RESUMO
Despite significant advances in the study of fear and fear memory formation, little is known about fear learning and expression in females. This omission has been proven surprising, as normal and pathological behaviors are highly influenced by ovarian hormones, particularly estradiol and progesterone. In the current study, we investigated the joint influence of serotonin (5-HT) neurotransmission and estrous cycle phases (low or high levels of estradiol and progesterone) on the expression of conditioned fear in a group of female rats that were previously divided according to their response to stressful stimuli into low or high anxiety-like subjects. The baseline amplitude of the unconditioned acoustic startle responses was high in high-anxiety female rats, with no effect on the estrous cycle observed. Data collected during the proestrus-estrus phase revealed that low-anxiety rats had startle amplitudes similar to those of high-anxiety rats. It is supposed that high-anxiety female rats benefit from increased estradiol and progesterone levels to achieve comparable potentiated startle amplitudes. In contrast, female rats experienced a significant decrease in hormone levels during the Diestrus phase. This decrease is believed to play a role in preventing them from displaying a heightened startle response when faced with strongly aversive stimuli. Data collected after 5-HT and 8-OH-DPAT were administered into the basolateral nuclei and dorsal periaqueductal gray suggest that 5-HT neurotransmission works with progesterone and estrogen to reduce startle potentiation, most likely by activating the serotonin-1A receptor subtype.
Assuntos
Complexo Nuclear Basolateral da Amígdala , Estradiol , Medo , Substância Cinzenta Periaquedutal , Progesterona , Receptor 5-HT1A de Serotonina , Reflexo de Sobressalto , Animais , Feminino , Ratos , Ansiedade/metabolismo , Ansiedade/fisiopatologia , Complexo Nuclear Basolateral da Amígdala/metabolismo , Complexo Nuclear Basolateral da Amígdala/efeitos dos fármacos , Condicionamento Clássico/fisiologia , Condicionamento Clássico/efeitos dos fármacos , Estradiol/farmacologia , Estradiol/metabolismo , Ciclo Estral/fisiologia , Medo/fisiologia , Medo/efeitos dos fármacos , Substância Cinzenta Periaquedutal/metabolismo , Substância Cinzenta Periaquedutal/efeitos dos fármacos , Progesterona/farmacologia , Progesterona/metabolismo , Ratos Wistar , Receptor 5-HT1A de Serotonina/metabolismo , Reflexo de Sobressalto/fisiologia , Reflexo de Sobressalto/efeitos dos fármacos , Serotonina/metabolismoRESUMO
RATIONALE: Muscarinic receptor activity in the basolateral amygdala (BLA) is known to be involved in plasticity mechanisms that underlie emotional learning. The BLA is involved in the Attenuation of Neophobia, an incidental taste learning task in which a novel taste becomes familiar and recognized as safe. OBJECTIVE: Here we assessed the role of muscarinic receptor activity in the BLA in incidental taste learning. METHODS: Young adult male Wistar rats were bilaterally implanted with cannulas aimed at BLA. After recovery, rats were randomly assigned to either vehicle or muscarinic antagonist group, for each experiment. We tested the effect of specific and non-specific muscarinic antagonists administered either 1) 20 min before novel taste presentation; 2) immediately after novel taste presentation; 3) immediately after retrieval (the second taste presentation on Day 5 -S2-) or immediately after the fifth taste presentation on Day 8 (S5). RESULTS: Non-specific muscarinic receptor antagonist scopolamine infused prior to novel taste, while not affecting novel taste preference, abolished AN, i.e., the increased preference observed in control animals on the second presentation. When administered after taste consumption, intra-BLA scopolamine not only prevented AN but caused a steep decrease in the taste preference on the second presentation. This scopolamine-induced taste avoidance was not dependent on taste novelty, nor did it generalize to another novel taste. Targeting putative postsynaptic muscarinic receptors with specific M1 or M3 antagonists appeared to produce a partial taste avoidance, while M2 antagonism had no effect. CONCLUSION: These data suggest that if a salient gustatory experience is followed by muscarinic receptors antagonism in the BLA, it will be strongly and persistently avoided in the future. The study also shows that scopolamine is not just an amnesic drug, and its cognitive effects may be highly dependent on the task and the structure involved.
