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1.
Nat Commun ; 10(1): 4253, 2019 09 18.
Artículo en Inglés | MEDLINE | ID: mdl-31534133

RESUMEN

Medication-overuse headaches (MOH) occur with both over-the-counter and pain-relief medicines, including paracetamol, opioids and combination analgesics. The mechanisms that lead to MOH are still uncertain. Here, we show that abnormal activation of Nav1.9 channels by Nitric Oxide (NO) is responsible for MOH induced by triptan migraine medicine. Deletion of the Scn11a gene in MOH mice abrogates NO-mediated symptoms, including cephalic and extracephalic allodynia, photophobia and phonophobia. NO strongly activates Nav1.9 in dural afferent neurons from MOH but not normal mice. Abnormal activation of Nav1.9 triggers CGRP secretion, causing artery dilatation and degranulation of mast cells. In turn, released mast cell mediators potentiates Nav1.9 in meningeal nociceptors, exacerbating inflammation and pain signal. Analysis of signaling networks indicates that PKA is downregulated in trigeminal neurons from MOH mice, relieving its inhibitory action on NO-Nav1.9 coupling. Thus, anomalous activation of Nav1.9 channels by NO, as a result of chronic medication, promotes MOH.


Asunto(s)
Cefaleas Secundarias/patología , Trastornos Migrañosos/patología , Canal de Sodio Activado por Voltaje NAV1.9/metabolismo , Neuronas Aferentes/metabolismo , Óxido Nítrico/metabolismo , Triptaminas/efectos adversos , Animales , Péptido Relacionado con Gen de Calcitonina/metabolismo , Degranulación de la Célula/fisiología , Células Cultivadas , Femenino , Cefaleas Secundarias/inducido químicamente , Hiperalgesia/fisiopatología , Masculino , Mastocitos/patología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Canal de Sodio Activado por Voltaje NAV1.9/genética , Neuronas Aferentes/efectos de los fármacos , Nociceptores/fisiología , Dolor/fisiopatología , Uso Excesivo de Medicamentos Recetados/efectos adversos
2.
Gastroenterology ; 157(2): 522-536.e2, 2019 08.
Artículo en Inglés | MEDLINE | ID: mdl-31075226

RESUMEN

BACKGROUND & AIMS: Proper colon function requires signals from extrinsic primary afferent neurons (ExPANs) located in spinal ganglia. Most ExPANs express the vanilloid receptor TRPV1, and a dense plexus of TRPV1-positive fibers is found around myenteric neurons. Capsaicin, a TRPV1 agonist, can initiate activity in myenteric neurons and produce muscle contraction. ExPANs might therefore form motility-regulating synapses onto myenteric neurons. ExPANs mediate visceral pain, and myenteric neurons mediate colon motility, so we investigated communication between ExPANs and myenteric neurons and the circuits by which ExPANs modulate colon function. METHODS: In live mice and colon tissues that express a transgene encoding the calcium indicator GCaMP, we visualized levels of activity in myenteric neurons during smooth muscle contractions induced by application of capsaicin, direct colon stimulation, stimulation of ExPANs, or stimulation of preganglionic parasympathetic neuron (PPN) axons. To localize central targets of ExPANs, we optogenetically activated TRPV1-expressing ExPANs in live mice and then quantified Fos immunoreactivity to identify activated spinal neurons. RESULTS: Focal electrical stimulation of mouse colon produced phased-locked calcium signals in myenteric neurons and produced colon contractions. Stimulation of the L6 ventral root, which contains PPN axons, also produced myenteric activation and contractions that were comparable to those of direct colon stimulation. Surprisingly, capsaicin application to the isolated L6 dorsal root ganglia, which produced robust calcium signals in neurons throughout the ganglion, did not activate myenteric neurons. Electrical activation of the ganglia, which activated even more neurons than capsaicin, did not produce myenteric activation or contractions unless the spinal cord was intact, indicating that a complete afferent-to-efferent (PPN) circuit was necessary for ExPANs to regulate myenteric neurons. In TRPV1-channel rhodopsin-2 mice, light activation of ExPANs induced a pain-like visceromotor response and expression of Fos in spinal PPN neurons. CONCLUSIONS: In mice, ExPANs regulate myenteric neuron activity and smooth muscle contraction via a parasympathetic spinal circuit, linking sensation and pain to motility.


