RESUMO
Pain is associated with negative emotions such as anxiety, but the underlying neurocircuitry and modulators of the association of pain and anxiety remain unclear. The neuropeptide cholecystokinin (CCK) has both pronociceptive and anxiogenic properties, so we explored the role of CCK in anxiety and nociception in the central amygdala (CeA), a key area in control of emotions and descending pain pathways. Local infusion of CCK into the CeA of control rats increased anxiety, as measured in the light-dark box test, but had no effect on mechanical sensitivity. By contrast, intra-CeA CCK infusion 4 days after Complete Freund's Adjuvant (CFA) injection into the hindpaw resulted in analgesia, but also in loss of its anxiogenic capacity. Inflammatory conditions induced changes in the CeA CCK signaling system with an increase of CCK immunoreactivity and a decrease in CCK1, but not CCK2, receptor mRNA. In CFA rats, patch-clamp experiments revealed that CCK infusion increased CeA neuron excitability. It also partially blocked the discharge of wide dynamic range neurons in the dorsal spinal cord. These effects of CCK on CeA and spinal neurons in CFA rats were mimicked by the specific CCK2 receptor agonist, gastrin. This analgesic effect was likely mediated by identified CeA neurons projecting to the periaqueductal gray matter that express CCK receptors. Together, our data demonstrate that intra-CeA CCK infusion activated a descending CCK2 receptor-dependent pathway that inhibited spinal neuron discharge. Thus, persistent pain induces a functional switch to a newly identified analgesic capacity of CCK in the amygdala, indicating central emotion-related circuit controls pain transmission in spinal cord.
Assuntos
Tonsila do Cerebelo/metabolismo , Colecistocinina/metabolismo , Dor/patologia , Receptor de Colecistocinina B/metabolismo , Transdução de Sinais/fisiologia , Tonsila do Cerebelo/patologia , Animais , Adaptação à Escuridão/efeitos dos fármacos , Modelos Animais de Doenças , Comportamento Exploratório/efeitos dos fármacos , Adjuvante de Freund/toxicidade , Gastrinas/uso terapêutico , Glutamato Descarboxilase/metabolismo , Inflamação/induzido quimicamente , Inflamação/complicações , Masculino , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Nociceptividade/efeitos dos fármacos , Dor/etiologia , Limiar da Dor/efeitos dos fármacos , Substância Cinzenta Periaquedutal/efeitos dos fármacos , Substância Cinzenta Periaquedutal/fisiologia , Ratos , Ratos Sprague-Dawley , Receptor de Colecistocinina B/agonistas , Receptor de Colecistocinina B/antagonistas & inibidores , Receptor de Colecistocinina B/genética , Transdução de Sinais/efeitos dos fármacos , Sincalida/uso terapêutico , Tetragastrina/análogos & derivados , Tetragastrina/uso terapêuticoRESUMO
C-low-threshold mechanoreceptors (C-LTMRs) are sensory neurons that, beyond conveying pleasant touch, modulate nociceptive transmission within the spinal cord. However, pain alleviation by C-LTMRs remains poorly understood. Here, we show that the C-LTMR-derived TAFA4 chemokine induces a reinforcement of inhibitory synaptic transmission within spinal networks, which consequently depresses local excitatory synapses and impairs synaptic transmission from high-threshold C-fibers. In animals with inflammation induced by Freund's complete adjuvant, TAFA4 decreases the noxious stimulus-induced neuronal responses recorded in vivo and alleviates mechanical pain. Both effects are blocked by antagonists of GABAergic transmission. Furthermore, TAFA4 promotes microglial retraction in inflammation and increases the number of inhibitory synapses on lamina IIi somata. Altogether, these results demonstrate GABAergic interneurons to be the first integration relay for C-LTMRs and highlight a tight interplay between sensory neurons, microglial cells, and spinal interneurons, which fine-tunes inhibitory activity and nociceptive transmission in pathological conditions.
