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Falconi-Sobrinho LL, Anjos-Garcia TD, Rebelo MA, Hernandes PM, Almada RC, Tanus-Santos JE, Coimbra NC. The anterior cingulate cortex and its interface with the dorsal periaqueductal grey regulating nitric oxide-mediated panic-like behaviour and defensive antinociception. Neuropharmacology 2024; 245:109831. [PMID: 38160873 DOI: 10.1016/j.neuropharm.2023.109831] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 12/22/2023] [Accepted: 12/23/2023] [Indexed: 01/03/2024]
Abstract
The anterior cingulate cortex (ACC) Cg1 (24b) area modulates glutamate-mediated unconditioned fear and antinociception organised by hypothalamus. However, it remains unknown whether 24b area also modulates these latter defensive responses through connections with the dorsal periaqueductal grey matter (dPAG), a midbrain structure implicated in the genesis of innate fear-induced defence. The aim of this work is to examine the correlation between the behavioural effects of intra-ACC microinjections of vehicle, NMDA (1 nmol) or lidocaine (2%) with Fos protein expression and nitrergic activity in the dPAG of male C57BL/6 mice that were threatened by snakes. In addition, the 24b area-dPAG pathways were also characterised by neural tract tracing procedures. Finally, the effect of dPAG pretreatment with the neuronal nitric oxide synthase inhibitor N(omega)-propyl-l-arginine (NPLA; 0.2, 0.4 or 0.8 nmol) 10 min before 24b area treatment with NMDA on behavioural and nociceptive responses of threatened mice was studied. The activation of 24b area N-methyl-d-aspartic acid receptors facilitated escape and freezing rather than risk assessment, and enhanced Fos expression and nitrite levels in dPAG, while lidocaine decreased escape and risk assessment as well as Fos and nitrergic activity in dPAG. In addition, dPAG pretreatment with NPLA suppressed intra-24b NMDA-facilitated panicogenic effects while increased nociception. Infusions of an antegrade neurotracer into 24b area showed axonal fibres surrounding both dorsomedial and dorsolateral PAG perikarya. Neurons were identified in 24b area after deposits of a retrograde neurotracer into dPAG. Our findings suggest that the ACC/24b area modulates innate defensive responses through the recruitment of dPAG nitrergic neurons.
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Affiliation(s)
- Luiz Luciano Falconi-Sobrinho
- Laboratory of Neuroanatomy and Neuropsychobiology, Department of Pharmacology, Ribeirão Preto Medical School of the University of São Paulo (USP), Av. Bandeirantes 3900, Ribeirão Preto, São Paulo, 14049-900, Brazil; Behavioural Neurosciences Institute (INeC), Psychobiology Division, Av. Bandeirantes, 3900, Ribeirão Preto, 14049-900, São Paulo, Brazil.
| | - Tayllon Dos Anjos-Garcia
- Laboratory of Neuroanatomy and Neuropsychobiology, Department of Pharmacology, Ribeirão Preto Medical School of the University of São Paulo (USP), Av. Bandeirantes 3900, Ribeirão Preto, São Paulo, 14049-900, Brazil; Biomedical Sciences Institute of the Federal University of Alfenas (UNIFAL), Alfenas, Minas Gerais, Brazil
| | - Macário Arosti Rebelo
- Laboratory of Cardiovascular Pharmacology, Department of Pharmacology, Ribeirão Preto Medical School of the University of São Paulo (USP), Av. Bandeirantes 3900, Ribeirão Preto, São Paulo, 14049-900, Brazil
| | - Paloma Molina Hernandes
- Laboratory of Neurobiology and Neurobiotechnology, Department of Biological Sciences, School of Science, Humanities and Languages, São Paulo State University (UNESP), Assis, São Paulo, Brazil
| | - Rafael Carvalho Almada
- Behavioural Neurosciences Institute (INeC), Psychobiology Division, Av. Bandeirantes, 3900, Ribeirão Preto, 14049-900, São Paulo, Brazil; Laboratory of Neurobiology and Neurobiotechnology, Department of Biological Sciences, School of Science, Humanities and Languages, São Paulo State University (UNESP), Assis, São Paulo, Brazil
| | - Jose Eduardo Tanus-Santos
- Laboratory of Cardiovascular Pharmacology, Department of Pharmacology, Ribeirão Preto Medical School of the University of São Paulo (USP), Av. Bandeirantes 3900, Ribeirão Preto, São Paulo, 14049-900, Brazil
| | - Norberto Cysne Coimbra
- Laboratory of Neuroanatomy and Neuropsychobiology, Department of Pharmacology, Ribeirão Preto Medical School of the University of São Paulo (USP), Av. Bandeirantes 3900, Ribeirão Preto, São Paulo, 14049-900, Brazil; Behavioural Neurosciences Institute (INeC), Psychobiology Division, Av. Bandeirantes, 3900, Ribeirão Preto, 14049-900, São Paulo, Brazil.