Asunto(s)
Colon/fisiopatología , Neuronas Aferentes/fisiología , Peristaltismo/fisiología , Dolor Visceral/fisiopatología , Animales , Técnicas Biosensibles/métodos , Capsaicina/administración & dosificación , Colon/efectos de los fármacos , Colon/inervación , Modelos Animales de Enfermedad , Femenino , Ganglios Espinales/citología , Humanos , Masculino , Ratones , Ratones Transgénicos , Contracción Muscular/efectos de los fármacos , Contracción Muscular/fisiología , Músculo Liso/inervación , Músculo Liso/fisiopatología , Plexo Mientérico/citología , Plexo Mientérico/efectos de los fármacos , Neuronas Aferentes/efectos de los fármacos , Optogenética , Peristaltismo/efectos de los fármacos , Canales Catiónicos TRPV/genética , Canales Catiónicos TRPV/metabolismo , Dolor Visceral/inducido químicamente
3.
Exp Brain Res ; 237(7): 1629-1641, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-30949729

RESUMEN

Previous studies from our laboratory showed that in the anesthetized cat, the intradermal injection of capsaicin in the hindpaw facilitated the intraspinal field potentials (IFPs) evoked by stimulation of the intermediate and high-threshold myelinated fibers in the posterior articular nerve (PAN). The capsaicin-induced facilitation was significantly reduced 3-4 h after the injection, despite the persistence of hindpaw inflammation. Although this effect was attributed to an incremented descending inhibition acting on the spinal pathways, it was not clear if it was set in operation once the capsaicin-induced effects exceeded a certain threshold, or if it was continuously operating to keep the increased neuronal activation within manageable limits. To evaluate the changes in descending inhibition, we now examined the effects of successive reversible spinal blocks on the amplitude of the PAN IFPs evoked at different times after the intradermal injection of capsaicin. We found that after capsaicin the PAN IFPs recorded in laminae III-V by activation of high-threshold nociceptive Aδ myelinated fibers increased gradually during successive reversible spinal blocks, while the IFPs evoked by intermediate and low threshold proprioceptive Aß afferents were only slightly affected. It is concluded that during the development of the central sensitization produced by capsaicin, there is a gradual increase of descending inhibition that tends to limit the nociceptive-induced facilitation, mainly by acting on the neuronal populations receiving inputs from the capsaicin-activated afferents without significantly affecting the information on joint angle transmitted by the low threshold afferents.


Asunto(s)
Capsaicina/farmacología , Neuronas Aferentes/efectos de los fármacos , Nociceptores/efectos de los fármacos , Células del Asta Posterior/efectos de los fármacos , Tractos Piramidales/efectos de los fármacos , Fármacos del Sistema Sensorial/farmacología , Animales , Gatos , Femenino , Masculino , Neuronas Aferentes/fisiología , Nociceptores/fisiología , Células del Asta Posterior/fisiología , Tractos Piramidales/fisiología
4.
PLoS One ; 14(4): e0215036, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-30970000

RESUMEN

OBJECTIVE: We aimed to refine electroneurogram techniques for monitoring hypogastric nerve activity during bladder filling, and then examined nerve activity in normal intact versus acutely decentralized bladders. METHODS: Effects of electrical stimulation of hypogastric nerves or lumbar ventral roots on detrusor pressure were examined, as were effects of isoflurane versus propofol anesthetics on hypogastric nerve stimulation evoked pressure. Hypogastric nerve activity was then recorded using custom-made bipolar cuff electrodes during bladder filling before and after its transection between the spinal cord and electrode to eliminate efferent nerve signals. RESULTS: Electrical stimulation of hypogastric nerves evoked low amplitude detrusor pressures that did not differ between the two anesthetics. Upper lumbar (L2) ventral root stimulation evoked detrusor pressures were suppressed, yet not eliminated, after transection of hypogastric nerves and all spinal roots below L5. Afferent and efferent hypogastric nerve activity did not change with bladder filling in neuronally intact bladders yet decreased in decentralized bladders. No change in afferent activity was observed during bladder filling in either intact or decentralized bladders. CONCLUSIONS: These findings indicate that a more complete decentralized bladder model should include transection of lumbosacral spinal roots innervating the bladder as well as hypogastric nerves. These refined electroneurogram recording methods may be suitable for evaluating the effectiveness of nerve transfer surgeries for bladder reinnervation by monitoring sensory activity in the transferred nerve.