Assuntos
Citocinas/farmacologia , Neurônios GABAérgicos/efeitos dos fármacos , Hiperalgesia/tratamento farmacológico , Animais , Neurônios GABAérgicos/patologia , Hiperalgesia/patologia , Camundongos , Camundongos Endogâmicos C57BL , Microglia/efeitos dos fármacos , Microglia/patologia , Nociceptividade/efeitos dos fármacos , Nociceptividade/fisiologia , Técnicas de Patch-Clamp , Corno Dorsal da Medula Espinal/efeitos dos fármacos , Corno Dorsal da Medula Espinal/patologia , Transmissão SinápticaRESUMO
L-type voltage-gated calcium channels are ubiquitous channels in the CNS. L-type calcium channels (LTCs) are mostly post-synaptic channels regulating neuronal firing and gene expression. They play a role in important physio-pathological processes such as learning and memory, Parkinson's disease, autism and, as recognized more recently, in the pathophysiology of pain processes. Classically, the fundamental role of these channels in cardiovascular functions has limited the use of classical molecules to treat LTC-dependent disorders. However, when applied locally in the dorsal horn of the spinal cord, the three families of LTC pharmacological blockers - dihydropyridines (nifedipine), phenylalkylamines (verapamil) and benzothiazepines (diltiazem) - proved effective in altering short-term sensitization to pain, inflammation-induced hyperexcitability and neuropathy-induced allodynia. Two subtypes of LTCs, Cav 1.2 and Cav 1.3, are expressed in the dorsal horn of the spinal cord, where Cav 1.2 channels are localized mostly in the soma and proximal dendritic shafts, and Cav 1.3 channels are more distally located in the somato-dendritic compartment. Together with their different kinetics and pharmacological properties, this spatial distribution contributes to their separate roles in shaping short- and long-term sensitization to pain. Cav 1.3 channels sustain the expression of plateau potentials, an input/output amplification phenomenon that contributes to short-term sensitization to pain such as prolonged after-discharges, dynamic receptive fields and windup. The Cav 1.2 channels support calcium influx that is crucial for the excitation-transcription coupling underlying nerve injury-induced dorsal horn hyperexcitability. These subtype-specific cellular mechanisms may have different consequences in the development and/or the maintenance of pathological pain. Recent progress in developing more specific compounds for each subunit will offer new opportunities to modulate LTCs for the treatment of pathological pain with reduced side-effects. LINKED ARTICLES: This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.
Assuntos
Canais de Cálcio Tipo L/metabolismo , Sinalização do Cálcio , Cálcio/metabolismo , Nociceptividade , Medula Espinal/fisiopatologia , Animais , Humanos , Medula Espinal/metabolismoRESUMO
Abstract: The dorsal horn of the spinal cord is a crucial site for pain transmission and modulation. Dorsal horn neurons of the spinal cord express group I metabotropic glutamate receptors (group I mGluRs) that exert a complex role in nociceptive transmission. In particular, group I mGluRs promote the activation of L-type calcium channels, voltage-gated channels involved in short- and long-term sensitization to pain. In this study, we analyzed the role of group I mGluRs in spinal nociceptive transmission and the possible cooperation between these receptors and L-type calcium channels in the pathophysiology of pain transmission in the dorsal horn of the spinal cord. We demonstrate that the activation of group I mGluRs induces allodynia and L-type calcium channel-dependent increase in nociceptive field potentials following sciatic nerve stimulation. Surprisingly, in a model of persistent inflammation induced by complete Freund's adjuvant, the activation of group I mGluRs induced an analgesia and a decrease in nociceptive field potentials. Among the group I mGluRs, mGluR1 promotes the activation of L-type calcium channels and increased nociceptive transmission while mGluR5 induces the opposite through the inhibitory network. These results suggest a functional switch exists in pathological conditions that can change the action of group I mGluR agonists into possible analgesic molecules, thereby suggesting new therapeutic perspectives to treat persistent pain in inflammatory settings.