Assuntos
Aprendizagem da Esquiva , Complexo Nuclear Basolateral da Amígdala , Antagonistas Muscarínicos , Ratos Wistar , Sacarina , Escopolamina , Paladar , Animais , Escopolamina/farmacologia , Escopolamina/administração & dosagem , Masculino , Antagonistas Muscarínicos/farmacologia , Antagonistas Muscarínicos/administração & dosagem , Complexo Nuclear Basolateral da Amígdala/efeitos dos fármacos , Complexo Nuclear Basolateral da Amígdala/metabolismo , Aprendizagem da Esquiva/efeitos dos fármacos , Ratos , Sacarina/administração & dosagem , Paladar/efeitos dos fármacos , Receptores Muscarínicos/metabolismoRESUMO
Growing evidence indicates a critical role of astrocytes in learning and memory. However, little is known about the role of basolateral amygdala complex (BLA-C) astrocytes in contextual fear conditioning (CFC), a paradigm relevant to understand and generate treatments for fear- and anxiety-related disorders. To get insights on the involvement of BLA-C astrocytes in fear memory, fluorocitrate (FLC), a reversible astroglial metabolic inhibitor, was applied at critical moments of the memory processing in order to target the acquisition, consolidation, retrieval and reconsolidation process of the fear memory. Adult Wistar male rats were bilaterally cannulated in BLA-C. Ten days later they were infused with different doses of FLC (0.5 or 1 nmol/0.5 µl) or saline before or after CFC and before or after retrieval. FLC impaired fear memory expression when administered before and shortly after CFC, but not one hour later. Infusion of FLC prior and after retrieval did not affect the memory. Our findings suggest that BLA-C astrocytes are critically involved in the acquisition/early consolidation of fear memory but not in the retrieval and reconsolidation. Furthermore, the extinction process was presumably not affected (considering that peri-retrieval administration could also affect this process).
Assuntos
Astrócitos , Complexo Nuclear Basolateral da Amígdala , Medo , Memória , Ratos Wistar , Animais , Medo/fisiologia , Medo/efeitos dos fármacos , Astrócitos/efeitos dos fármacos , Astrócitos/fisiologia , Masculino , Complexo Nuclear Basolateral da Amígdala/efeitos dos fármacos , Complexo Nuclear Basolateral da Amígdala/fisiologia , Ratos , Memória/fisiologia , Memória/efeitos dos fármacos , Citratos/farmacologia , Condicionamento Clássico/efeitos dos fármacos , Condicionamento Clássico/fisiologia , Consolidação da Memória/fisiologia , Consolidação da Memória/efeitos dos fármacos , Tonsila do Cerebelo/efeitos dos fármacos , Tonsila do Cerebelo/fisiologia , Extinção Psicológica/efeitos dos fármacos , Extinção Psicológica/fisiologiaRESUMO
Memories are stored in engram cells, which are necessary and sufficient for memory recall. Recalling a memory might undergo reconsolidation or extinction. It has been suggested that the original memory engram is reactivated during reconsolidation so that memory can be updated. Conversely, during extinction training, a new memory is formed that suppresses the original engram. Nonetheless, it is unknown whether extinction creates a new engram or modifies the original fear engram. In this study, we utilized the Daun02 procedure, which uses c-Fos-lacZ rats to induce apoptosis of strongly activated neurons and examine whether a new memory trace emerges as a result of a short or long reactivation, or if these processes rely on modifications within the original engram located in the basolateral amygdala (BLA) and infralimbic (IL) cortex. By eliminating neurons activated during consolidation and reactivation, we observed significant impacts on fear memory, highlighting the importance of the BLA engram in these processes. Although we were unable to show any impact when removing the neurons activated after the test of a previously extinguished memory in the BLA, disrupting the IL extinction engram reactivated the aversive memory that was suppressed by the extinction memory. Thus, we demonstrated that the IL cortex plays a crucial role in the network involved in extinction, and disrupting this specific node alone is sufficient to impair extinction behavior. Additionally, our findings indicate that extinction memories rely on the formation of a new memory, supporting the theory that extinction memories rely on the formation of a new memory, whereas the reconsolidation process reactivates the same original memory trace.
Assuntos
Complexo Nuclear Basolateral da Amígdala , Extinção Psicológica , Medo , Neurônios , Animais , Extinção Psicológica/fisiologia , Medo/fisiologia , Masculino , Neurônios/fisiologia , Complexo Nuclear Basolateral da Amígdala/fisiologia , Ratos , Memória/fisiologia , Ratos Transgênicos , Proteínas Proto-Oncogênicas c-fos/metabolismo , Consolidação da Memória/fisiologiaRESUMO
Dysfunction of the corticolimbic system, particularly at the dendritic spine level, is a recognized core mechanism in neurodevelopmental disorders such as schizophrenia. Neonatal ventral hippocampus lesion (NVHL) in Sprague-Dawley rats induces both a schizophrenia-related behavioral phenotype and dendritic spine pathology (reduced total number and mature spines) in corticolimbic areas, which is mitigated by antipsychotics. However, there is limited information on the impact of rat strain on NVHL outcomes and antipsychotic effects. We compared the behavioral performance in the open field, novel object recognition (NORT), and social interaction tests, as well as structural neuroplasticity with the Golgi-Cox stain in Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) male rats with and without NVHL. Additionally, we explored the effect of the atypical antipsychotic risperidone (RISP). WKY rats with NVHL displayed motor hyperactivity without impairments in memory and social behavior, accompanied by dendritic spine pathology in the neurons of the prefrontal cortex (PFC) layer 3 and basolateral amygdala. RISP treatment reduced motor activity and had subtle and selective effects on the neuroplasticity alterations. In SH rats, NVHL increased the time spent in the border area during the open field test, impaired the short-term performance in NORT, and reduced social interaction time, deficits that were corrected after RISP administration. The NVHL caused dendritic spine pathology in the PFC layers 3 and 5 of SH rats, which RISP treatment ameliorated. Our results support the utility of the NVHL model for exploring neuroplasticity mechanisms in schizophrenia and understanding pharmacotherapy.