Asunto(s)
Estimulación Eléctrica , Raíces Nerviosas Espinales/fisiología , Sistema Nervioso Simpático/fisiología , Vejiga Urinaria/fisiología , Animales , Perros , Potenciales Evocados , Isoflurano/farmacología , Neuronas Aferentes/efectos de los fármacos , Neuronas Aferentes/fisiología , Neuronas Eferentes/efectos de los fármacos , Neuronas Eferentes/fisiología , Propofol/farmacología , Raíces Nerviosas Espinales/efectos de los fármacos , Sistema Nervioso Simpático/efectos de los fármacos
5.
Neuroscience ; 404: 119-129, 2019 04 15.
Artículo en Inglés | MEDLINE | ID: mdl-30710669

RESUMEN

The aims of the study were to compare effects of baclofen, a GABAB receptor agonist commonly used as an antispastic drug, on direct current (DC) evoked long-lasting changes in the excitability of afferent fibers traversing the dorsal columns and their terminal branches in the spinal cord, and to examine whether baclofen interferes with the development and expression of these changes. The experiments were performed on deeply anesthetized rats by analyzing the effects of DC before, during and following baclofen administration. Muscle and skin afferent fibers within the dorsal columns were stimulated epidurally and changes in their excitability were investigated following epidural polarization by 1.0-1.1 µA subsequent to i.v. administration of baclofen. Epidural polarization increased the excitability of these fibers during post-polarization periods of at least 1 h. The facilitation was as potent as in preparations that were not pretreated with baclofen, indicating that the advantages of combining epidural polarization with epidural stimulation would not be endangered by pharmacological antispastic treatment with baclofen. In contrast, baclofen-reduced effects of intraspinal stimulation combined with intraspinal polarization (0.3 µA) of terminal axonal branches of the afferents within the dorsal horn or in motor nuclei, whether administered ionophoretically or intravenously. Effects of DC on monosynaptically evoked synaptic actions of these fibers (extracellular field potentials) were likewise reduced by baclofen. The study thus provides further evidence for differential effects of DC on afferent fibers in the dorsal columns and the preterminal branches of these fibers and their involvement in spinal plasticity.


Asunto(s)
Baclofeno/farmacología , Agonistas de Receptores GABA-B/farmacología , Plasticidad Neuronal/fisiología , Neuronas Aferentes/fisiología , Médula Espinal/fisiología , Animales , Estimulación Eléctrica/métodos , Femenino , Masculino , Plasticidad Neuronal/efectos de los fármacos , Neuronas Aferentes/efectos de los fármacos , Ratas , Ratas Wistar , Médula Espinal/efectos de los fármacos
6.
Am J Physiol Renal Physiol ; 316(4): F703-F711, 2019 04 01.
Artículo en Inglés | MEDLINE | ID: mdl-30672315

RESUMEN

This study in α-chloralose-anesthetized cats revealed a role of hypogastric nerve afferent axons in nociceptive bladder activity induced by bladder irritation using 0.25% acetic acid (AA). In cats with intact hypogastric and pelvic nerves, AA irritation significantly ( P < 0.05) reduced bladder capacity to 45.0 ± 5.7% of the control capacity measured during a saline cystometrogram (CMG). In cats with the hypogastric nerves transected bilaterally, AA irritation also significantly ( P < 0.05) reduced bladder capacity, but the change was significantly smaller (capacity reduced to 71.5 ± 10.6% of saline control, P < 0.05) than that in cats with an intact hypogastric nerve. However, application of hypogastric nerve stimulation (HGNS: 20 Hz, 0.2 ms pulse width) to the central end of the transected nerves at an intensity (16 V) strong enough to activate C-fiber afferent axons facilitated the effect of AA irritation and further ( P < 0.05) reduced bladder capacity to 48.4 ± 7.4% of the saline control. This facilitation by HGNS was effective only at selected frequencies (1, 20, and 30 Hz) when the stimulation intensity was above the threshold for activating C-fibers. Tramadol (an analgesic agent) at 3 mg/kg iv completely blocked the nociceptive bladder activity and eliminated the facilitation by HGNS. HGNS did not alter non-nociceptive bladder activity induced by saline distention of the bladder. These results indicate that sympathetic afferents in the hypogastric nerve play an important role in the facilitation of the nociceptive bladder activity induced by bladder irritation that activates the silent C-fibers in the pelvic nerve.