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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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Wang Y, Han J, Zhu J, Zhang M, Ju M, Du Y, Tian Z. GluN2A/ERK/CREB Signaling Pathway Involved in Electroacupuncture Regulating Hypothalamic-Pituitary-Adrenal Axis Hyperactivity. Front Neurosci 2021; 15:703044. [PMID: 34658758 PMCID: PMC8514998 DOI: 10.3389/fnins.2021.703044] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 09/09/2021] [Indexed: 12/05/2022] Open
Abstract
The hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis caused by stress will inevitably disrupt the homeostasis of the neuroendocrine system and damage physiological functions. It has been demonstrated that electroacupuncture (EA) can modulate HPA axis hyperactivity during the perioperative period. As the initiating factor of the HPA axis, hypothalamic corticotrophin-releasing hormone (CRH) is the critical molecule affected by EA. However, the mechanism by which EA reduces CRH synthesis and secretion remains unclear. Activated N-methyl-D-aspartate receptor (NMDAR) has been linked to over-secretion of hypothalamic CRH induced by stress. To determine whether NMDAR is involved in EA regulating the over-expression of CRH, a surgical model of partial hepatectomy (HT) was established in our experiment. The effect of EA on hypothalamic NMDAR expression in HT mice was examined. Then, we investigated whether the extracellular regulated protein kinases (ERK)/cyclic adenosine monophosphate response element-binding protein (CREB) signaling pathway mediated by NMDAR was involved in EA regulating HPA axis hyperactivity. It was found that surgery enhanced the expression of hypothalamic CRH and caused HPA axis hyperactivity. Intriguingly, EA effectively suppressed the expression of CRH and decreased the activation of GluN2A (NMDAR subunit), ERK, and CREB in HT mice. GluN2A, ERK, and CREB antagonists had similar effects on normalizing the expression of CRH and HPA axis function compared with EA. Our findings suggested that surgery enhanced the activation of the hypothalamic GluN2A/ERK/CREB signaling pathway, thus promoting the synthesis and secretion of CRH. EA suppressed the phosphorylation of GluN2A, ERK, and CREB in mice that had undergone surgery, indicating that the GluN2A/ERK/CREB signaling pathway was involved in EA alleviating HPA axis hyperactivity.
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Affiliation(s)
- Yu Wang
- State Key Laboratory of Medical Neurobiology, Department of Integrative Medicine and Neurobiology, Brain Science Collaborative Innovation Center, School of Basic Medical Sciences, Institutes of Brain Science, Fudan Institutes of Integrative Medicine, Fudan University, Shanghai, China
| | - Jing Han
- State Key Laboratory of Medical Neurobiology, Department of Integrative Medicine and Neurobiology, Brain Science Collaborative Innovation Center, School of Basic Medical Sciences, Institutes of Brain Science, Fudan Institutes of Integrative Medicine, Fudan University, Shanghai, China
| | - Jing Zhu
- Department of Anatomy, School of Basic Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Mizhen Zhang
- State Key Laboratory of Medical Neurobiology, Department of Integrative Medicine and Neurobiology, Brain Science Collaborative Innovation Center, School of Basic Medical Sciences, Institutes of Brain Science, Fudan Institutes of Integrative Medicine, Fudan University, Shanghai, China
| | - Minda Ju
- State Key Laboratory of Medical Neurobiology, Department of Integrative Medicine and Neurobiology, Brain Science Collaborative Innovation Center, School of Basic Medical Sciences, Institutes of Brain Science, Fudan Institutes of Integrative Medicine, Fudan University, Shanghai, China
| | - Yueshan Du
- State Key Laboratory of Medical Neurobiology, Department of Integrative Medicine and Neurobiology, Brain Science Collaborative Innovation Center, School of Basic Medical Sciences, Institutes of Brain Science, Fudan Institutes of Integrative Medicine, Fudan University, Shanghai, China
| | - Zhanzhuang Tian
- State Key Laboratory of Medical Neurobiology, Department of Integrative Medicine and Neurobiology, Brain Science Collaborative Innovation Center, School of Basic Medical Sciences, Institutes of Brain Science, Fudan Institutes of Integrative Medicine, Fudan University, Shanghai, China
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Li MM, Zhou P, Chen XD, Xu HS, Wang J, Chen L, Zhang N, Liu N. NO in the dPAG modulates panic-like responses and ASIC1a expression in the prefrontal cortex and hippocampus in mice. Biochem Biophys Res Commun 2019; 511:274-279. [PMID: 30770101 DOI: 10.1016/j.bbrc.2019.02.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Accepted: 02/04/2019] [Indexed: 01/20/2023]