Assuntos
Antipsicóticos , Hipocampo , Animais , Ratos , Masculino , Ratos Endogâmicos SHR , Ratos Sprague-Dawley , Ratos Endogâmicos WKY , Animais Recém-Nascidos , Córtex Pré-Frontal , Risperidona , Antipsicóticos/farmacologia , Modelos Animais de DoençasRESUMO
Environmental enrichment (EE) has been demonstrated to have a beneficial effect on different functions of the central nervous system in several mammal species, being used to improve behavior and cell damage in various neurological and psychiatric diseases. However, little has been investigated on the effect of EE in healthy animals, particularly regarding its impact on memory persistence and the brain structures involved. Therefore, here we verified in male Wistar rats that contextual fear conditioning (CFC) memory persistence, tested 28 days after the CFC training session, was facilitated by 5 weeks of exposure to EE, with no effect in groups tested 7 or 14 days after CFC training. However, a two-week exposure to EE did not affect memory persistence. Moreover, we investigated the role of specific brain regions in mediating the effect of EE on memory persistence. We conducted inactivation experiments using the GABAergic agonist Muscimol to target the basolateral amygdala (BLA), medial prefrontal cortex (mPFC), and CA1 region of the hippocampus (CA1). Inactivation of the BLA immediately and 12 h after CFC training impaired the effect of EE on memory persistence. Similarly, inactivation of the CA1 region and mPFC 12 h after training, but not immediately, also impaired the effect of EE on memory persistence. These results have important scientific implications as they shed new light on the effect of an enriched environment on memory persistence and the brain structures involved, thereby helping elucidate how an environment rich in experiences can modify the persistence of learned information.
Assuntos
Tonsila do Cerebelo , Memória , Ratos , Animais , Masculino , Ratos Wistar , Aprendizagem/fisiologia , Encéfalo , Hipocampo/fisiologia , Córtex Pré-Frontal/fisiologia , MamíferosRESUMO
Ethanol is the most consumed substance of abuse in the world, and its misuse may lead to the development of alcohol use disorder (AUD). High relapse rates remain a relevant problem in the treatment of AUD. Exposure to environmental cues previously associated with ethanol intake could trigger ethanol-seeking behavior. However, the neural mechanisms involved in this phenomenon are not entirely clear. In this context, cortical projections to the basolateral amygdala (BLA) play a role in appetitive and aversive learned behaviors. Therefore, we aimed to evaluate the activation of the cortical projections from the prelimbic (PL), orbitofrontal (OFC), and infralimbic (IL), to the BLA in the context-induced reinstatement of ethanol-seeking. Male Long-Evans rats were trained to self-administer 10% ethanol in Context A. Subsequently, lever pressing in the presence of the discrete cue was extinguished in Context B. After nine extinction sessions, rats underwent intracranial surgery for the unilateral injection of red fluorescent retrograde tracer into the BLA. The context-induced reinstatement of ethanol-seeking was assessed by re-exposing the rats to Context A or B under extinction conditions. Finally, we combined retrograde neuronal tracing with Fos to identify activated cortical inputs to BLA during the reinstatement of ethanol-seeking behavior. We found that PL, but not OFC or IL, retrogradely-labeled neurons from BLA presented increased Fos expression during the re-exposure to the ethanol-associated context, suggesting that PL projection to BLA is involved in the context-induced reinstatement of ethanol-seeking behavior.
Assuntos
Alcoolismo , Complexo Nuclear Basolateral da Amígdala , Ratos , Masculino , Animais , Etanol/farmacologia , Extinção Psicológica , Ratos Sprague-Dawley , Tonsila do Cerebelo/fisiologia , Ratos Long-Evans , Sinais (Psicologia) , AutoadministraçãoRESUMO
Growth factors, such as insulin-like growth factor 1 (IGF-1), among others are known for their critical involvement in learning and memory processes. IGF-1 regulates cognitive functions, synapse density, neurotransmission, and adult neurogenesis and induces structural and synaptic plasticity-specific changes. Although IGF-1 has been suggested to participate in different memory processes, its role in memories associated with negative emotional experiences still remains to be elucidated. The principal aim of the present study was to test whether IGF-1 overexpression using adenoviral vectors in basolateral amygdala (BLA) influences both the expression and formation of contextual fear memory, as well as the hippocampal structural plasticity associated with such memory trace. We found that IGF-1 overexpression promotes the formation and expression of a specific contextual fear memory trace, and such effect persisted at least 7 days after recall. Moreover, the overexpression of this growth factor in BLA upregulates the activation of the ERK/MAPK pathway in this brain structure. In addition, intra-BLA IGF-1 overexpression causes dorsal hippocampus (DH) structural plasticity modifications promoting changes in the proportion of mature dendritic spines in the CA1 region, after a weak conditioning protocol. The present findings contribute to the knowledge underlying BLA-DH trace memory of fear and reveal important new insights into the neurobiology and neurochemistry of fear acquisition modulated by IGF-1 overexpression. The understanding of how IGF-1 modulates the formation of a fear contextual trace may pave the way for the development of novel therapeutic strategies focused on fear, anxiety, and trauma-related disorders.