Asunto(s)
Neuronas Aferentes/fisiología , Nocicepción/fisiología , Sistema Nervioso Simpático/fisiología , Vejiga Urinaria/fisiología , Ácido Acético , Analgésicos Opioides/farmacología , Animales , Axones/fisiología , Gatos , Estimulación Eléctrica , Femenino , Masculino , Fibras Nerviosas Amielínicas/fisiología , Neuronas Aferentes/efectos de los fármacos , Nocicepción/efectos de los fármacos , Sistema Nervioso Simpático/efectos de los fármacos , Tramadol/farmacología
7.
Mol Neurobiol ; 56(8): 5917-5933, 2019 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-30689196

RESUMEN

As mitochondrial dysfunction is evident in neurodegenerative disorders that are accompanied by pain, we generated inducible mutant mice with disruption of mitochondrial respiratory chain complex IV, by COX10 deletion limited to sensory afferent neurons through the use of an Advillin Cre-reporter. COX10 deletion results in a selective energy-deficiency phenotype with minimal production of reactive oxygen species. Mutant mice showed reduced activity of mitochondrial respiratory chain complex IV in many sensory neurons, increased ADP/ATP ratios in dorsal root ganglia and dorsal spinal cord synaptoneurosomes, as well as impaired mitochondrial membrane potential, in these synaptoneurosome preparations. These changes were accompanied by marked pain hypersensitivity in mechanical and thermal (hot and cold) tests without altered motor function. To address the underlying basis, we measured Ca2+ fluorescence responses of dorsal spinal cord synaptoneurosomes to activation of the GluK1 (kainate) receptor, which we showed to be widely expressed in small but not large nociceptive afferents, and is minimally expressed elsewhere in the spinal cord. Synaptoneurosomes from mutant mice showed greatly increased responses to GluK1 agonist. To explore whether altered nucleotide levels may play a part in this hypersensitivity, we pharmacologically interrogated potential roles of AMP-kinase and ADP-sensitive purinergic receptors. The ADP-sensitive P2Y1 receptor was clearly implicated. Its expression in small nociceptive afferents was increased in mutants, whose in vivo pain hypersensitivity, in mechanical, thermal and cold tests, was reversed by a selective P2Y1 antagonist. Energy depletion and ADP elevation in sensory afferents, due to mitochondrial respiratory chain complex IV deficiency, appear sufficient to induce pain hypersensitivity, by ADP activation of P2Y1 receptors.


Asunto(s)
Complejo IV de Transporte de Electrones/genética , Hipersensibilidad/patología , Mitocondrias/metabolismo , Mutación/genética , Neuronas Aferentes/patología , Dolor/patología , Receptores Purinérgicos P2Y1/metabolismo , Adenosina Difosfato/metabolismo , Adenosina Monofosfato/metabolismo , Transferasas Alquil y Aril/metabolismo , Animales , Conducta Animal , Calcio/metabolismo , Células Cultivadas , Complejo IV de Transporte de Electrones/metabolismo , Fluorescencia , Ganglios Espinales/efectos de los fármacos , Ganglios Espinales/metabolismo , Hipersensibilidad/complicaciones , Proteínas de la Membrana/metabolismo , Ratones Endogámicos C57BL , Ratones Transgénicos , Mitocondrias/efectos de los fármacos , Neuronas Aferentes/efectos de los fármacos , Neuronas Aferentes/metabolismo , Nocicepción/efectos de los fármacos , Dolor/complicaciones , Fenotipo , Antagonistas del Receptor Purinérgico P2Y/farmacología , Receptores de Ácido Kaínico/metabolismo , Médula Espinal/patología , Sinapsis/efectos de los fármacos , Sinapsis/metabolismo
8.
Biomed Pharmacother ; 109: 377-385, 2019 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-30399572