Abstract
Panic disorder (PD) is a multifactorial neuropsychiatric disorder. Our previous study has demonstrated that the nitric oxide (NO) pathway and the acid-sensing ion channel 1a (ASIC1a) level in the dorsal midbrain periaqueductal gray (dPAG) are involved in the modulation of panic-like responses. In addition, the prefrontal cortex (PFC) and the hippocampus also play a role in panic-like responses. However, no studies have investigated the protein level of ASIC1a in the PFC and hippocampus in a mouse model of panic-like disorders after alteration of the NO pathway in the dPAG. We investigated the production of a panic attack with intra-dPAG injections of SNAP, an NO donor, and 7-NI, an nNOS inhibitor. Moreover, we measured ASIC1a protein levels in the PFC and hippocampus. The rat exposure test (RET) is frequently used as an animal model of panic. In our study, C57BL/6 mice received an intra-dPAG injection of SNAP or 7-NI before RET; neurobehavioral tests were then conducted, followed by mechanistic evaluation through western blot analysis in the PFC and hippocampus. An intra-dPAG infusion of SNAP significantly increased the panic-like effect, whereas treatment with 7-NI decreased fear behavior. Mice treated with SNAP/7-NI showed significantly increased/decreased ASIC1a expression in the PFC, and a decreasing/increasing trend in the hippocampus. The present study suggests that the NO pathway in the dPAG plays a key role in panic-like responses in mice confronted by a rat, further, NO intra-dPAG injection also modulates the ASIC1a expression levels in the PFC and hippocampus.
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Affiliation(s)
- Meng-Meng Li
- Medical School, Nanjing University, Nanjing, 210093, China
| | - Ping Zhou
- Department of Medical Psychology, Nanjing Medical University, Affiliated Nanjing Brain Hospital, Nanjing, 210029, China
| | - Xiao-Dong Chen
- Department of Anesthesiology, The First Affiliated Hospital of Nanjing Medical University, 210029, China
| | - Huai-Sha Xu
- Medical School, Nanjing University, Nanjing, 210093, China
| | - Jun Wang
- Department of Toxicology, The Key Lab of Modern Toxicology (NJMU), Ministry of Education, School of Public Health, Nanjing Medical University, Nanjing, 211166, China
| | - Ling Chen
- State Key Laboratory of Reproductive Medicine, Department of Physiology, Nanjing Medical University, Nanjing, 211166, China
| | - Ning Zhang
- Department of Medical Psychology, Nanjing Medical University, Affiliated Nanjing Brain Hospital, Nanjing, 210029, China
| | - Na Liu
- Department of Medical Psychology, Nanjing Medical University, Affiliated Nanjing Brain Hospital, Nanjing, 210029, China.
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Zare A, Jahanshahi A, Rahnama'i MS, Schipper S, van Koeveringe GA. The Role of the Periaqueductal Gray Matter in Lower Urinary Tract Function. Mol Neurobiol 2018; 56:920-934. [PMID: 29804231 PMCID: PMC6400878 DOI: 10.1007/s12035-018-1131-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 05/14/2018] [Indexed: 12/18/2022]
Abstract
The periaqueductal gray matter (PAG), as one of the mostly preserved evolutionary components of the brain, is an axial structure modulating various important functions of the organism, including autonomic, behavioral, pain, and micturition control. It has a critical role in urinary bladder physiology, with respect to storage and voiding of urine. The PAG has a columnar composition and has extensive connections with its cranially and caudally located components of the central nervous system (CNS). The PAG serves as the control tower of the detrusor and sphincter contractions. It serves as a bridge between the evolutionary higher decision-making brain centers and the lower centers responsible for reflexive micturition. Glutamatergic cells are the main operational neurons in the vlPAG, responsible for the reception and relay of the signals emerging from the bladder, to related brain centers. Functional imaging studies made it possible to clarify the activity of the PAG in voiding and filling phases of micturition, and its connections with various brain centers in living humans. The PAG may be affected in a wide spectrum of disorders, including multiple sclerosis (MS), migraine, stroke, Wernicke’s encephalopathy, and idiopathic normal pressure hydrocephalus, all of which may have voiding dysfunction or incontinence, in certain stages of the disease. This emphasizes the importance of this structure for the basic understanding of voiding and storage disorders and makes it a potential candidate for diagnostic and therapeutic interventions.
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Affiliation(s)
- Aryo Zare
- Department of Urology, Maastricht University Medical Center, Maastricht, The Netherlands.