Assuntos
Complexo Nuclear Basolateral da Amígdala , Complexo Nuclear Basolateral da Amígdala/fisiologia , Medo/fisiologia , Hipocampo/fisiologia , Fator de Crescimento Insulin-Like I/genética , Fator de Crescimento Insulin-Like I/metabolismo , Memória/fisiologiaRESUMO
Morphine withdrawal can trigger disruptions in neuronal pathways involved in the modulation and expression of anxiety and fear-related behaviors, particularly those involved in associative learning. When it comes to contextual fear, specific subdivisions of the medial prefrontal cortex (mPFC) regulate the expression of defensive behaviors through projections to specific amygdala (AM) nuclei, such as the prelimbic cortex (PrL). The basolateral nucleus (BLA) of the AM has been shown to be involved in the modulation and expression of associative memories of fear, including those associated with opiate withdrawal-related aversive events. The purpose of this study is to determine the role of GABA mechanisms in the PrL and BLA in startle potentiation and freezing behavior caused by morphine-precipitated withdrawal. Our findings show that morphine withdrawal promotes the emergence of contextual conditioned fear in animals when they are exposed to the same environment where the withdrawal sessions were performed. This suggests that the neural circuits underlying the organism's response to conditioned stressors and the circuits modulating the negative affective states induced by drug withdrawal may overlap. The pharmacological manipulation of GABAergic neurotransmission in the PrL and BLA can reverse contextual fear in morphine-withdrawn rats, an effect that appears to be mediated, at least in part, by GABAA receptors.
Assuntos
Complexo Nuclear Basolateral da Amígdala , Tonsila do Cerebelo , Animais , Medo/fisiologia , Morfina/efeitos adversos , Córtex Pré-Frontal/fisiologia , Ratos , Receptores de GABA-A , Ácido gama-AminobutíricoRESUMO
The ability to retrieve contextual fear memories depends on the coordinated activation of a brain-wide circuitry. Transition from recent to remote memories seems to involve the reorganization of this circuitry, a process called systems consolidation that has been associated with time-dependent fear generalization. However, it is unknown whether emotional memories acquired under different stress levels can undergo different systems consolidation processes. Here, we explored the activation pattern and functional connectivity of key brain regions associated with contextual fear conditioning (CFC) retrieval after recent (2 days) or remote (28 days) memory tests performed in rats submitted to strong (1.0 mA footshock) or mild (0.3 mA footshock) training. We used brain tissue from Wistar rats from a previous study, where we observed that increasing training intensity promotes fear memory generalization over time, possibly due to an increase in corticosterone (CORT) levels during memory consolidation. Analysis of Fos expression across 8 regions of interest (ROIs) allowed us to identify coactivation between them at both timepoints following memory recall. Our results showed that strong CFC elicits higher Fos activation in the anterior insular and prelimbic cortices during remote retrieval, which was positively correlated with freezing along with the basolateral amygdala. Rats trained either with mild or strong CFC showed broad functional connectivity at the recent timepoint whereas only animals submitted to the strong CFC showed a widespread loss of coactivation during remote retrieval. Post-training plasma CORT levels are positively correlated with FOS expression during recent retrieval in strong CFC, but negatively correlated with FOS expression during remote retrieval in mild CFC. Our findings suggest that increasing training intensity results in differential processes of systems consolidation, possibly associated with increased post-training CORT release, and that strong CFC engages activity from the aIC, BLA and PrL - areas associated with the Salience Network in rats - during remote retrieval.
