdade de Ciências Farmacêuticas, Universidade Estadual Paulista, 14800-903 Araraquara, SP, Brazil.
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7
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Vila-Verde C, Marinho ALZ, Lisboa SF, Guimarães FS. Nitric oxide in the prelimbic medial prefrontal cortex is involved in the anxiogenic-like effect induced by acute restraint stress in rats. Neuroscience 2016; 320:30-42. [PMID: 26812037 DOI: 10.1016/j.neuroscience.2016.01.040] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 01/02/2016] [Accepted: 01/18/2016] [Indexed: 12/13/2022]
Abstract
Neurons containing the neuronal nitric oxide synthase (nNOS) enzyme are located in brain areas related to defensive behavior, such as the ventromedial prefrontal cortex (vMPFC). Rats exposed to a live predator (a cat) present anxiety-like behavior and an increased number of nNOS-positive neurons in this brain area one-week later. Moreover, stress-related behavioral changes in rodents can be prevented by systemic or local vMPFC nNOS inhibition. In the present study we investigated if acute restraint stress (RS)-induced delayed (one-week) anxiogenic-like effect was associated with increased nNOS expression or activity in the vMPFC. Furthermore, we also tested if local pharmacological nNOS inhibition would prevent stress-induced behavioral changes. Male Wistar rats were submitted to RS for 3h and tested in the elevated plus maze (EPM) 24h or 7 days later. Two hours after the EPM test, their brains were removed, processed and nNOS expression in the vMPFC was evaluated by immunohistochemistry. Another group of animals was used for measuring NO metabolites (NOx; an indirect measure of NOS activity) immediately after the EPM test, 24h after RS. Independent groups had guide cannula implanted bilaterally into the prelimbic (PL) portion of vMPFC. Five to six days after surgery, the animals were submitted to RS and 24h later received local administration of the nNOS inhibitor, N-propyl-l-arginine (NPLA; 0.04 nmol). They were tested in the EPM 10 min later. RS-induced anxiogenic-like effect was accompanied by increased nNOS expression in the PL (p<0.05), but not in the infralimbic (IL) vMPFC, both 24h and 7 days after RS. Moreover, open-arm exploration of the EPM was negatively correlated with nNOS expression (p<0.05) and NOx levels (p<0.05) in the PL. The anxiogenic-like effect observed 24h after RS was prevented by NPLA (p<0.05). Our results suggest that RS-induced anxiogenic-like effect might depend on increased nNOS-mediated signaling in the PL MPFC.
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Affiliation(s)
- C Vila-Verde
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of São Paulo, Brazil.
| | - A L Z Marinho
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of São Paulo, Brazil
| | - S F Lisboa
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of São Paulo, Brazil.
| | - F S Guimarães
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of São Paulo, Brazil
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Gobira PH, Almeida-Santos AF, Guimaraes FS, Moreira FA, Aguiar DC. Role of the endocannabinoid 2-arachidonoylglycerol in aversive responses mediated by the dorsolateral periaqueductal grey. Eur Neuropsychopharmacol 2016; 26:15-22. [PMID: 26628106 DOI: 10.1016/j.euroneuro.2015.11.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Revised: 09/14/2015] [Accepted: 11/13/2015] [Indexed: 12/13/2022]
Abstract
2-arachidonoylglycerol (2-AG) is an endogenous ligand of the cannabinoid CB1 receptor. This endocannabinoid and its hydrolyzing enzyme, monoacylglycerol lipase (MAGL), are present in encephalic regions related to psychiatric disorders, including the midbrain dorsolateral periaqueductal grey (dlPAG). The dlPAG is implicated in panic disorder and its stimulation results in defensive responses proposed as a model of panic attacks. The present work verified if facilitation of 2-AG signalling in the dlPAG counteracts panic-like responses induced by local chemical stimulation. Intra-dlPAG injection of 2-AG prevented panic-like response induced by the excitatory amino acid N-methyl-d-aspartate (NMDA). This effect was mimicked by the 2-AG hydrolysis inhibitor (MAGL preferring inhibitor) URB602. The anti-aversive effect of URB602 was reversed by the CB1 receptor antagonist, AM251. Additionally, a combination of sub-effective doses of 2-AG and URB602 also prevented NMDA-induced panic-like response. Finally, immunofluorescence assay showed a significant increase in c-Fos positive cells in the dlPAG after local administration of NMDA. This response was also prevented by URB602. These data support the hypothesis that 2-AG participates in anti-aversive mechanisms in the dlPAG and reinforce the proposal that facilitation of endocannabinoid signalling could be a putative target for developing additional treatments against panic and other anxiety-related disorders.