Assuntos
Hiperalgesia/fisiopatologia , Inflamação/metabolismo , Plasticidade Neuronal/fisiologia , Receptores de Glutamato Metabotrópico/metabolismo , Animais , Masculino , Células do Corno Posterior/metabolismo , Ratos Sprague-Dawley , Receptores de Glutamato Metabotrópico/análise , Medula Espinal/fisiologia , Sinapses/metabolismoRESUMO
Strong breakthrough pain is one of the most disabling symptoms of cancer since it affects up to 90% of cancer patients and is often refractory to treatments. Alteration in gene expression is a known mechanism of cancer pain in which microRNAs (miRNAs), a class of non-coding regulatory RNAs, play a crucial role. Here, in a mouse model of cancer pain, we show that miR-124 is down-regulated in the spinal cord, the first relay of the pain signal to the brain. Using in vitro and in vivo approaches, we demonstrate that miR-124 is an endogenous and specific inhibitor of synaptopodin (Synpo), a key protein for synaptic transmission. In addition, we demonstrate that Synpo is a key component of the nociceptive pathways. Interestingly, miR-124 was down-regulated in the spinal cord in cancer pain conditions, leading to an up-regulation of Synpo. Furthermore, intrathecal injections of miR-124 mimics in cancerous mice normalized Synpo expression and completely alleviated cancer pain in the early phase of the cancer. Finally, miR-124 was also down-regulated in the cerebrospinal fluid of cancer patients who developed pain, suggesting that miR-124 could be an efficient analgesic drug to treat cancer pain patients.
Assuntos
Neoplasias Ósseas/fisiopatologia , Dor do Câncer/metabolismo , MicroRNAs/genética , Nociceptividade , Medula Espinal/metabolismo , Animais , Neoplasias Ósseas/complicações , Dor do Câncer/etiologia , Humanos , Masculino , Camundongos , MicroRNAs/metabolismo , Proteínas dos Microfilamentos/genética , Proteínas dos Microfilamentos/metabolismoRESUMO
KEY POINTS: L-type calcium channels in the CNS exist as two subunit forming channels, Cav1.2 and Cav1.3, which are involved in short- and long-term plasticity. We demonstrate that Cav1.3 but not Cav1.2 is essential for wind-up. These results identify Cav1.3 as a key conductance responsible for short-term sensitization in physiological pain transmission. We confirm the role of Cav1.2 in a model of long-term plasticity associated with neuropathic pain. Up-regulation of Cav1.2 and down-regultation of Cav1.3 in neuropathic pain underlies the switch from physiology to pathology. Finally, the results of the present study reveal that therapeutic targeting molecular pathways involved in wind-up may be not relevant in the treatment of neuropathy. ABSTRACT: Short-term central sensitization to pain temporarily increases the responsiveness of nociceptive pathways after peripheral injury. In dorsal horn neurons (DHNs), short-term sensitization can be monitored through the study of wind-up. Wind-up, a progressive increase in DHNs response following repetitive peripheral stimulations, depends on the post-synaptic L-type calcium channels. In the dorsal horn of the spinal cord, two L-type calcium channels are present, Cav1.2 and Cav1.3, each displaying specific kinetics and spatial distribution. In the present study, we used a mathematical model of DHNs in which we integrated the specific patterns of expression of each Cav subunits. This mathematical approach reveals that Cav1.3 is necessary for the onset of wind-up, whereas Cav1.2 is not and that synaptically triggered wind-up requires NMDA receptor activation. We then switched to a biological preparation in which we knocked down Cav subunits and confirmed the prominent role of Cav1.3 in both naive and spinal nerve ligation model of neuropathy (SNL). Interestingly, although a clear mechanical allodynia dependent on Cav1.2 expression was observed after SNL, the amplitude of wind-up was decreased. These results were confirmed with our model when adapting Cav1.3 conductance to the changes observed after SNL. Finally, our mathematical approach predicts that, although wind-up amplitude is decreased in SNL, plateau potentials are not altered, suggesting that plateau and wind-up are not fully equivalent. Wind-up and long-term hyperexcitability of DHNs are differentially controlled by Cav1.2 and Cav1.3, therefore confirming that short- and long-term sensitization are two different phenomena triggered by distinct mechanisms.