- School for Mental Health and Neuroscience, Faculty of Health, Medicine and Life Science, Maastricht, The Netherlands.
| | - Ali Jahanshahi
- School for Mental Health and Neuroscience, Faculty of Health, Medicine and Life Science, Maastricht, The Netherlands
- Department of Neurosurgery, Maastricht University Medical Center, Maastricht, The Netherlands
| | | | - Sandra Schipper
- Department of Urology, Maastricht University Medical Center, Maastricht, The Netherlands
- School for Mental Health and Neuroscience, Faculty of Health, Medicine and Life Science, Maastricht, The Netherlands
| | - Gommert A van Koeveringe
- Department of Urology, Maastricht University Medical Center, Maastricht, The Netherlands.
- School for Mental Health and Neuroscience, Faculty of Health, Medicine and Life Science, Maastricht, The Netherlands.
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Siba IP, Bortolanza M, Frazão Vital MAB, Andreatini R, da Cunha JM, Del Bel EA, Zanoveli JM. Fish oil prevents rodent anxious states comorbid with diabetes: A putative involvement of nitric oxide modulation. Behav Brain Res 2017; 326:173-186. [DOI: 10.1016/j.bbr.2017.03.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 03/02/2017] [Accepted: 03/04/2017] [Indexed: 01/17/2023]
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Kim DJ, Lee AS, Yttredahl AA, Gómez-Rodríguez R, Anderson BJ. Repeated threat (without direct harm) alters metabolic capacity in select regions that drive defensive behavior. Neuroscience 2017; 353:106-118. [PMID: 28433648 DOI: 10.1016/j.neuroscience.2017.04.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 04/07/2017] [Accepted: 04/10/2017] [Indexed: 10/19/2022]
Abstract
To understand the behavioral consequences of intermittent anticipatory stress resulting from threats without accompanying physiological challenges, we developed a semi-naturalistic rodent housing and foraging environment that can include threats that are unpredictable in timing. Behavior is automatically recorded while rats forage for food or water. Over three weeks, the threats have been shown to elicit risk assessment behaviors, increase defensive burying and increase adrenal gland weight. To identify brain regions activated by this manipulation, we measured cytochrome c oxidase (COX), which is tightly coupled to neural activity. Adolescent male Sprague-Dawley rats were randomly assigned to control (CT) or unpredictable threat/stress (ST) housing conditions consisting of two tub cages, one with food and another with water, separated by a tunnel. Over three weeks (P31-P52), the ST group received randomly timed (probability of 0.25), simultaneous presentations of ferret odor, an abrupt light, and sound at the center of the tunnel. The ST group had consistently fewer tunnel crossings than the CT group, but similar body weights. Group differences in COX activity were detected in regions implicated in the control of defensive burying. There was an increase in COX activity in the hypothalamic premammillary dorsal nucleus (PMD) and lateral septum (LS), whereas a decrease was observed in the periaqueductal gray (PAG) and CA3 region of the hippocampus. There were no significant differences in the anterior cingulate cortex, prefrontal cortex, striatum or motor cortex. The sites with changes in metabolic capacity are candidates for the sites of plasticity that may underlie the behavioral adaptations to intermittent threats.
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Affiliation(s)
- D J Kim
- Department of Psychology, Stony Brook University, Stony Brook, NY 11794-5230, United States; Graduate Program in Integrative Neuroscience, Stony Brook University, Stony Brook, NY 11794-5230, United States
| | - A S Lee
- Department of Psychology, Stony Brook University, Stony Brook, NY 11794-5230, United States
| | - A A Yttredahl
- Department of Psychology, Stony Brook University, Stony Brook, NY 11794-5230, United States; Graduate Program in Integrative Neuroscience, Stony Brook University, Stony Brook, NY 11794-5230, United States
| | - R Gómez-Rodríguez
- Department of Psychology, Stony Brook University, Stony Brook, NY 11794-5230, United States
| | - B J Anderson
- Department of Psychology, Stony Brook University, Stony Brook, NY 11794-5230, United States; Graduate Program in Integrative Neuroscience, Stony Brook University, Stony Brook, NY 11794-5230, United States.