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Affiliation(s)
- P H Gobira
- Department of Pharmacology, Institute of Biological Sciences, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901 Belo Horizonte, MG, Brazil
| | - A F Almeida-Santos
- Department of Pharmacology, Institute of Biological Sciences, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901 Belo Horizonte, MG, Brazil
| | - F S Guimaraes
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, SP 14049-900, Brazil; Center of Interdisciplinary Research of Applied Neurosciences (NAPNA), University of São Paulo, Brazil
| | - F A Moreira
- Department of Pharmacology, Institute of Biological Sciences, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901 Belo Horizonte, MG, Brazil
| | - D C Aguiar
- Department of Pharmacology, Institute of Biological Sciences, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901 Belo Horizonte, MG, Brazil
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9
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Uliana DL, Hott SC, Lisboa SF, Resstel LBM. Dorsolateral periaqueductal gray matter CB1 and TRPV1 receptors exert opposite modulation on expression of contextual fear conditioning. Neuropharmacology 2015; 103:257-69. [PMID: 26724373 DOI: 10.1016/j.neuropharm.2015.12.020] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 12/17/2015] [Accepted: 12/18/2015] [Indexed: 12/31/2022]
Abstract
Cannabinoid type 1 (CB1) and Transient Potential Vanilloid type 1 (TRPV1) receptors in the dorsolateral periaqueductal gray (dlPAG) matter are involved in the modulation of conditioned response. Both CB1 and TRPV1 receptors are related to glutamate release and nitric oxide (NO) synthesis. It was previously demonstrated that both NMDA glutamate receptors and NO are involved in the conditioned emotional response. Therefore, one aim of this work was to verify whether dlPAG CB1 and TRPV1 receptors modulate the expression of contextual conditioned emotional response. Moreover, we also investigated the involvement of NMDA receptors and the NO pathway in this response. Male Wistar rats with local dlPAG guide cannula were submitted to contextual fear conditioning. Following 24 h, a polyethylene catheter was implanted in the femoral artery for cardiovascular recordings. After an additional 24 h, drugs were administered in the dlPAG and freezing behavior and autonomic responses were recorded during chamber re-exposure. Both a CB1 antagonist (AM251) and a TRPV1 agonist (Capsaicin; CPS) increased the expression of a conditioned emotional response. This response was prevented by an NMDA antagonist, a preferential neuronal NO synthase inhibitor, an NO scavenger and a soluble guanylate cyclase inhibitor (sGC). Furthermore, pretreatment with a TRPV1 antagonist also prevented the increased conditioned emotional response induced by AM251. Considering that GABA can counterbalance glutamate effects, we also investigated whether GABAA receptors were involved in the effect of a higher dose of AM251. Pretreatment with a GABAA receptor antagonist caused an increased conditioned emotional response by AM251. Our results support the possibility that dlPAG CB1 and TRPV1 receptors are involved in the expression of conditioned emotional response through the NMDA/NO/sGC pathway. Moreover, the opposite effects exerted by GABA and glutamate could produce different outcomes of drugs modulating eCBs.
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Affiliation(s)
- D L Uliana
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Brazil
| | - S C Hott
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Brazil
| | - S F Lisboa
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Brazil.
| | - L B M Resstel
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Brazil.
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10
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Antidepressant-like effects induced by NMDA receptor blockade and NO synthesis inhibition in the ventral medial prefrontal cortex of rats exposed to the forced swim test. Psychopharmacology (Berl) 2015; 232:2263-73. [PMID: 25589143 DOI: 10.1007/s00213-014-3853-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 12/22/2014] [Indexed: 12/21/2022]
Abstract
RATIONALE Systemic treatment with NMDA receptor (NMDAR) antagonists, inhibitors of neuronal nitric oxide synthase (nNOS) or of soluble guanylyl cyclase (sGC), induce antidepressant-like effects in rats. Increased levels of glutamate and nitric oxide (NO) in the medial prefrontal cortex (MPFC) of stressed animals have been described in the literature. However, the role of the NMDAR-nNOS-sGC pathway of the MPFC in the mediation of forced swim-induced behaviors remains unclear. OBJECTIVE The aim of this work was to test the hypothesis that the inhibition of the NMDAR-nNOS-sGC pathway in the ventral MPFC (infralimbic (IL) or prelimbic (PL)) would elicit antidepressant-like effects in the forced swim test (FST). METHODS Rats implanted with cannulae aimed at the PL or the IL were exposed to the FST and injected with LY235959 (NMDAR antagonist), NPA (nNOS inhibitor), ODQ (sGC inhibitor), or carboxy-PTIO (NO scavenger). Additional groups received the AMPA antagonist, NBQX, before the effective doses of LY235959 or NPA. RESULTS LY235959 administration into PL or IL before the FS pretest produced no effects. Administration of LY235959 (3 and 10 nmol/0.2 μL) after pretest was effective only when administered into the PL. However, the administration of NPA (0.01 nmol/0.2 μL), c-PTIO (1.0 nmol/0.2 μL), and ODQ (1.0 nmol/0.2 μL) into the PL or IL before the FST produced antidepressant-like effects. NBQX blocked the antidepressant-like effect of LY235959 but not of NPA. CONCLUSION Blocking NMDAR or NO signaling in the vMPFC, either in the IL or the PL, induces antidepressant-like effects in the rat FST. These effects seemingly occur through independent mechanisms, since NBQX blocked the former effect but not the latter.
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Viana TG, Hott SC, Resstel LB, Aguiar DC, Moreira FA. Anti-aversive role of the endocannabinoid system in the periaqueductal gray stimulation model of panic attacks in rats. Psychopharmacology (Berl) 2015; 232:1545-53. [PMID: 25388290 DOI: 10.1007/s00213-014-3793-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 10/21/2014] [Indexed: 12/28/2022]
Abstract
RATIONALE Direct activation of the cannabinoid CB1 receptor in the dorsolateral periaqueductal gray (dlPAG) inhibits anxiety- and panic-related behaviours in experimental animals. It has remained unclear, however, whether the local endocannabinoid signalling is recruited as a protective mechanism against aversive stimuli. OBJECTIVES The present study tested the hypothesis that the endocannabinoid system counteracts aversive responses in the dlPAG-stimulation model of panic attacks. METHODS All drugs were infused into the dlPAG of rats. Local chemical stimulation with N-methyl-D-aspartate (NMDA, 1 nmol) was employed to induce panic-like behavioural and cardiovascular responses in freely moving and anaesthetized animals, respectively. The neuronal activity in the dlPAG was investigated by c-Fos immunohistochemistry. RESULTS The selective CB1 receptor agonist, ACEA (0.005-0.5 pmol), prevented the NMDA-induced panic-like escape responses. More interestingly, increasing the local levels of endogenous anandamide with a fatty acid amide hydrolase (FAAH) inhibitor, URB597 (0.3-3 nmol), prevented both the behavioural response and the increase in blood pressure induced by NMDA. The effect of URB597 (3 nmol) was reversed by the CB1 receptor antagonist, AM251 (0.1 nmol). Moreover, an otherwise ineffective and sub-threshold dose of NMDA (0.5 nmol) was able to induce a panic-like response if local CB1 receptors were previously blocked by AM251 (0.1 nmol). Finally, URB597 prevented the NMDA-induced neuronal activation of the dlPAG. CONCLUSIONS The endocannabinoid system in the dlPAG attenuates the behavioural, cellular and cardiovascular consequences of aversive stimuli. This process may be considered for the development of additional treatments against panic and other anxiety-related disorders.