RESUMEN

Resiniferatoxin (RTX), a selective transient receptor potential vanilloid 1 (TRPV1) receptor agonist, can eliminate TRPV1+ primary sensory afferents and blunt cardiac sympathetic afferent reflex for a relatively long period. The present study determined the effects of intrathecal RTX administration on transverse aortic constriction (TAC)-induced cardiac dysfunction and cardiac remodeling in rats. Five days before TAC, RTX (2 µg/10 µl) was injected intrathecally into the T2/T3 interspace of rats. Cardiac sympathetic nerve activities (CSNAs) and cardiac structure and function were determined eight weeks after TAC. Intrathecal RTX administration abolished TRPV1 expression in the dorsal horn and reduced over-activated CSNA in the TAC rat model. Hemodynamic analysis revealed that RTX reduced left ventricular end-diastolic pressure, indicating the improvement of cardiac compliance. Histologic analysis, real-time reverse transcription-polymerase chain reaction, and Western blots showed that RTX prevented TAC-induced cardiac hypertrophy, cardiac fibrosis, and cardiac apoptosis and reduced the expression of apoptotic proteins and myocardial mRNAs. In conclusion, these results demonstrate that focal chemo-ablation of TRPV1+ afferents in the spinal cord protects the heart from pressure overload-induced cardiac remodeling and cardiac dysfunction, which suggest a novel promising therapeutic method for cardiac hypertrophy and diastolic dysfunction.


Asunto(s)
Técnicas de Ablación/métodos , Cardiomegalia/prevención & control , Cardiotónicos/administración & dosificación , Diterpenos/administración & dosificación , Corazón/efectos de los fármacos , Neuronas Aferentes/efectos de los fármacos , Médula Espinal/efectos de los fármacos , Animales , Cardiomegalia/metabolismo , Cardiomegalia/patología , Corazón/inervación , Corazón/fisiología , Inyecciones Espinales , Masculino , Ratas , Ratas Sprague-Dawley , Médula Espinal/metabolismo , Médula Espinal/cirugía , Asta Dorsal de la Médula Espinal/efectos de los fármacos , Asta Dorsal de la Médula Espinal/fisiología , Canales Catiónicos TRPV/agonistas
9.
Neurosci Lett ; 696: 87-92, 2019 03 23.
Artículo en Inglés | MEDLINE | ID: mdl-30553866

RESUMEN

Temperature plays a critical role in the sensation of airflow in the nasal mucosa. Neural activities of the ethmoidal nerve, a trigeminal afferent, responding to airflow are suppressed by warm airflow, whereas cold airflow enhances the ethmoidal nerve activities, which is mimicked by application of menthol, a cold-sensitive TRPM8 receptor agonist. However, it has been an open issue how menthol modulates the spatiotemporal profiles of neural activities of somatosensory cortical neurons. In this study, we assessed neural responses to an air puff stimulation (100 ms) to the nasal cavity in the absence or presence of l-menthol using an optical imaging technique with a voltage-sensitive dye in the primary cortex (S1) of urethane-anesthetized rats. A weak air puff application (15 psi) without l-menthol induced neural excitation in a part of the contralateral S1. The air puff stimulation with l-menthol significantly increased the optical signal intensity, expanded the activated area, and shortened the latency, compared to those in the absence of l-menthol. These results suggest that activation of cold-sensitive TRPM8 receptors sharpens airflow sensation in the nasal cavity and expands the receptive field, especially toward the pharynx, which may contribute to enhanced flavor perception.


Asunto(s)
Aire , Mentol/farmacología , Cavidad Nasal/efectos de los fármacos , Imagen Óptica , Animales , Frío/efectos adversos , Masculino , Mucosa Nasal/efectos de los fármacos , Neuronas Aferentes/efectos de los fármacos , Neuronas Aferentes/metabolismo , Imagen Óptica/métodos , Ratas Sprague-Dawley , Corteza Somatosensorial/efectos de los fármacos , Corteza Somatosensorial/metabolismo
10.
J Mol Neurosci ; 68(3): 348-356, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-30022438

RESUMEN

Pituitary adenylate cyclase-activating polypeptide (PACAP; Adcyap1) and its cognate PAC1 receptor (Adcyap1r1) have tissue-specific distributions in the lower urinary tract (LUT). The afferent limb of the micturition reflex is often compromised following bladder injury, disease, and inflammatory conditions. We have previously demonstrated that PACAP signaling contributes to increased voiding frequency and decreased bladder capacity with cystitis. Thus, the present studies investigated the sensory components (e.g., urothelial cells, bladder afferent nerves) of the urinary bladder that may underlie the pathophysiology of aberrant PACAP activation. We utilized bladder-pelvic nerve preparations and urothelial sheet preparations to characterize PACAP-induced bladder afferent nerve discharge with distention and PACAP-induced Ca2+ activity, respectively. We determined that PACAP38 (100 nM) significantly (p ≤ 0.01) increased bladder afferent nerve activity with distention that was blocked with a PAC1/VPAC2 receptor antagonist PACAP6-38 (300 nM). PACAP38 (100 nM) also increased Ca2+ activity in urothelial cells over that observed in control preparations. Taken together, these results establish a role for PACAP signaling in bladder sensory components (e.g., urothelial cells, bladder afferent nerves) that may ultimately facilitate increased voiding frequency.