RESUMO
Astrocytes release gliotransmitters via connexin 43 (Cx43) hemichannels into neighboring synapses, which can modulate synaptic activity and are necessary for fear memory consolidation. However, the gliotransmitters released, and their mechanisms of action remain elusive. Here, we report that fear conditioning training elevated Cx43 hemichannel activity in astrocytes from the basolateral amygdala (BLA). The selective blockade of Cx43 hemichannels by microinfusion of TAT-Cx43L2 peptide into the BLA induced memory deficits 1 and 24 h after training, without affecting learning. The memory impairments were prevented by the co-injection of glutamate and D-serine, but not by the injection of either alone, suggesting a role for NMDA receptors (NMDAR). The incubation with TAT-Cx43L2 decreased NMDAR-mediated currents in BLA slices, effect that was also prevented by the addition of glutamate and D-serine. NMDARs in primary neuronal cultures were unaffected by TAT-Cx43L2, ruling out direct effects of the peptide on NMDARs. Finally, we show that D-serine permeates through purified Cx43 hemichannels reconstituted in liposomes. We propose that the release of glutamate and D-serine from astrocytes through Cx43 hemichannels is necessary for the activation of post-synaptic NMDARs during training, to allow for the formation of short-term and subsequent long-term memory, but not for learning per se.
Assuntos
Astrócitos/metabolismo , Complexo Nuclear Basolateral da Amígdala/metabolismo , Conexina 43/metabolismo , Medo/fisiologia , Memória de Curto Prazo/fisiologia , Neurotransmissores/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Animais , Ácido Glutâmico/metabolismo , Masculino , Neurônios/metabolismo , Ratos , Ratos Sprague-Dawley , Serina/metabolismoRESUMO
Reinforcement learning theories postulate that prediction error, i.e., a discrepancy between the actual and expected outcomes, drives reconsolidation and new learning, inducing an updating of the initial memory. Pavlovian studies have shown that prediction error detection is a fundamental mechanism in triggering amygdala-dependent memory updating, where the temporal relationship between stimuli plays a critical role. However, in contrast to the well-established findings in aversive situations (e.g., fear conditioning), only few studies exist on prediction error in appetitive operant conditioning, and even less with regard to the role of temporal parameters. To explore if temporal prediction error in an appetitive operant paradigm could generate an updating and consequent reconsolidation and/or new learning of temporal association, we ran four experiments in adult male rats. Experiment 1 verified whether an unexpected delay in the time of reward's availability (i.e., a negative temporal prediction error) in a single session produces an updating in long-term memory of temporal expectancy in an appetitive operant conditioning. Experiment 2 showed that negative prediction errors, either due to the temporal change or through reward omission, increased in the basolateral amygdala nucleus (BLA) the activation of a protein that is critical for memory formation. Experiment 3 revealed that the presence of a protein synthesis inhibitor (anisomycin) in the BLA during the session when the reward was delayed (Error session) affected the temporal updating. Finally, Experiment 4 showed that anisomycin, when infused immediately after the Error session, interfered with the long-term memory of the temporal updating. Together, our study demonstrated an involvement of BLA after a change in temporal and reward contingencies, and in the resulting updating in long-term memory in appetitive operant conditioning.
RESUMO
Synaptic plasticity is a key mechanism of neural plasticity involved in learning and memory. A reduced or impaired synaptic plasticity could lead to a deficient learning and memory. On the other hand, besides reducing hipocampal dependent learning and memory, fimbria-fornix lesion affects LTP. However, we have consistently shown that stimulation of the basolateral amygdala (BLA) 15 min after water maze training is able to improve spatial learning and memory in fimbria fornix lesioned rats while also inducing changes in the expression of plasticity-related genes expression in memory associated brain regions like the hippocampus and prefrontal cortex. In this study we test that hypothesis: whether BLA stimulation 15 min after water maze training can improve LTP in the hippocampus of fimbria-fornix lesioned rats. To address this question, we trained fimbria-fornix lesioned rats in water maze for four consecutive days, and the BLA was bilaterally stimulated 15 min after each training session.Our data show that trained fimbria-fornix lesioned rats develop a partially improved LTP in dentated gyrus compared with the non-trained fimbria-fornix lesioned rats. In contrast, dentated gyrus LTP in trained and BLA stimulated fimbria-fornix lesioned rats improved significantly compared to the trained fimbria-fornix lesioned rats, but was not different from that shown by healthy animals. BLA stimulation in non-trained FF lesioned rats did not improve LTP; instead produces a transient synaptic depression. Restoration of the ability to develop LTP by the combination of training and BLA stimulation would be one of the mechanisms involved in ameliorating memory deficits in lesioned animals.