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Affiliation(s)
- Thércia G Viana
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil
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Batista LA, Bastos JR, Moreira FA. Role of endocannabinoid signalling in the dorsolateral periaqueductal grey in the modulation of distinct panic-like responses. J Psychopharmacol 2015; 29:335-43. [PMID: 25601395 DOI: 10.1177/0269881114566259] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Panic attacks, a major feature of panic disorder, can be modelled in rats by exposing animals to stimuli that induce escape reactions, such as the elevated T-maze or the activation of the dorsolateral periaqueductal grey. Since the cannabinoid CB1 receptor modulates various types of aversive responses, this study tested the hypothesis that enhancement of endocannabinoid signalling in the dorsolateral periaqueductal grey inhibits panic-like reactions in rats. Local injection of the CB1 agonist, arachidonoyl 2-Chloroethylamide (0.005-0.5 pmol), attenuated the escape response from the open arm of the elevated T-maze, a panicolytic effect. The anandamide hydrolysis inhibitor, URB597 (0.3-3 nmol), did not induce consistent results. In the test of dorsolateral periaqueductal grey stimulation with d,l-homocysteic acid, arachidonoyl 2-Chloroethylamide, at the lowest dose, attenuated the escape reaction. The highest dose of URB597 also inhibited this response, contrary to the result obtained in the elevated T-maze. This effect was reversed by the CB1 antagonist, AM251 (100 pmol). The present results confirm the anti-aversive property of direct CB1 receptor activation in the dorsolateral periaqueductal grey. The effect of the anandamide hydrolysis inhibitor, however, could be detected only in a model employing direct stimulation of this structure. Altogether, these results suggest that anandamide signalling is recruited only under certain types of aversive stimuli.
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Affiliation(s)
- Luara A Batista
- Graduate School in Neuroscience, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Brazil
| | - Juliana R Bastos
- Graduate School in Neuroscience, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Brazil
| | - Fabricio A Moreira
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Brazil
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Gomes FV, Kakihata AM, Semedo ACG, Hott SC, Uliana DL, Guimarães FS, Resstel LBM. D-cycloserine injected into the dorsolateral periaqueductal gray induces anxiolytic-like effects in rats. Behav Brain Res 2014; 271:374-9. [PMID: 24931794 DOI: 10.1016/j.bbr.2014.06.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 06/03/2014] [Accepted: 06/06/2014] [Indexed: 10/25/2022]
Abstract
D-cycloserine (DCS) is a partial agonist of the glycine site coupled to the NMDA receptor (NMDAR). As a consequence, depending on the doses used it can function as an agonist or antagonist at this site. In rodents, anxiolytic-like effects have been observed after the systemic administration of high doses of DCS. The brain sites of these effects have not been investigated. Direct brain injection of glycine site antagonists or agonists into the dorsolateral periaqueductal gray (dlPAG), a brain structure involved in the modulation of defensive-related behaviors, produces anxiolytic- or anxiogenic-like effects, respectively. The present study investigated if the dlPAG could be a brain site of the anxiolytic effects observed after DCS systemic administration. Male Wistar rats received intra-dlPAG injections of DCS (25, 50, 100 or 200 nmol) and were exposed to the elevated plus-maze (EPM) or to the light-dark box. DCS, at the dose of 200 nmol, increased open arm exploration and the time spent in the light compartment, respectively. Based on this result we tested the effects of intra-dlPAG DCS (200 nmol) administration in animals submitted to the Vogel conflict tests. Anxiolytic-like effect was also observed in this test indicated by the increase of punished responses. The drug did not change locomotor activity, discarding potential confounding factors. These results indicated that administration of DCS, a partial agonist of the NMDAR-associated glycine site, into the dlPAG induces anxiolytic-like effects in different models, pointing to a possible site of action of this compound.
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Affiliation(s)
- Felipe V Gomes
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of São Paulo, São Paulo, Brazil.
| | - Alessandra M Kakihata
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Brazil
| | - Ana Carolina G Semedo
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Brazil
| | - Sara C Hott
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Brazil
| | - Daniela L Uliana
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Brazil
| | - Francisco S Guimarães
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of São Paulo, São Paulo, Brazil
| | - Leonardo B M Resstel
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo, Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of São Paulo, São Paulo, Brazil
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Aguiar DC, Hott SC, Deolindo MV, Guimarães FS, Resstel LB. The dorsolateral periaqueductal grey N-methyl-D-aspartate/nitric oxide/cyclic guanosine monophosphate pathway modulates the expression of contextual fear conditioning in rats. J Psychopharmacol 2014; 28:479-85. [PMID: 24008812 DOI: 10.1177/0269881113504012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The dorsolateral periaqueductal grey (dlPAG) plays an essential role in unconditioned fear responses and could also be involved in the expression of contextual fear responses. Activation of glutamate N-methyl-D-aspartate (NMDA) receptors and the nitric oxide (NO) pathway in this region facilitates anxiety-like responses. In the present study we investigated if antagonism of NMDA receptors or inhibition of the NO pathway in the dlPAG would attenuate behavioral and cardiovascular responses of rats submitted to a contextual fear-conditioning paradigm. Male Wistar rats with unilateral cannulae aimed at the dlPAG were re-exposed to a chamber where they had received footshocks 48 h before. Ten min before the test the animals received an intra-dlPAG injection of vehicle, AP7 (NMDA receptor antagonist), N-propyl-L-arginine (neuronal NO synthase inhibitor), carboxy-PTIO (NO scavenger) or 1H-[1,2,4] oxadiazolol [4,3-a]quinoxalin-1-one (ODQ) (guanylate cyclase inhibitor). Freezing and cardiovascular responses were recorded continuously for 10 min. Intra-dlPAG administration of AP7 before re-exposure to the aversively conditioned context attenuated these responses. Similar effects were observed after the NO synthase inhibitor, NO scavenger or guanylate cyclase inhibitor. Our findings suggest that activity of dlPAG NMDA/NO/cyclic guanosine monophosphate (cGMP) pathway facilitates the expression of contextual fear responses.