Asunto(s)
Potenciales de Acción , Calcio/metabolismo , Neuronas Aferentes/metabolismo , Polipéptido Hipofisario Activador de la Adenilato-Ciclasa/metabolismo , Urotelio/metabolismo , Animales , Masculino , Ratones , Ratones Endogámicos C57BL , Neuronas Aferentes/efectos de los fármacos , Neuronas Aferentes/fisiología , Polipéptido Hipofisario Activador de la Adenilato-Ciclasa/farmacología , Transducción de Señal , Urotelio/efectos de los fármacos
11.
Life Sci ; 218: 89-95, 2019 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-30580018

RESUMEN

AIMS: To examine the effects of RQ-00434739, a novel selective TRPM8 antagonist, on deep body temperature (DBT) and normal bladder sensory function and overactivity and its associated facilitation of mechanosensitive primary bladder single-unit afferent activities (SAAs) induced by intravesical l-menthol or prostaglandin E2 (PGE2) instillation in rats. MAIN METHODS: The effect of RQ-00434739 on DBT was evaluated using intravenous administration of RQ-00434739 (1 mg/kg) or its vehicle under urethane anaesthesia. Cystometry (CMG) was performed on conscious and freely moving rats. SAAs were measured from the left L6 dorsal root under urethane anaesthesia, and the fibers were grouped as Aδ- or C-fiber based on their conduction velocity. For both CMG and SAA measurements, after baseline recording with saline instillation, further recording was performed with intravesical l-menthol (6 mM) or PGE2 (60 µM) instillation after pretreatment with intravenous RQ-00434739 (1 mg/kg) or its vehicle. KEY FINDINGS: RQ-00434739 did not significantly affect DBT. In CMG measurements, RQ-00434739 administration increased mean voided volume. Both l-menthol and PGE2 instillation decreased mean voided volume following vehicle pretreatment, whereas such effects were not observed following RQ-00434739 pretreatment. In SAA measurements, either l-menthol or PGE2 instillations increased SAAs of C-fibers, but not SAAs of Aδ-fibers, in the presence of vehicle. RQ-00434739 pretreatment significantly inhibited the l-menthol- and PGE2-induced activation of C-fiber SAAs. SIGNIFICANCE: The present results demonstrate that blockade of TRPM8 channels can inhibit the pathological activation of mechanosensitive C-fibers and suggest that RQ-00434739 may be a promising therapeutic drug candidate for bladder hypersensitive disorders without affecting DBT.


Asunto(s)
Vías Aferentes/efectos de los fármacos , Regulación de la Temperatura Corporal/efectos de los fármacos , Dinoprostona/toxicidad , Neuronas Aferentes/efectos de los fármacos , Canales Catiónicos TRPM/antagonistas & inhibidores , Enfermedades de la Vejiga Urinaria/prevención & control , Vejiga Urinaria/efectos de los fármacos , Animales , Células Cultivadas , Masculino , Neuronas Aferentes/metabolismo , Neuronas Aferentes/patología , Oxitócicos/toxicidad , Ratas , Ratas Sprague-Dawley , Vejiga Urinaria/inervación , Vejiga Urinaria/metabolismo , Enfermedades de la Vejiga Urinaria/inducido químicamente , Enfermedades de la Vejiga Urinaria/metabolismo
12.
Sci Rep ; 8(1): 15916, 2018 10 29.
Artículo en Inglés | MEDLINE | ID: mdl-30374145