Assuntos
Canais de Cálcio Tipo L/metabolismo , Canais de Cálcio/metabolismo , Neuralgia/metabolismo , Potenciais de Ação/fisiologia , Animais , Hiperalgesia/metabolismo , Hiperalgesia/fisiopatologia , Masculino , Neuralgia/fisiopatologia , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/metabolismo , Medula Espinal/metabolismo , Medula Espinal/fisiopatologia , Corno Dorsal da Medula Espinal/metabolismo , Corno Dorsal da Medula Espinal/fisiopatologia , Nervos Espinhais/metabolismo , Nervos Espinhais/fisiopatologia , Sinapses/metabolismoRESUMO
In the spinal nerve ligation (SNL) model of neuropathic pain, synaptic plasticity shifts the excitation/inhibition balance toward excitation in the spinal dorsal horn. We investigated the deregulation of the synaptogenic neuroligin (NL) molecules, whose NL1 and NL2 isoforms are primarily encountered at excitatory and inhibitory synapses, respectively. In the dorsal horn of SNL rats, NL2 was overexpressed whereas NL1 remained unchanged. In control animals, intrathecal injections of small interfering RNA (siRNA) targeting NL2 increased mechanical sensitivity, which confirmed the association of NL2 with inhibition. By contrast, siRNA application produced antinociceptive effects in SNL rats. Regarding NL partners, expression of the excitatory postsynaptic scaffolding protein PSD95 unexpectedly covaried with NL2 overexpression, and NL2/PSD95 protein interaction and colocalization increased. Expression of the inhibitory scaffolding protein gephyrin remained unchanged, indicating a partial change in NL2 postsynaptic partners in SNL rats. This phenomenon appears to be specific to the NL2(-) isoform. Our data showed unexpected upregulation and pronociceptive effects of the "inhibitory" NL2 in neuropathic pain, suggesting a functional shift of NL2 from inhibition to excitation that changed the synaptic ratio toward higher excitation.
Assuntos
Moléculas de Adesão Celular Neuronais/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/fisiologia , Proteínas de Membrana/fisiologia , Proteínas do Tecido Nervoso/fisiologia , Neuralgia/fisiopatologia , Animais , Comportamento Animal/fisiologia , Western Blotting , Moléculas de Adesão Celular Neuronais/genética , Dor Crônica/fisiopatologia , Proteína 4 Homóloga a Disks-Large , Hiperalgesia/fisiopatologia , Imuno-Histoquímica , Imunoprecipitação , Hibridização In Situ , Peptídeos e Proteínas de Sinalização Intracelular/genética , Ligadura , Masculino , Proteínas de Membrana/genética , Fibras Nervosas Amielínicas/fisiologia , Proteínas do Tecido Nervoso/genética , Neuralgia/psicologia , Estimulação Física , Células do Corno Posterior/fisiologia , Interferência de RNA , RNA Interferente Pequeno/farmacologia , Ratos , Ratos Sprague-Dawley , Ratos Wistar , Reação em Cadeia da Polimerase em Tempo Real , Nervos Espinhais/fisiologiaRESUMO
The transfer of nociceptive information at the level of dorsal horn is subject to extensive processing by both local segmental and supraspinal mechanisms, including descending dopaminergic controls, originating from the hypothalamic A11 nucleus. The inhibitory role of dopamine on evoked pain via activation of D2-like receptors at the level of the dorsal horn is well established. Here, by use of behavioral, electrophysiological, and anatomical techniques, we examined within the trigeminal sensory complex, first, whether descending dopaminergic controls also modulate pain behavior after an inflammatory insult, and second, under which physiological conditions these descending dopaminergic controls are actually recruited. We show that D2 receptors are mostly located within superficial medullary dorsal horn where trigeminal nociceptive fibers abut. Activating these D2-like receptors inhibits, whereas blocking them enhances, both formalin- and capsaicin-evoked pain behavior and C-fiber-evoked