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Affiliation(s)
- Daniele C Aguiar
- 1Department of Pharmacology, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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Campos AC, Piorino EM, Ferreira FR, Guimarães FS. Increased nitric oxide-mediated neurotransmission in the medial prefrontal cortex is associated with the long lasting anxiogenic-like effect of predator exposure. Behav Brain Res 2013; 256:391-7. [PMID: 23948217 DOI: 10.1016/j.bbr.2013.08.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 07/28/2013] [Accepted: 08/02/2013] [Indexed: 02/03/2023]
Abstract
Posttraumatic stress disorder (PTSD) is an anxiety disorder caused by the experience of a severe traumatic event. In rats this disorder has been modeled by exposure to a predator threat. PTSD has been associated to structural and functional changes in the medial prefrontal cortex (mPFC). Direct injections into this brain region of glutamate antagonists or inhibitors of the nitric oxide synthase (NOS) enzyme cause anxiolytic-like effects in rodents. In the present work we investigated if the behavioral changes induced by predator exposure are associated with changes in the mPFC nitrergic system. Since the hippocampus, amygdala and dorsal periaqueductal grey have also been associated to anxiety disorders, including PTSD, we also verified if this procedure would modify the nitrergic system in these regions. Male Wistar rats were exposed to a dummy or live cat for ten minutes and tested in the elevated plus maze test (EPM) seven days later. Immediately after the test their brains were removed for neuronal NOS (nNOS) immunohistochemistry detection and measurements of nitrite/nitrate (NOx) levels. Exposure to the live cat increased freezing responses. One week later the animals that froze when confronted with the cat presented a decreased percentage of entries in the open arms of the EPM and an increased number of nNOS positive neurons in the mPFC and basolateral nucleus of amygdala, but not in the hippocampus, central and medial nuclei of amygdaloid complex or dorsal-lateral periaqueductal grey. Moreover, cat exposed animals showed increased NOx levels in the mPFC but not in the hippocampus one week later. The number of nNOS neurons and NOx levels in the mPFC showed a significant correlation with freezing time during cat exposure. Our results suggest that plastic modifications of the nitrergic system in the mPFC could be related to long lasting behavioral changes induced by severe traumatic events such as predator exposure.
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Affiliation(s)
- Alline Cristina Campos
- Departament of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of São Paulo, Brazil; Infectious Diseases and Tropical Medicine Program, Medical School, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
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Bonassoli VT, Contardi EB, Milani H, de Oliveira RMW. Effects of nitric oxide synthase inhibition in the dorsolateral periaqueductal gray matter on ethanol withdrawal-induced anxiety-like behavior in rats. Psychopharmacology (Berl) 2013; 228:487-98. [PMID: 23494233 DOI: 10.1007/s00213-013-3049-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Accepted: 02/26/2013] [Indexed: 01/03/2023]
Abstract
RATIONALE Nitric oxide (NO)-mediated transmission in the dorsolateral periaqueductal gray matter (dlPAG) has been involved in the expression of anxiety-like behaviors. Ethanol withdrawal sensitizes the dlPAG and results in increased anxiety-like responses. OBJECTIVES The objective of the study was to test the hypothesis that NO in the dlPAG is involved in the expression of ethanol withdrawal-induced anxiety. METHODS Male Wistar rats were implanted with guide cannulae aimed at the dlPAG. The animals were forced to consume a liquid diet containing ethanol 6-8 % (v/v) for 15 days as their only source of diet. Six days after surgery and 24 h after ethanol discontinuation, the animals received microinjections of the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO), nonselective nitric oxide synthase inhibitor N (G)-nitro-L-arginine methyl ester (L-NAME), selective neuronal nitric oxide synthase inhibitor 1-(2-[trifluoromethyl]phenyl) imidazole (TRIM), or selective inducible nitric oxide synthase (iNOS) inhibitor N-([3-(aminomethyl)phenyl]methyl) ethanimidamide dihydrochloride (1400W) into the dlPAG. Ten minutes later, the animals were tested in the light/dark box. RESULTS Carboxy-PTIO (1 nmol), L-NAME (200 nmol), TRIM (20 nmol), and 1400W (0.3 and 1 nmol) decreased the anxiogenic-like effects of ethanol withdrawal in rats in the light/dark box test. The NO precursor L-arginine reversed the effects of L-NAME. CONCLUSIONS NO production in the dlPAG may play a role in the modulation of ethanol withdrawal-induced anxiety-like behavior in rats. Furthermore, iNOS-mediated NO synthesis in the dlPAG is predominantly involved in the behavioral expression of anxiety-like behavior during ethanol withdrawal.
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Affiliation(s)
- Vivian Taciany Bonassoli
- Department of Pharmacology and Therapeutics, State University of Maringá, Av. Colombo, 5790, CEP 87020-900 Maringá, Paraná, Brazil
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Almeida-Santos AF, Gobira PH, Rosa LC, Guimaraes FS, Moreira FA, Aguiar DC. Modulation of anxiety-like behavior by the endocannabinoid 2-arachidonoylglycerol (2-AG) in the dorsolateral periaqueductal gray. Behav Brain Res 2013; 252:10-7. [PMID: 23714073 DOI: 10.1016/j.bbr.2013.05.027] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 05/16/2013] [Accepted: 05/18/2013] [Indexed: 11/25/2022]
Abstract
Anandamide and 2-arachidonoylglycerol (2-AG) are the two main endocannabinoids, exerting their effects by activating type 1 (CB1r) and type 2 (CB2r) cannabinoid receptors. Anandamide inhibits anxiety-like responses through the activation of CB1r in certain brain regions, including the dorsolateral periaqueductal gray (dlPAG). 2-AG also attenuates anxiety-like responses, although the neuroanatomical sites for these effects remained unclear. Here, we tested the hypothesis that enhancing 2-AG signaling in the dlPAG would induce anxiolytic-like effects. The mechanisms involved were also investigated. Male Wistar rats received intra-dlPAG injections of 2-AG, URB602 (inhibitor of the 2-AG hydrolyzing enzyme, mono-acylglycerol lipase--MGL), AM251 (CB1r antagonist) and AM630 (CB2r antagonist). The behavior was analyzed in the elevated plus maze after the following treatments. Exp. 1: vehicle (veh) or 2-AG (5 pmol, 50 pmol, and 500 pmol). Exp. 2: veh or URB602 (30 pmol, 100 pmol or 300 pmol). Exp. 3: veh or AM251 (100 pmol) followed by veh or 2-AG (50 pmol). Exp. 4: veh or AM630 (1000 pmol) followed by veh or 2-AG. Exp. 5: veh or AM251 followed by veh or URB602 (100 pmol). Exp. 6: veh or AM630 followed by veh or URB602. 2-AG (50 pmol) and URB602 (100 pmol) significantly increased the exploration of the open arms of the apparatus, indicating an anxiolytic-like effect. These behavioral responses were prevented by CB1r (AM251) or CB2r (AM630) antagonists. Our results showed that the augmentation of 2-AG levels in the dlPAG induces anxiolytic-like effects. The mechanism seems to involve both CB1r and CB2r receptors.