Assuntos
Complexo Nuclear Basolateral da Amígdala/fisiologia , Giro Denteado/fisiologia , Potenciação de Longa Duração/fisiologia , Aprendizagem em Labirinto/fisiologia , Aprendizagem Espacial/fisiologia , Memória Espacial/fisiologia , Animais , Fórnice/lesões , Masculino , Plasticidade Neuronal/fisiologia , Córtex Pré-Frontal/fisiologia , Ratos , Ratos WistarRESUMO
The incidence of chronic pain is high in the general population and it is closely related to anxiety disorders, which promote negative effects on the quality of life. The cannabinoid system has essential participation in the pain sensitivity circuit. In this perspective, cannabidiol (CBD) is considered a promising strategy for treating neuropathic pain. Our study aimed to evaluate the effects of sub-chronic systemic treatment with CBD (0.3, 3, 10, or 30 mg/kg, i.p.) in male in rats submitted to chronic constriction injury of the sciatic nerve (CCI) or not (SHAM) and assessed in nociceptive tests (von Frey, acetone, and hot plate, three days CBD's treatment) and in the open field test (OFT, two days CBD's treatment). We performed a screening immunoreactivity of CB1 and TRPV1 receptors in cortical and limbic regions tissues, which were collected after 1.5 h of behavioral tests on the 24th experimental day. This study presents a dose-response curve to understand better the effects of low doses (3 mg/kg) on CBD's antiallodynic and anxiolytic effects. Also, low doses of CBD were able to (1) reverse mechanical and thermal allodynia (cold) and hyperalgesia, (2) reverse anxious behaviors (reduction of the % of grooming and freezing time, and increase of the % of center time in the OFT) induced by chronic pain. The peripheral neuropathy promoted the increase in the expression of CB1 and TRPV1 receptors in the anterior cingulate cortex (ACC), anterior insular cortex (AIC), basolateral amygdala (BLA), dorsal hippocampus (DH), and ventral hippocampus (VH). CBD potentiated this effect in the ACC, AIC, BLA, DH, and VH regions. These results provide substantial evidence of the role of the ACC-AIC-BLA corticolimbic circuit, and BLA-VH for pain regulation. These results can be clinically relevant since they contribute to the evidence of CBD's beneficial effects on treating chronic pain and associated comorbidities such as anxiety.
Assuntos
Ansiedade/tratamento farmacológico , Canabidiol/uso terapêutico , Hiperalgesia/tratamento farmacológico , Neuralgia/tratamento farmacológico , Receptor CB1 de Canabinoide/efeitos dos fármacos , Canais de Cátion TRPV/efeitos dos fármacos , Animais , Ansiedade/psicologia , Córtex Cerebral/metabolismo , Hipocampo/metabolismo , Temperatura Alta , Sistema Límbico/efeitos dos fármacos , Masculino , Rede Nervosa/efeitos dos fármacos , Neuralgia/metabolismo , Neuralgia/psicologia , Medição da Dor/efeitos dos fármacos , Estimulação Física , Ratos , Ratos Wistar , Ciática/tratamento farmacológicoRESUMO
Typical amnestic treatments are ineffective when administered to subjects trained in aversively-motivated tasks using relatively high foot-shock intensities. This effect has been found when treatments that disrupt neuronal activity are administered to different regions of the brain, including the amygdala. However, the molecular mechanisms induced by this intense training are unknown. We made a detailed mapping of c-Fos-expressing neurons in four regions of the amygdala after moderate and intense one-trial inhibitory avoidance training. Rats were sacrificed 90â¯min after training or after appropriate control procedures, and their brains were prepared for immunohistochemical c-Fos protein detection in the central, lateral, and in the anterior and posterior parts of the basolateral amygdaloid nucleus. We found a high percentage of neurons expressing c-Fos in the anterior part of the basolateral nucleus after moderate training, and this percentage increased further after intense training. Moderate and intense training did not induce changes in c-Fos expression in the other explored amygdaloid regions. These results show that inhibitory avoidance training produces a localized expression of c-Fos in the basolateral anterior nucleus of the amygdala, which is dependent upon the intensity of training, and indicate that synaptic plastic changes in this region may be required for the formation of memory of moderate and intense aversive learning.
Assuntos
Aprendizagem da Esquiva/fisiologia , Complexo Nuclear Basolateral da Amígdala/fisiologia , Neurônios/fisiologia , Animais , Complexo Nuclear Basolateral da Amígdala/metabolismo , Extinção Psicológica , Inibição Psicológica , Masculino , Memória/fisiologia , Neurônios/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , RatosRESUMO
The destabilization/reconsolidation process can be triggered by memory recall, allowing consolidated memories to be modified. We have previously reported that stress prior to fear conditioning induces memories that exhibit resistance to the engagement of some molecular events associated with the destabilization/reconsolidation process. Here, we evaluated whether stress could affect the expression of Lys-48 polyubiquitinated proteins within the basolateral amygdala complex, a phenomenon crucially linked to memory destabilization. As expected, a post-recall increase of Lys-48 polyubiquitinated proteins in control animals was observed; however, this phenomenon was prevented by stress exposure before fear conditioning. On the other hand, pre-recall administration of D-cycloserine -a positive modulator of NMDA sites capable of reverting memory resistance to pharmacological interference-, facilitated the increase of Lys-48 polyubiquitinated proteins in stressed animals. In conclusion, the protein polyubiquitination-dependent destabilization is impaired after the recall of stress-induced resistant memories, with D-cycloserine restoring such molecular event. Hence, the present report contributes to further characterize the neurobiological events associated with stress-induced memory resistance as well as to corroborate the connection between glutamatergic signaling, protein degradation and memory destabilization in stress-induced resistant memories.