action potential firing of trigeminal wide dynamic range (WDR) neurons. Moreover, windup and diffuse noxious inhibitory controls (DNIC), 2 dynamic properties of C-fiber-evoked firing of WDR neurons, are inhibited by activating and blocking, respectively, these D2-like receptors. Altogether, our results are consistent with a tonic inhibition of the trigeminal nociceptive input by descending dopaminergic controls via activation of D2-like receptors at the level of superficial medullary dorsal horn. Such dopamine-dependent tonic inhibition of nociceptive information can be dynamically modulated by pain. This suggests that dysregulation of descending dopaminergic controls should translate in patients into diffuse, cephalic, and extracephalic pain symptoms--spontaneous pain, decreased pain thresholds, deficient DNIC, or some combination of these.
Assuntos
Dopamina/metabolismo , Bulbo/patologia , Dor/patologia , Células do Corno Posterior/fisiopatologia , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Vias Aferentes/fisiologia , Análise de Variância , Animais , Capsaicina/efeitos adversos , Agonistas de Dopamina/farmacologia , Antagonistas de Dopamina/farmacologia , Estimulação Elétrica/métodos , Masculino , Microinjeções , Fibras Nervosas Mielinizadas/fisiologia , Fibras Nervosas Amielínicas/fisiologia , Dor/induzido quimicamente , Medição da Dor , Proteína Quinase C/metabolismo , Quimpirol/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de Dopamina D2/metabolismo , Medula Espinal/patologia , Sulpirida/farmacologiaRESUMO
BACKGROUND: Weight change during chemotherapy is reported to be associated with a worse prognosis in breast cancer patients, both with weight gain and weight loss. However, most studies were conducted prior to the common use of anthracycline-base chemotherapy and on North American populations with a mean BMI classified as overweight. Our study was aimed to evaluate the prognostic value of weight change during anthracycline-based chemotherapy on non metastatic breast cancer (European population) with a long term follow-up. METHODS: Patients included 111 women diagnosed with early stage breast cancer and locally advanced breast cancer who have been treated by anthracycline-based chemotherapy regimen between 1976 and 1989. The relative percent weight variation (WV) between baseline and postchemotherapy treatment was calculated and categorized into either weight change (WV > 5%) or stable (WV < 5%). The median follow-up was 20.4 years [19.4 - 27.6]. Cox proportional hazard models were used to evaluate any potential association of weight change and known prognostic factors with the time to recurrence and overall survival. RESULTS: Baseline BMI was 24.4 kg/m2 [17.1 - 40.5]. During chemotherapy treatment, 31% of patients presented a notable weight variation which was greater than 5% of their initial weight.In multivariate analyses, weight change (> 5%) was positively associated with an increased risk of both recurrence (RR 2.28; 95% CI: 1.29-4.03) and death (RR 2.11; 95% CI: 1.21-3.66). CONCLUSIONS: Our results suggest that weight change during breast-cancer chemotherapy treatment may be related to poorer prognosis with higher recurrence and higher mortality in comparison to women who maintained their weight.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Neoplasias da Mama/tratamento farmacológico , Aumento de Peso , Redução de Peso , Adulto , Antraciclinas/administração & dosagem , Índice de Massa Corporal , Neoplasias da Mama/mortalidade , Neoplasias da Mama/secundário , Distribuição de Qui-Quadrado , Intervalo Livre de Doença , Feminino , França , Humanos , Estimativa de Kaplan-Meier , Pessoa de Meia-Idade , Invasividade Neoplásica , Recidiva Local de Neoplasia , Estadiamento de Neoplasias , Modelos de Riscos Proporcionais , Estudos Retrospectivos , Medição de Risco , Fatores de Risco , Taxa de Sobrevida , Fatores de Tempo , Resultado do TratamentoRESUMO