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Affiliation(s)
- A F Almeida-Santos
- Department of Pharmacology, Institute of Biological Sciences, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901 Belo Horizonte, MG, Brazil
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Fogaça MV, Gomes FV, Moreira FA, Guimarães FS, Aguiar DC. Effects of glutamate NMDA and TRPV1 receptor antagonists on the biphasic responses to anandamide injected into the dorsolateral periaqueductal grey of Wistar rats. Psychopharmacology (Berl) 2013. [PMID: 23183551 DOI: 10.1007/s00213-012-2927-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
RATIONALE The endocannabinoid and endovanniloid anandamide (AEA) exerts biphasic effects when injected into the dorsolateral periaqueductal grey (dlPAG) in rats submitted to threatening situations. Whereas lower doses of AEA induce anxiolytic-like effects by activating cannabinoid CB1 receptors, no effects are observed with higher doses, possibly due to the simultaneous activation of transient receptor potential vanilloid type 1 (TRPV1) receptors. This activation would facilitate glutamatergic neurotransmission. OBJECTIVE Considering that the blockade of TRPV1 or NMDA receptors in the dlPAG induces anxiolytic-like effects, we tested the hypothesis that facilitation of glutamate transmission through TRPV1 is responsible for the lack of anxiolytic-like effect observed with high AEA doses. METHODS Male Wistar rats with a unilateral cannula aimed at the dlPAG received injections of an ineffective dose of AP7 (an NMDA antagonist, 1 nmol) or capsazepine (CPZ, a TRPV1 antagonist, 10 nmol), followed by a high dose of AEA (50 and 200 pmol) and were exposed to the elevated plus maze (EPM) or the Vogel conflict test (VCT). RESULTS AP7, CPZ, or AEA did not induce any significant effects when administered alone. However, AP7 or CPZ prior to AEA significantly increased the percentage of entries and time spent in the open arms of EPM and the number of punished licks in the VCT suggesting an anxiolytic-like effect. CONCLUSIONS These results suggest that the lack of anxiolytic-like effect of higher AEA doses is due to facilitation of glutamate release in the dlPAG, probably via activation of TRPV1 receptors in this structure.
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Affiliation(s)
- Manoela V Fogaça
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, São Paulo 14049900, Brazil
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Almeida-Santos AF, Moreira FA, Guimarães FS, Aguiar DC. Role of TRPV1 receptors on panic-like behaviors mediated by the dorsolateral periaqueductal gray in rats. Pharmacol Biochem Behav 2013; 105:166-72. [PMID: 23474373 DOI: 10.1016/j.pbb.2013.02.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Revised: 02/18/2013] [Accepted: 02/23/2013] [Indexed: 12/23/2022]
Abstract
The transient receptors potential vanilloid type 1 channels (TRPV1) are expressed in several brain regions related to defensive behaviors, including the dorsolateral periaqueductal gray (dlPAG). The endocannabinoid anandamide, in addition to its agonist activity at cannabinoid type 1 (CB1), is also proposed as an endogenous agonist of these receptors, through which it could facilitate anxiety-like responses. The aim of this work was to test the hypothesis that TRPV1 in the dlPAG of rats would mediate panic-like responses in two models, namely the escape responses induced by chemical stimulation of this structure or by exposure to the elevated T-Maze (ETM). Antagonism of TRPV1 with capsazepine injected into the dlPAG reduced the defense response induced by local NMDA-injection, suggesting an anti-aversive effect. In the ETM, capsazepine inhibited escape response, suggesting a panicolytic-like effect. Interestingly, this effect was prevented by a CB1 antagonist (AM251). The present study showed that antagonism of TRPV1 in the dlPAG induces panicolytic-like effects, which can be prevented by a CB1 antagonist. Therefore, these antiaversive effects of TRPV1 blockade may ultimately occur due to a predominant action of anandamide through CB1 receptors.