Assuntos
Complexo Nuclear Basolateral da Amígdala/metabolismo , Condicionamento Clássico/fisiologia , Medo , Consolidação da Memória/fisiologia , Rememoração Mental/fisiologia , Estresse Psicológico/metabolismo , Animais , Complexo Nuclear Basolateral da Amígdala/efeitos dos fármacos , Condicionamento Clássico/efeitos dos fármacos , Ciclosserina/farmacologia , Masculino , Memória/efeitos dos fármacos , Memória/fisiologia , Consolidação da Memória/efeitos dos fármacos , Rememoração Mental/efeitos dos fármacos , Poliubiquitina/metabolismo , Ratos , Ubiquitinação/efeitos dos fármacosRESUMO
It has been shown that fear conditioning improves the steady-state evoked potentials driven by a long lasting amplitude modulated tone in the inferior colliculus. In this work we tested the hypothesis that the amygdala modulates this effect, since it plays a crucial role in assessing the biological relevance of environmental stimuli. We inhibited the basolateral nucleus of the amygdala of rats by injecting a GABAa receptor agonist (muscimol) before the recall test session of an auditory fear conditioning paradigm and recorded the evoked activity in the central nucleus of the inferior colliculus. According to our results, the treatment with muscimol decreased the expression of freezing behavior during the recall test session, but did not impair the entrainment of the evoked activity in the inferior colliculus induced by fear conditioning. We repeated the injection protocol with another group of rats but without pairing the tone to an aversive stimulus and observed that the inhibition of the basolateral amygdala enhances the stimulus-driven activity in the inferior colliculus regardless of the conditioning task. Our findings suggest that the basolateral amygdala exerts a tonic modulation over the encoding of sensory information at the early stages of the sensory pathway.
Assuntos
Tonsila do Cerebelo/fisiologia , Condicionamento Clássico/fisiologia , Potenciais Evocados/fisiologia , Medo/fisiologia , Colículos Inferiores/fisiologia , Estimulação Acústica , Tonsila do Cerebelo/efeitos dos fármacos , Animais , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Condicionamento Clássico/efeitos dos fármacos , Potenciais Evocados/efeitos dos fármacos , Agonistas de Receptores de GABA-A/farmacologia , Colículos Inferiores/efeitos dos fármacos , Masculino , Muscimol/farmacologia , Ratos , Ratos WistarRESUMO
Though sex differences in chronic pain have been consistently described in the literature, their underlying neural mechanisms are poorly understood. Previous work in humans has demonstrated that men and women differentially invoke distinct brain regions and circuits in coping with subjective pain unpleasantness. The goal of the present work was to elucidate the molecular mechanisms in the basolateral nucleus of the amygdala (BLA) that modulate hyperalgesic priming, a pain plasticity model, in males and females. We used plantar incision as the first, priming stimulus and prostaglandin E2 (PGE2) as the second stimulus. We sought to assess whether hyperalgesic priming can be prevented or reversed by pharmacologically manipulating molecular targets in the BLA of male or female mice. We found that administering ZIP, a cell-permeable inhibitor of aPKC, into the BLA attenuated aspects of hyperalgesic priming induced by plantar incision in males and females. However, incision only upregulated PKCζ/PKMζ immunoreactivity in the BLA of male mice, and deficits in hyperalgesic priming were seen only when we restricted our analysis to male Prkcz-/- mice. On the other hand, intra-BLA microinjections of pep2m, a peptide that interferes with the trafficking and function of GluA2-containing AMPA receptors, a downstream target of aPKC, reduced mechanical hypersensitivity after plantar incision and disrupted the development of hyperalgesic priming in both male and female mice. In addition, pep2m treatment reduced facial grimacing and restored aberrant behavioral responses in the sucrose splash test in male and female primed mice. Immunofluorescence results demonstrated upregulation of GluA2 expression in the BLA of male and female primed mice, consistent with pep2m findings. We conclude that, in a model of incision-induced hyperalgesic priming, PKCζ/PKMζ in the BLA is critical for the development of hyperalgesic priming in males, while GluA2 in the BLA is crucial for the expression of both reflexive and affective pain-related behaviors in both male and female mice in this model. Our findings add to a growing body of evidence of sex differences in molecular pain mechanisms in the brain.