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Souza RR, Carobrez AP. Acquisition and expression of fear memories are distinctly modulated along the dorsolateral periaqueductal gray axis of rats exposed to predator odor. Behav Brain Res 2016; 315:160-7. [PMID: 27522018 DOI: 10.1016/j.bbr.2016.08.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 08/04/2016] [Accepted: 08/09/2016] [Indexed: 12/27/2022]
Abstract
The dorsolateral region of the midbrain periaqueductal gray (dlPAG) modulates both innate and conditioned fear responses. However, the contribution of the rostrocaudal portions of the dlPAG to defense reactions and aversive memories remains unclear. Here, we sought to investigate the effects of N-methyl-d-aspartate (NMDA) receptor blockade within rostral or caudal dlPAG of rats exposed to innate and learned fear to cat odor. For this, adult male Wistar rats were microinjected with the NMDA antagonist D-2-amino-5-phosphono-pentanoate (AP5; 3 or 6nmol/0.2μl) into the rostral or caudal dlPAG before and after the exposure to the cat odor or to the context paired with the predator odor. The results demonstrated that cat odor exposure induced unconditioned defensive behaviors as well as contextual fear. AP5 microinjected in the rostral dlPAG reduced the defensive responses to cat odor and impaired the acquisition, but not consolidation of contextual fear. On the other hand, AP5 infused within the caudal dlPAG promoted long-lasting reduction of contextual fear expression. Altogether, our data suggest that NMDA receptors mediate a functional dichotomy in the rostrocaudal axis of dlPAG regulating unconditioned and conditioned defensive reactions to predatory cues.
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Affiliation(s)
- Rimenez R Souza
- Departamento de Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - Antonio P Carobrez
- Departamento de Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil.
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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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10
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Batista PA, Fogaça MV, Guimarães FS. The endocannabinoid, endovanilloid and nitrergic systems could interact in the rat dorsolateral periaqueductal gray matter to control anxiety-like behaviors. Behav Brain Res 2015; 293:182-8. [PMID: 26187694 DOI: 10.1016/j.bbr.2015.07.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 07/01/2015] [Accepted: 07/04/2015] [Indexed: 12/21/2022]
Abstract
Cannabinoid compounds usually produce biphasic effects in the modulation of emotional responses. Low doses of the endocannabinoid anandamide (AEA) injected into the dorsolateral periaqueductal gray matter (dlPAG) induce anxiolytic-like effects via CB1 receptors activation. However, at higher doses the drug loses this effect, in part by activating Transient Receptor Potential Vanilloid Type 1 (TRPV1). Activation of these latter receptors could induce the formation of nitric oxide (NO). Thus, the present study tested the hypothesis that at high doses AEA loses it anxiolytic-like effect by facilitating, probably via TRPV1 receptor activation, the formation of NO. Male Wistar rats received combined injections into the dlPAG of vehicle, the TRPV1 receptor antagonist 6-iodo-nordihydrocapsaicin or the NO scavenger carboxy-PTIO (c-PTIO), followed by vehicle or AEA, and were submitted to the elevated plus maze (EPM) or the Vogel conflict test (VCT). A low dose (5pmol) of AEA produced an anxiolytic-like effect that disappeared at higher doses (50 and 200pmol). The anxiolytic-like effects of these latter doses, however, were restored after pre-treatment with a low and ineffective dose of c-PTIO in both animal models. In addition, the combined administration of ineffective doses of 6-iodo-nordihydrocapsaicin (1nmol) and c-PTIO (0.3nmol) produced an anxiolytic-like response. Therefore, these results support the hypothesis that intra-dlPAG injections of high doses of AEA lose their anxiolytic effects by favoring TRPV1 receptors activity and consequent NO formation, which in turn could facilitate defensive responses.
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Affiliation(s)
- Priscila A Batista
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo (FMRP-USP), Bandeirantes Avenue, 3900, Ribeirão Preto, 14049-900 São Paulo, Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of São Paulo (USP), Brazil
| | - Manoela V Fogaça
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo (FMRP-USP), Bandeirantes Avenue, 3900, Ribeirão Preto, 14049-900 São Paulo, Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of São Paulo (USP), Brazil.