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Affiliation(s)
- A F Almeida-Santos
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil
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Baptista D, Nunes-de-Souza RL, Canto-de-Souza A. Activation of 5-HT(2C) receptors in the dorsal periaqueductal gray increases antinociception in mice exposed to the elevated plus-maze. Behav Brain Res 2012; 235:42-7. [PMID: 22800924 DOI: 10.1016/j.bbr.2012.07.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Revised: 06/29/2012] [Accepted: 07/07/2012] [Indexed: 10/28/2022]
Abstract
Several findings have pointed to the role of the dorsal periaqueductal gray (dPAG) serotonin 5-HT(1A) and 5-HT(2A-C) receptor subtypes in the modulation of defensive behavior in animals exposed to the elevated plus-maze (EPM). Besides displaying anxiety-like behavior, rodents also exhibit antinociception in the EPM. This study investigated the effects of intra-dPAG injections of 5-HT(1A) and 5-HT(2B/2C) receptor ligands on EPM-induced antinociception in mice. Male Swiss mice received 0.1 μl intra-dPAG injections of vehicle, 5.6 and 10 nmol of 8-OHDPAT, a 5-HT(1A) receptor agonist (Experiment 1), or 0.01, 0.03 and 0.1 nmol of mCPP, a 5-HT(2B/2C) receptor agonist (Experiment 2). Five minutes later, each mouse received an intraperitoneal injection of 0.6% acetic acid (0.1 ml/10 g body weight; nociceptive stimulus) and was individually confined in the open (OA) or enclosed (EA) arms of the EPM for 5 min, during which the number of abdominal writhes induced by the acetic acid was recorded. While intra-dPAG injection of 8-OHDPAT did not change open-arm antinociception (OAA), mCPP (0.01 nmol) enhanced it. Combined injections of ketanserin (10 nmol/0.1 μl), a 5-HT(2A/2C) receptor antagonist, and 0.01 nmol of mCPP (Experiment 3), selectively and completely blocked the OAA enhancement induced by mCPP. Although intra-dPAG injection of mCPP (0.01 nmol) also produced antinociception in EA-confined mice (Experiment 2), this effect was not confirmed in Experiment 3. Moreover, no other compound changed the nociceptive response in EA-confined animals. These results suggest that the 5-HT(2C) receptors located within the PAG play a role in this type of environmentally induced pain inhibition in mice.
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Affiliation(s)
- Daniela Baptista
- Psychobiology Group, Department of Psychology, CECH-UFSCar, São Carlos, SP 13565-905, Brazil
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Lisboa S, Guimarães F. Differential role of CB1 and TRPV1 receptors on anandamide modulation of defensive responses induced by nitric oxide in the dorsolateral periaqueductal gray. Neuropharmacology 2012; 62:2455-62. [DOI: 10.1016/j.neuropharm.2012.02.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 02/06/2012] [Accepted: 02/10/2012] [Indexed: 12/18/2022]
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Fogaça MV, Lisboa SF, Aguiar DC, Moreira FA, Gomes FV, Casarotto PC, Guimarães FS. Fine-tuning of defensive behaviors in the dorsal periaqueductal gray by atypical neurotransmitters. Braz J Med Biol Res 2012; 45:357-65. [PMID: 22392189 PMCID: PMC3854170 DOI: 10.1590/s0100-879x2012007500029] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2011] [Accepted: 02/23/2012] [Indexed: 11/22/2022] Open
Abstract
This paper presents an up-to-date review of the evidence indicating that atypical neurotransmitters such as nitric oxide (NO) and endocannabinoids (eCBs) play an important role in the regulation of aversive responses in the periaqueductal gray (PAG). Among the results supporting this role, several studies have shown that inhibitors of neuronal NO synthase or cannabinoid type 1 (CB1) receptor agonists cause clear anxiolytic responses when injected into this region. The nitrergic and eCB systems can regulate the activity of classical neurotransmitters such as glutamate and γ-aminobutyric acid (GABA) that control PAG activity. We propose that they exert a ‘fine-tuning’ regulatory control of defensive responses in this area. This control, however, is probably complex, which may explain the usually bell-shaped dose-response curves observed with drugs that act on NO- or CB1-mediated neurotransmission. Even if the mechanisms responsible for this complex interaction are still poorly understood, they are beginning to be recognized. For example, activation of transient receptor potential vanilloid type-1 channel (TRPV1) receptors by anandamide seems to counteract the anxiolytic effects induced by CB1 receptor activation caused by this compound. Further studies, however, are needed to identify other mechanisms responsible for this fine-tuning effect.
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Affiliation(s)
- M V Fogaça
- Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brasil
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Nunes-de-Souza V, Nunes-de-Souza R, Rodgers RJ, Canto-de-Souza A. Blockade of 5-HT2 receptors in the periaqueductal grey matter (PAG) abolishes the anxiolytic-like effect of 5-HT1A receptor antagonism in the median raphe nucleus in mice. Behav Brain Res 2011; 225:547-53. [DOI: 10.1016/j.bbr.2011.07.056] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Revised: 07/26/2011] [Accepted: 07/30/2011] [Indexed: 12/26/2022]
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Blockade of NMDA or NO in the dorsal premammillary nucleus attenuates defensive behaviors. Physiol Behav 2011; 103:279-83. [DOI: 10.1016/j.physbeh.2011.02.034] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2010] [Revised: 02/03/2011] [Accepted: 02/22/2011] [Indexed: 11/20/2022]
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Gualda L, Martins G, Müller B, Guimarães F, Oliveira R. 5-HT1A autoreceptor modulation of locomotor activity induced by nitric oxide in the rat dorsal raphe nucleus. Braz J Med Biol Res 2011; 44:332-6. [DOI: 10.1590/s0100-879x2011007500033] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Accepted: 02/23/2011] [Indexed: 11/22/2022] Open
Affiliation(s)
| | | | - B. Müller
- Universidade Estadual de Maringá, Brasil
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Coutinho MR, Menescal-de-Oliveira L. Role of homocysteic acid in the guinea pig (Cavia porcellus) anterior cingulate cortex in tonic immobility and the influence of NMDA receptors on the dorsal PAG. Behav Brain Res 2009; 208:237-42. [PMID: 19963012 DOI: 10.1016/j.bbr.2009.11.047] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Accepted: 11/30/2009] [Indexed: 10/20/2022]
Abstract
Tonic immobility (TI) is an innate defensive behaviour elicited by physical restriction and postural inversion, and is characterised by a profound and temporary state of akinesis. Our previous studies demonstrated that glutamatergic stimulation of the dorsomedial/dorsolateral portion of periaqueductal gray matter (dPAG) decreases the duration of TI in guinea pigs (Cavia porcellus). Furthermore, evidence suggests that the anterior cingulate cortex (ACC) constitutes an important source of glutamate for the dPAG. Hence, in the current study, we investigated the effects of microinjection of the excitatory amino acid (EAA) agonist DL-homocysteic acid (DLH) and the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 into the ACC on the duration of TI in guinea pigs. We also assessed the effect of the NMDA receptor antagonist (MK-801) into the dorsal periaqueductal gray matter (dPAG) prior to DLH microinjection into the ACC on the TI duration in the guinea pig. Our results demonstrated that DLH microinjections into the ACC decreased the duration of TI. This effect was blocked by previous MK-801 microinjections into the ACC or into the dPAG. The MK-801 microinjections alone did not influence TI duration. These results provide the new insight that EAAs in the ACC can decrease the duration of TI. The mechanism seems to be dependent on the NMDA receptors present in the ACC and in the dPAG.