RESUMO
BACKGROUND: Stimulation of serotonergic neurons within the dorsal raphe dorsomedial subnucleus facilitates inhibitory avoidance acquisition in the elevated T-maze. It has been hypothesized that such anxiogenic effect is due to serotonin release in the basolateral nucleus of the amygdala, where facilitation of serotonin 2C receptor-mediated neurotransmission increases anxiety. Besides the dorsal raphe dorsomedial subnucleus, the dorsal raphe caudal subnucleus is recruited by anxiogenic stimulus/situations. However, the behavioral consequences of pharmacological manipulation of this subnucleus are still unknown. AIMS: Investigate whether blockade of serotonin 2C receptors in the basolateral nucleus of the amygdala counteracts the anxiogenic effect caused by the stimulation of dorsal raphe dorsomedial subnucleus serotonergic neurons. Evaluate the effects caused by the excitatory amino acid kainic acid or serotonin 1A receptor-modulating drugs in the dorsal raphe caudal subnucleus. METHODS: Male Wistar rats were tested in the elevated T-maze and light-dark transition tests after intra-basolateral nucleus of the amygdala injection of the serotonin 2C receptor antagonist SB-242084 (6-chloro-2,3-dihydro-5-methyl-N-[6-[(2-methyl-3-pyridinyl)oxy]-3-pyridinyl]-1H-indole-1-carboxyamide dihydrochloride) followed by intra-dorsal raphe dorsomedial subnucleus administration of the serotonin 1A receptor antagonist WAY-100635 (N-[2-[4-2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinil-cyclohexanecarboxamide maleate). In the dorsal raphe caudal subnucleus, animals were injected with kainic acid, WAY-100635 or the serotonin 1A receptor agonist 8-OH-DPAT ((±)-8-hydroxy-2-(di-n-propylamino) tetralin hydrobromide) and tested in the elevated T-maze. RESULTS: SB-242084 in the basolateral nucleus of the amygdala blocked the anxiogenic effect caused by the injection of WAY-100635 in the dorsal raphe dorsomedial subnucleus. Kainic acid in the dorsal raphe caudal subnucleus increased anxiety, but also impaired escape expression in the elevated T-maze. Neither WAY-100635 nor 8-OH-DPAT in the dorsal raphe caudal subnucleus affected rat's behavior in the elevated T-maze. CONCLUSION: Serotonin 2C receptors in the basolateral nucleus of the amygdala mediate the anxiogenic effect caused by the stimulation of serotonergic neurons in the dorsal raphe dorsomedial subnucleus. The dorsal raphe caudal subnucleus regulates anxiety- and panic-like behaviors, presumably by a serotonin 1A receptor-independent mechanism.
Assuntos
Ansiedade/induzido quimicamente , Complexo Nuclear Basolateral da Amígdala/efeitos dos fármacos , Núcleo Dorsal da Rafe/efeitos dos fármacos , Receptor 5-HT2C de Serotonina/efeitos dos fármacos , Serotonina/metabolismo , 8-Hidroxi-2-(di-n-propilamino)tetralina/farmacologia , Aminopiridinas/farmacologia , Animais , Ansiedade/psicologia , Estimulação Elétrica , Indóis/farmacologia , Ácido Caínico , Masculino , Piperazinas/farmacologia , Piridinas/farmacologia , Ratos , Ratos Wistar , Neurônios Serotoninérgicos/efeitos dos fármacos , Antagonistas da Serotonina/farmacologia , Agonistas do Receptor de Serotonina/farmacologiaRESUMO
BACKGROUND: Basolateral amygdalar projections to the prefrontal cortex play a key role in modulating behavioral responses to stress stimuli. Among the different neuromodulators known to impact basolateral amygdalar-prefrontal cortex transmission, the corticotrophin releasing factor (CRF) is of particular interest because of its role in modulating anxiety and stress-associated behaviors. While CRF type 1 receptor (CRFR1) has been involved in prefrontal cortex functioning, the participation of CRF type 2 receptor (CRFR2) in basolateral amygdalar-prefrontal cortex synaptic transmission remains unclear. METHODS: Immunofluorescence anatomical studies using rat prefrontal cortex synaptosomes devoid of postsynaptic elements were performed in rats with intra basolateral amygdalar injection of biotinylated dextran amine. In vivo microdialysis and local field potential recordings were used to measure glutamate extracellular levels and changes in long-term potentiation in prefrontal cortex induced by basolateral amygdalar stimulation in the absence or presence of CRF receptor antagonists. RESULTS: We found evidence for the presynaptic expression of CRFR2 protein and mRNA in prefrontal cortex synaptic terminals originated from basolateral amygdalar. By means of microdialysis and electrophysiological recordings in combination with an intra-prefrontal cortex infusion of the CRFR2 antagonist antisauvagine-30, we were able to determine that CRFR2 is functionally positioned to limit the strength of basolateral amygdalar transmission to the prefrontal cortex through presynaptic inhibition of glutamate release. CONCLUSIONS: Our study shows for the first time to our knowledge that CRFR2 is expressed in basolateral amygdalar afferents projecting to the prefrontal cortex and exerts an inhibitory control of prefrontal cortex responses to basolateral amygdalar inputs. Thus, changes in CRFR2 signaling are likely to disrupt the functional connectivity of the basolateral amygdalar-prefrontal cortex pathway and associated behavioral responses.