| | - Francisco S Guimarães
- Department of Pharmacology, Medical School of Ribeirão Preto, University of São Paulo (FMRP-USP), Bandeirantes Avenue, 3900, Ribeirão Preto, 14049-900 São Paulo, Brazil; Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of São Paulo (USP), Brazil
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11
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Barbaresi P, Mensà E, Lariccia V, Pugnaloni A, Amoroso S, Fabri M. Differential distribution of parvalbumin- and calbindin-D28K-immunoreactive neurons in the rat periaqueductal gray matter and their colocalization with enzymes producing nitric oxide. Brain Res Bull 2013; 99:48-62. [PMID: 24107244 DOI: 10.1016/j.brainresbull.2013.09.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 09/09/2013] [Accepted: 09/17/2013] [Indexed: 10/26/2022]
Abstract
The distribution, colocalization with enzymes producing nitric oxide (NO), and the synaptic organization of neurons containing two calcium-binding proteins (CaBPs) - parvalbumin (Parv) and calbindin-D28K (Calb) - were investigated in the rat periaqueductal gray matter (PAG). Parv-immunopositive (ParvIP) neurons were detected in the mesencephalic nucleus and rarely in the PAG. CalbIP neurons were found both in the dorsolateral (PAG-dl) and ventrolateral PAG (PAG-vl); their size ranged from 112.96 μm(2) (PAG-dl) to 125.13 μm(2) (PAG-vl). Ultrastructurally Parv and Calb immunoreactivity was mostly found in dendritic profiles. Axon terminals containing each of the two CaBPs formed symmetric synapses. Moreover both Parv and Calb were used to label a subpopulation of NO-producing neurons. Colocalization was investigated using two protocols: (i) a combination of Calb and Parv immunocytochemistry (Icc) with nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry (Hi) and (ii) neuronal NO synthase-Icc (nNOS) (immunofluorescence). Both techniques demonstrated a complete lack of colocalization of Parv and NADPH-d/nNOS in PAG neurons. Double-labeled (DL) neurons (Calb-NADPH-d; Calb-nNOS) were detected in PAG-dl. NADPH-d-Hi/Calb-Icc indicated that 41-47% of NADPH-d-positive neurons contained Calb, whereas 17-23% of CalbIP cells contained NADPH-d. Two-color immunofluorescence revealed that 53-66% of nNOSIP cells colocalized with Calb and 24-34% of CalbIP neurons contained nNOS. DL neuron size was 104.44 μm(2); neurons labeled only with NADPH-d or Calb measured 89.793 μm(2) and 113.48 μm(2), respectively. Together with previous findings (Barbaresi et al. [2012]) these data suggest that: Therefore the important aspect of the PAG intrinsic organization emerging from this and previous double-labeling studies is the chemical diversity of NO-synthesizing neurons, which is likely related to the different functions in which these neurons are involved.
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Affiliation(s)
- Paolo Barbaresi
- Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Marche Polytechnic University, I-60020 Ancona, Italy.
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Mascarenhas DC, Gomes KS, Nunes-de-Souza RL. Anxiogenic-like effect induced by TRPV1 receptor activation within the dorsal periaqueductal gray matter in mice. Behav Brain Res 2013; 250:308-15. [PMID: 23707246 DOI: 10.1016/j.bbr.2013.05.023] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 05/03/2013] [Accepted: 05/14/2013] [Indexed: 01/17/2023]
Abstract
Pharmacological manipulation of TRPV1 (Transient Receptor Potential Vanilloid type-1) receptors has been emerging as a novel target in the investigation of anxiety states. Here, we attempt to show the role played by the TRPV1 receptors within the dorsal periaqueductal gray matter (dPAG), a midbrain structure strongly involved in the modulation of anxiety. Anxiety was assessed by recording spatiotemporal [percent open arm entries (%OE) and percent open arm time (%OT)] and ethological [e.g., head dipping (HD), stretched-attend postures (SAP)] measures in mice exposed to the elevated plus-maze (EPM). Mice received an intra-dPAG injection of the TRPV1 agonist capsaicin (0, 0.01, 0.1 or 1.0nmol/0.2μL; Experiment 1) or antagonist capsazepine (0, 10, 30 or 60nmol/0.2μL; Experiment 2), or combined injections of capsazepine (30nmol) and capsaicin (1.0nmol) (Experiment 3), and were exposed to the EPM to record spatiotemporal and ethological measures. While capsaicin produced an anxiogenic-like effect (it reduced %OE and %OT and frequency of SAP and HD in the open arms), capsazepine did not change any behavior in the EPM. However, when injected before capsaicin (1.0nmol), intra-dPAG capsazepine (30nmol-a dose devoid of intrinsic effects) antagonized completely the anxiogenic-like effect of the TRPV1 agonist. These results suggest that the anxiogenic-like effect produced by capsaicin is primarily due to TRPV1 activation within the dPAG in mice, but that dPAG TRPV1 receptors do not exert a tonic control over defensive behavior in mice exposed to the EPM.