Blood-borne hormones acting in the mediobasal hypothalamus, like those controlling food intake, require relatively direct access to target chemosensory neurons of the arcuate nucleus (ARC). An anatomical substrate for this is a permeable microvasculature with fenestrated endothelial cells in the ARC, a system that has awaited comprehensive documentation. Here, the immunofluorescent detection of endothelial fenestral diaphragms in the rat ARC allowed us to quantitate permeable microvessels throughout its rostrocaudal extent. We have determined that permeable microvessels are part of the subependymal plexus irrigating exclusively the ventromedial (vm) ARC from the subadjacent neuroendocrine median eminence. Unexpectedly, permeable microvessels were concentrated proximal to the pituitary stalk. This marked topography strongly supports the functional importance of retrograde blood flow from the pituitary to the vmARC, therefore making a functional relationship between peripheral long-loop, pituitary short-loop, and neuroendocrine ultra-short loop feedback, altogether converging for integration in the vmARC (formerly known as the hypophysiotrophic area), thereby so pivotal as a multicompetent brain endocrinostat.
Assuntos
Encéfalo/metabolismo , Sistema Endócrino/metabolismo , Hipotálamo/metabolismo , Microvasos/metabolismo , Sequência de Aminoácidos , Animais , Núcleo Arqueado do Hipotálamo/irrigação sanguínea , Núcleo Arqueado do Hipotálamo/metabolismo , Encéfalo/irrigação sanguínea , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Endotélio Vascular/metabolismo , Feminino , Hipotálamo/irrigação sanguínea , Immunoblotting , Imuno-Histoquímica , Hibridização In Situ , Masculino , Eminência Mediana/irrigação sanguínea , Eminência Mediana/metabolismo , Eminência Mediana/ultraestrutura , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Microscopia Eletrônica , Microvasos/fisiologia , Hipófise/irrigação sanguínea , Hipófise/metabolismo , Ratos , Ratos Wistar , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Diffuse noxious inhibitory controls (DNIC) are very powerful long-lasting descending inhibitory controls, which are pivotal in modulating the activity of spinal and trigeminal nociceptive neurons. The principal feature of DNIC is that they are subserved by a loop that involves supraspinal structures that have not yet been identified. Using behavioral, in vivo extracellular electrophysiological and anatomical approaches, we studied the neuronal network underlying DNIC. Using a new behavioral model of DNIC, in which facial grooming produced by formalin injection into the vibrissa pad is inhibited by a conditioning noxious stimulation, formalin injection into the hindpaw, we show that blockade of NK1 receptors in the lumbar spinal cord - by intrathecal administration of the NK1 receptor antagonist, RP67580 - largely attenuates DNIC-induced facial analgesia. In a second series of experiments, WDR neurons were recorded from the trigeminal subnucleus oralis and inhibited their C-fiber-evoked responses by the conditioning noxious heat stimulation of the hindpaw. We show that inactivating the lateral parabrachial area - by microinjecting the GABA(A) agonist, muscimol - strongly attenuates DNIC-induced inhibition of C-fiber-evoked responses. Finally, our neuroanatomical tracing study demonstrates that the descending pathway for DNIC does not involve direct descending projections from the PB area. We conclude that (1) lamina I/III spinoparabrachial neurons that express the NK1 receptor and (2) parabrachial neurons are involved in the ascending part of the loop underlying DNIC and that the descending pathway for DNIC might include indirect projections to the spinal or medullary dorsal horn.