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Affiliation(s)
- Márcio Ramos Coutinho
- Department of Physiology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, 14049-900 Ribeirão Preto, SP, Brazil
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Tonetto LL, Terzian AL, Del Bel EA, Guimarães FS, Resstel LB. Inhibition of the NMDA receptor/Nitric Oxide pathway in the dorsolateral periaqueductal gray causes anxiolytic-like effects in rats submitted to the Vogel conflict test. Behav Brain Funct 2009; 5:40. [PMID: 19775445 PMCID: PMC2762983 DOI: 10.1186/1744-9081-5-40] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 09/23/2009] [Indexed: 12/03/2022] Open
Abstract
Background Several studies had demonstrated the involvement of the dorsolateral portion of periaqueductal grey matter (dlPAG) in defensive responses. This region contains a significant number of neurons containing the enzyme nitric oxide synthase (NOS) and previous studies showed that non-selective NOS inhibition or glutamate NMDA-receptor antagonism in the dlPAG caused anxiolytic-like effects in the elevated plus maze. Methods In the present study we verified if the NMDA/NO pathway in the dlPAG would also involve in the behavioral suppression observed in rats submitted to the Vogel conflict test. In addition, the involvement of this pathway was investigated by using a selective nNOS inhibitor, Nω-propyl-L-arginine (N-Propyl, 0.08 nmol/200 nL), a NO scavenger, carboxy-PTIO (c-PTIO, 2 nmol/200 nL) and a specific NMDA receptor antagonist, LY235959 (4 nmol/200 nL). Results Intra-dlPAG microinjection of these drugs increased the number of punished licks without changing the number of unpunished licks or nociceptive threshold, as measure by the tail flick test. Conclusion The results indicate that activation of NMDA receptors and increased production of NO in the dlPAG are involved in the anxiety behavior displayed by rats in the VCT.
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Affiliation(s)
- Lucas Lm Tonetto
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Av Bandeirantes 3900, Ribeirão Preto, SP, 14049900, Brazil.
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Aguiar DC, Guimarães FS. Blockade of NMDA receptors and nitric oxide synthesis in the dorsolateral periaqueductal gray attenuates behavioral and cellular responses of rats exposed to a live predator. J Neurosci Res 2009; 87:2418-29. [DOI: 10.1002/jnr.22082] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Alves FH, Crestani CC, Resstel LB, Correa FM. Bed nucleus of the stria terminalis N-methyl-D-aspartate receptors and nitric oxide modulate the baroreflex cardiac component in unanesthetized rats. J Neurosci Res 2009; 87:1703-11. [DOI: 10.1002/jnr.21974] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Terzian ALB, Aguiar DC, Guimarães FS, Moreira FA. Modulation of anxiety-like behaviour by Transient Receptor Potential Vanilloid Type 1 (TRPV1) channels located in the dorsolateral periaqueductal gray. Eur Neuropsychopharmacol 2009; 19:188-95. [PMID: 19064314 DOI: 10.1016/j.euroneuro.2008.11.004] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Revised: 10/29/2008] [Accepted: 11/12/2008] [Indexed: 01/07/2023]
Abstract
The endocannabinoid anandamide is a possible agonist at the Transient Receptor Potential Vanilloid Type 1 (TRPV1) channel, in addition to its agonist activity at cannabinoid type 1 (CB1) receptor. In the midbrain dorsolateral periaqueductal gray (dlPAG) our previous data showed that CB1 activation induces anxiolytic-like effects. However, the role of TRPV1 has remained unclear. Thus, in the present study we tested the hypothesis that this channel would contribute to the modulation of anxiety-like behaviour in the dlPAG. Male Wistar rats received local injections of the TRPV1 antagonist capsazepine (10-60 nmol) and were submitted to the elevated plus-maze (EPM) and to the Vogel test. In addition, animals received local injections of capsaicin (0.01-1 nmol), a TRPV1 agonist, and were tested in the same models. In accordance with our hypothesis, capsazepine produced anxiolytic-like effects both in the EPM and in the Vogel test. Capsaicin mimicked these results, which might be attributed to its ability to quickly desensitize the channel. Altogether, our data suggest that, while CB1 receptors seem to inhibit aversive responses in the dlPAG, TRPV1 could facilitate them. Thus, CB1 and TRPV1 may have opposite functions in modulating anxiety-like behaviour in this region.