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13
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Campos KFC, Amaral VCS, Rico JL, Miguel TT, Nunes-de-Souza RL. Ethopharmacological evaluation of the rat exposure test: a prey-predator interaction test. Behav Brain Res 2012. [PMID: 23195112 DOI: 10.1016/j.bbr.2012.11.023] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The rat exposure test (RET) is a prey (mouse)-predator (rat) situation that activates brain defensive areas and elicits hormonal and defensive behavior in the mouse. Here, we investigated possible correlations between the spatiotemporal [time spent in protected (home chamber and tunnel) and unprotected (surface) compartments and frequency of entries into the three compartments] and ethological [e.g., duration of protected and unprotected stretched-attend postures (SAP), duration of contact with the rat's compartment] measures (Experiment 1). Secondly, we investigated the effects of systemic treatment with pro- or anti-aversive drugs on the behavior that emerged from the factor analysis (Experiment 2). The effects of chronic (21 days) imipramine and fluoxetine on defensive behavior were also investigated (Experiment 3). Exp. 1 revealed that the time in the protected compartment, protected SAP and rat contacts loaded on factor 1 (defensive behavior), while the total entries and unprotected SAP loaded on factor 2 (locomotor activity). Exp. 2 showed that alprazolam (but not diazepam) selectively changed the defensive factor. Caffeine produced a mild proaversive-like effect, whereas yohimbine only decreased locomotor activity (total entries). Fluoxetine (but not imipramine) produced a weak proaversive-like effect. 5-HT(1A)/5-HT(2) receptor ligands did not change any behavioral measure. In Exp. 3, chronic fluoxetine (but not imipramine) attenuated the defensive behavior factor without changing locomotion. Given that the defensive factor was sensitive to drugs known to attenuate (alprazolam and chronic fluoxetine) and induce (caffeine) panic attack, we suggest the RET as a useful test to assess the effects of panicolytic and panicogenic drugs.
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Affiliation(s)
- Kelciane Ferreira Caetano Campos
- Laboratory of Pharmacology, School of Pharmaceutical Sciences, Universidade Estadual Paulista, UNESP, Araraquara, SP 14801-902, Brazil
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Hahn JD, Swanson LW. Connections of the lateral hypothalamic area juxtadorsomedial region in the male rat. J Comp Neurol 2012; 520:1831-90. [PMID: 22488503 DOI: 10.1002/cne.23064] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The connections of the lateral hypothalamic area juxtadorsomedial region (LHAjd) were investigated in a series of pathway-tracing experiments involving iontophoretic co-injection of the tracers Phaseolus vulgaris-leucoagglutinin (PHA-L; for outputs) and cholera toxin B subunit (CTB; for inputs). Results revealed that the LHAjd has connections with some 318 distinct gray matter regions encompassing all four subsystems-motor, sensory, cognitive, and behavioral state-included in a basic structure-function network model of the nervous system. Integration of these subsystems is necessary for the coordination and control of emotion and behavior, and in that regard the connections of the LHAjd indicate that it may have a prominent role. Furthermore, the LHAjd connections, together with the connections of other LHA differentiations studied similarly to date, indicate a distinct topographic organization that suggests each LHA differentiation has specifically differing degrees of involvement in the control of multiple behaviors. For the LHAjd, its involvement to a high degree in the control of defensive behavior, and to a lesser degree in the control of other behaviors, including ingestive and reproductive, is suggested. Moreover, the connections of the LHAjd suggest that its possible role in the control of these behaviors may be very broad in scope because they involve the somatic, neuroendocrine, and autonomic divisions of the nervous system. In addition, we suggest that connections between LHA differentiations may provide, at the level of the hypothalamus, a neuronal substrate for the coordinated control of multiple themes in the behavioral repertoire.
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Affiliation(s)
- Joel D Hahn
- Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520, USA.
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Miguel TT, Gomes KS, Nunes-de-Souza RL. Contrasting effects of nitric oxide and corticotropin- releasing factor within the dorsal periaqueductal gray on defensive behavior and nociception in mice. Braz J Med Biol Res 2012; 45:299-307. [PMID: 22450373 PMCID: PMC3854172 DOI: 10.1590/s0100-879x2012007500043] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2011] [Accepted: 03/14/2012] [Indexed: 01/28/2024] Open
Abstract
The anxiogenic and antinociceptive effects produced by glutamate N-methyl-D-aspartate receptor activation within the dorsal periaqueductal gray (dPAG) matter have been related to nitric oxide (NO) production, since injection of NO synthase (NOS) inhibitors reverses these effects. dPAG corticotropin-releasing factor receptor (CRFr) activation also induces anxiety-like behavior and antinociception, which, in turn, are selectively blocked by local infusion of the CRF type 1 receptor (CRFr1) antagonist, NBI 27914 [5-chloro-4-(N-(cyclopropyl)methyl-N-propylamino)-2-methyl-6-(2,4,6-trichlorophenyl)aminopyridine]. Here, we determined whether i) the blockade of the dPAG by CRFr1 attenuates the anxiogenic/antinociceptive effects induced by local infusion of the NO donor, NOC-9 [6-(2-hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-hexanamine], and ii) the anxiogenic/antinociceptive effects induced by intra-dPAG CRF are prevented by local infusion of N(ω)-propyl-L-arginine (NPLA), a neuronal NOS inhibitor, in mice. Male Swiss mice (12 weeks old, 25-35 g, N = 8-14/group) were stereotaxically implanted with a 7-mm cannula aimed at the dPAG. Intra-dPAG NOC-9 (75 nmol) produced defensive-like behavior (jumping and running) and antinociception (assessed by the formalin test). Both effects were reversed by prior local infusion of NBI 27914 (2 nmol). Conversely, intra-dPAG NPLA (0.4 nmol) did not modify the anxiogenic/antinociceptive effects of CRF (150 pmol). These results suggest that CRFr1 plays an important role in the defensive behavior and antinociception produced by NO within the dPAG. In contrast, the anxiogenic and antinociceptive effects produced by intra-dPAG CRF are not related to NO synthesis in this limbic midbrain structure.