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Affiliation(s)
- Ana Luisa B Terzian
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, SP 14049900, Brazil
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Nunes-de-Souza V, Nunes-de-Souza RL, Rodgers RJ, Canto-de-Souza A. 5-HT2 receptor activation in the midbrain periaqueductal grey (PAG) reduces anxiety-like behaviour in mice. Behav Brain Res 2008; 187:72-9. [DOI: 10.1016/j.bbr.2007.08.030] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2007] [Revised: 08/21/2007] [Accepted: 08/23/2007] [Indexed: 12/26/2022]
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Lima VCF, Molchanov ML, Aguiar DC, Campos AC, Guimarães FS. Modulation of defensive responses and anxiety-like behaviors by group I metabotropic glutamate receptors located in the dorsolateral periaqueductal gray. Prog Neuropsychopharmacol Biol Psychiatry 2008; 32:178-85. [PMID: 17804134 DOI: 10.1016/j.pnpbp.2007.08.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 08/01/2007] [Accepted: 08/08/2007] [Indexed: 10/22/2022]
Abstract
Glutamatergic neurotransmission in the dorsolateral periaqueductal gray (dlPAG) is related to defensive responses. However, the role of group I glutamate metabotropic receptors (mGluR) in these responses has been poorly investigated. The objective of the present study, therefore, was to test the hypothesis that interference with group I mGluR-mediated neurotransmission in dlPAG could modulate defensive responses. Male Wistar rats with cannulae aimed at the dlPAG were submitted to the following experiments: 1. intra dlPAG injections of vehicle (veh, 0.2 microL) or (RS)1-aminoindan-1,5-dicarboxylic acid (AIDA, 30-100 nmol, an mGluR1 receptor competitive antagonist) followed, 5 min later, by veh or trans-(+)-1-amino-1,3-ciclopentanedicarboxylic acid (tACPD, a group I and II mGluR agonist, 30 nmol); 2. intra-dlPAG injections of veh, AIDA (30 nmol) or 2-methyl-6-(phenylethynyl)-pyridine (MPEP, an mGluR5 receptor non-competitive antagonist, 50 nmol) followed by trans-azetidine-2,4-dicarboxylic acid (tADA, a group I mGluR agonist, 10 nmol); 3. and 4. intra-dlPAG injections of vehicle, AIDA (10-30 nmol) or MPEP (10-50 nmol) before the elevated plus maze (EPM) test; 5. intra-dlPAG injections of vehicle, AIDA (30 nmol) or MPEP (50 nmol) before the Vogel punished licking test. tACPD induced defensive responses characterized by jumps and an increased number of crossings in the observation box. These responses were attenuated by AIDA (30 nmol). tADA produced similar responses, although of lower intensity. tADA effects were prevented by AIDA and MPEP. Both drugs also produced anxiolytic-like effects in the EPM and Vogel tests when injected alone. The results suggest that group I metabotropic glutamate receptors in the dlPAG facilitate defensive responses and may also be involved in regulating anxiety-like behavior.
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Affiliation(s)
- Vivian C F Lima
- Department of Pharmacology, School of Medicine of Ribeirão Preto Campus, USP, 14049-900, Ribeirão Preto, SP, Brazil
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Resstel LBM, Corrêa FMDA, Guimarães FS. The expression of contextual fear conditioning involves activation of an NMDA receptor-nitric oxide pathway in the medial prefrontal cortex. Cereb Cortex 2007; 18:2027-35. [PMID: 18158326 PMCID: PMC2517108 DOI: 10.1093/cercor/bhm232] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The ventral portion of medial prefrontal cortex (vMPFC) is involved in contextual fear-conditioning expression in rats. In the present study, we investigated the role of local N-methyl-D-aspartic acid (NMDA) glutamate receptors and nitric oxide (NO) in vMPFC on the behavioral (freezing) and cardiovascular (increase of arterial pressure and heart rate) responses of rats exposed to a context fear conditioning. The results showed that both freezing and cardiovascular responses to contextual fear conditioning were reduced by bilateral administration of NMDA receptor antagonist LY235959 (4 nmol/200 nL) into the vMPFC before reexposition to conditioned chamber. Bilateral inhibition of neuronal NO synthase (nNOS) by local vMPFC administration of the Nω-propyl-L-arginine (N-propyl, 0.04 nmol/200 nL) or the NO scavenger carboxy-PTIO (1 nmol/200 nL) caused similar results, inhibiting the fear responses. We also investigated the effects of inhibiting glutamate- and NO-mediated neurotransmission in the vMPFC at the time of aversive context exposure on reexposure to the same context. It was observed that the 1st exposure results in a significant attenuation of the fear responses on reexposure in vehicle-treated animals, which was not modified by the drugs. The present results suggest that a vMPFC NMDA–NO pathway may play an important role on expression of contextual fear conditioning.
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Affiliation(s)
- Leonardo Barbosa Moraes Resstel
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Av. Bandeirantes 3900, 14049-900, Ribeirão Preto, São Paulo, Brazil.
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Tavares RF, Resstel LBM, Corrêa FMA. Interaction between glutamatergic and nitrergic mechanisms mediating cardiovascular responses to l-glutamate injection in the diagonal band of Broca in anesthetized rats. Life Sci 2007; 81:855-62. [PMID: 17761199 DOI: 10.1016/j.lfs.2007.07.028] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Revised: 07/19/2007] [Accepted: 07/30/2007] [Indexed: 11/22/2022]
Abstract
In a previous study, we reported depressor and bradycardiac responses after L-glutamate (L-glu) microinjection into the diagonal band of Broca (dbB) in anesthetized rats. Here, we report the glutamatergic-receptor subtype mediating the cardiovascular effects evoked by L-glu injection into the dbB and the involvement of local nitric oxide (NO) mechanisms as well as peripheral effectors. Microinjections of 100 nL of L-glu (1, 27, 81, 130 or 200 nmol) into the dbB of urethane-anesthetized rats caused short-lasting depressor and bradycardiac responses. Responses were dose-related, with an ED(50) of approximately 81 nmol. This dose was used in later experiments. The cardiovascular responses to L-glu in the dbB were abolished by local pretreatment (100 nL) with the selective N-methyl-D-aspartic acid (NMDA) receptor antagonist LY235959 (4 nmol) but were not affected by pretreatment with the selective non-NMDA receptor antagonist NBQX (4 nmol). Responses to L-glu in the dbB were blocked by local pretreatment with the selective neuronal NO-synthase (nNOS) inhibitor N(omega)-propyl-L-arginine (NPLA, 0.04 nmol); the NO scavenger carboxy-PTIO (C-PTIO, 1 nmol) or the guanylate cyclase inhibitor ODQ (1 nmol). These results suggest that the microinjection of L-glu into the dbB of urethane-anesthetized rats causes dose-related depressor and bradycardiac responses through the NMDA receptor-NO-guanylate cyclase pathway.
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Affiliation(s)
- Rodrigo Fiacadori Tavares
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Av. Bandeirantes, 3900, CEP: 14090-090, Brazil
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