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Affiliation(s)
- T T Miguel
- Programa Interinstitucional de Pós-Graduação em Ciências Fisiológicas, Universidade Federal de São Carlos, Araraquara, SP, Brasil
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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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Barbaresi P, Quaranta A, Amoroso S, Mensà E, Fabri M. Immunocytochemical localization of calretinin-containing neurons in the rat periaqueductal gray and colocalization with enzymes producing nitric oxide: a double, double-labeling study. Synapse 2011; 66:291-307. [PMID: 22121011 DOI: 10.1002/syn.21509] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 11/11/2011] [Indexed: 11/06/2022]
Abstract
The pattern of distribution and colocalization of the calcium-binding protein calretinin (Cal) and of enzymes producing nitric oxide (NO) was examined in the rat periaqueductal gray matter (PAG) using two different experimental approaches, by combining Cal immunocytochemistry with NADPH-diaphorase (NADPH-d) histochemistry and with NOS immunocytochemistry, respectively. Cal-immunopositive neurons were found throughout the rostrocaudal extension of both dorsolateral (PAG-dl) and ventrolateral PAG (PAG-vl). Double-labeled neurons were found only in PAG-dl. The first experimental approach indicated that 33-41% of the NADPH-d-positive (Nadph+) cells were immunoreactive for Cal, whereas NADPH-d activity appeared in 19-26% of the Cal-immunopositive (Cal(IP) ) neurons. Two-color immunofluorescence revealed that ∼39-43% of NOS-immunoreactive (NOS(IR) ) neurons were double-labeled with Cal and ∼23% of Cal(IP) neurons expressed NOS immunoreactivity. Measurement in semithin sections of the size of the three neuronal populations found in PAG-dl, showed that Cal(IP) neurons had a cross-sectional area of 94.7 μm², whereas Nadph+ neurons and double-labeled neurons were slightly smaller, having a cross-sectional area of 90.5 and 91.4 μm², respectively. On electron microscopy, Cal(IP) axon terminals formed either symmetric or asymmetric synapses; although the latter synapses were more numerous, both types contacted preferentially Cal(IP) dendrites. These experiments suggest that PAG-dl is characterized by a high degree of heterogeneity.
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Affiliation(s)
- Paolp Barbaresi
- Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Marche Polytechnic University, I-60020 Ancona, Italy.
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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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Amaral VCS, Santos Gomes K, Nunes-de-Souza RL. Increased corticosterone levels in mice subjected to the rat exposure test. Horm Behav 2010; 57:128-33. [PMID: 19804780 DOI: 10.1016/j.yhbeh.2009.09.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 09/24/2009] [Accepted: 09/27/2009] [Indexed: 10/20/2022]
Abstract
In recent years, there has been a notable interest in studying prey-predator relationships to develop rodent-based models for the neurobehavioral aspects of stress and emotion. However, despite the growing use of transgenic mice and results showing important differences in the behavioral responses of rats and mice, little research has been conducted regarding the responses of mice to predators. The rat exposure test (RET), a recently developed and behaviorally validated prey-predator (mouse-rat)-based model, has proven to be a useful tool in evaluating the defensive responses of mice facing rats. To further validate the RET, we investigated the endocrine and behavioral responses of mice exposed to this apparatus. We first constructed a plasma corticosterone secretion curve in mice exposed to a rat or to an empty cage (control). Rat-exposed mice showed a pronounced rise in corticosterone levels that peaked 15 min from the beginning of the predator exposure. The corticosterone levels and behavioral responses of mice exposed to a rat or to a toy in the RET apparatus were then measured. We observed high plasma corticosterone levels along with clear avoidance behaviors represented by decreases in tunnel and surface area exploration and increases in risk assessment behaviors and freezing. This strongly suggests that the test elicits a repertoire of behavioral responses compatible with an aversion state and indicates that it is a promising model for the evaluation of prey-predator interactions. However, more physiological, neurochemical, and pharmacological studies are needed to further validate the test.
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