RESUMEN

Capsaicin-sensitive afferents have complex regulatory functions in the joints orchestrated via neuropeptides. This study aimed to determine their role in the collagen-antibody induced rheumatoid arthritis model. Capsaicin-sensitive nerves were defunctionalized by the capsaicin receptor agonist resiniferatoxin in C57Bl/6 mice. Arthritis was induced by the ArithroMab antibody cocktail and adjuvant. Arthritis was monitored by measuring body weight, joint edema by plethysmometry, arthritis severity by clinical scoring, mechanonociceptive threshold by plantar esthesiometry, thermonociceptive threshold by hot plate, cold tolerance by paw withdrawal latency from 0 °C water. Grasping ability was determined by the wire-grid grip test. Bone structure was evaluated by in vivo micro-CT and histology. Arthritic animals developed a modest joint edema, mechanical and cold hyperalgesia, weight loss, and a diminished grasping function, while thermal hyperalgesia is absent in the model. Desensitised mice displayed reduced arthritis severity, edema, and mechanical hyperalgesia, however, cold hyperalgesia was significantly greater in this group. Arthritic controls displayed a transient decrease of bone volume and an increased porosity, while bone density and trabecularity increased in desensitised mice. The activation of capsaicin-sensitive afferents increases joint inflammation and mechanical hyperalgesia, but decreases cold allodynia. It also affects inflammatory bone structural changes by promoting bone resorption.


Asunto(s)
Artritis Experimental/patología , Capsaicina/farmacología , Neuronas Aferentes/efectos de los fármacos , Animales , Articulación del Tobillo/diagnóstico por imagen , Articulación del Tobillo/patología , Anticuerpos/inmunología , Artritis Experimental/tratamiento farmacológico , Artritis Experimental/metabolismo , Peso Corporal/efectos de los fármacos , Modelos Animales de Enfermedad , Diterpenos/farmacología , Diterpenos/uso terapéutico , Edema/patología , Hiperalgesia/prevención & control , Masculino , Ratones , Ratones Endogámicos C57BL , Neuronas Aferentes/metabolismo , Índice de Severidad de la Enfermedad , Microtomografía por Rayos X
13.
Biochem Biophys Res Commun ; 506(3): 498-503, 2018 11 30.
Artículo en Inglés | MEDLINE | ID: mdl-30361095

RESUMEN

ATP in the suburothelial layer is released from the bladder urothelium by mechanical stimuli. ATP directly activates purinergic receptors that are expressed on primary bladder afferent neurons and induces the micturition reflex. Although ATP is also released to the bladder lumen from the bladder urothelium, the role of ATP in the bladder lumen is unknown. Recently, clinical studies have reported that urinary ATP levels are much higher in patients with an overactive bladder than healthy controls. These results suggest that ATP in the bladder lumen is also involved in the micturition reflex. In this study, we performed intravesical ATP instillation in the mouse bladder. We evaluated urinary function with novel reliable methods using improved cystometry and ultrasonography, which we previously established. We found that intravesical ATP instillation induced urinary frequency because of activation of bladder afferent nerves without inflammatory changes in the bladder or an increase in post-void residual urine. These results suggest that not only ATP in the suburothelial layer, but also ATP in the bladder lumen, are involved in enhancement of the micturition reflex.


Asunto(s)
Adenosina Trifosfato/farmacología , Inflamación/patología , Neuronas Aferentes/patología , Vejiga Urinaria Hiperactiva/patología , Vejiga Urinaria/inervación , Micción/efectos de los fármacos , Adenosina Trifosfato/administración & dosificación , Administración Intravesical , Animales , Modelos Animales de Enfermedad , Masculino , Ratones Endogámicos C57BL , Neuronas Aferentes/efectos de los fármacos , Tamaño de los Órganos , Proteínas Proto-Oncogénicas c-fos/metabolismo , Médula Espinal/efectos de los fármacos , Médula Espinal/patología , Vejiga Urinaria/efectos de los fármacos , Vejiga Urinaria/patología
14.
Acta Biochim Biophys Sin (Shanghai) ; 50(12): 1219-1226, 2018 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-30339176

RESUMEN

CC chemokine ligand 2 (CCL2) has been implicated in pathological pain, but the mechanism underlying the pronociceptive effect of CCL2 is not fully understood. Voltage-gated sodium (Nav) channels are important determinants of the excitability of sensory neurons. Hence we tested the hypothesis that CCL2 contributes to inflammatory pain via modulating Nav channel activity of primary afferent neurons. Chronic inflammatory pain was induced in rats by intraplantar injection of the complete Freud adjuvant (CFA) to one of the hind paws. Control rats received intraplantar injection of equal volume of saline. A significant increase of CCL2 mRNA and CCL2 receptor (CCR2) protein expression was detected in the ipsilateral dorsal root ganglion (DRG) in CFA-treated rats. Intraplantar injection of CCL2 protein in the control rats had minimal effect on the paw withdrawal threshold (PWT) in response to mechanical stimulation. However, in CFA-treated rats, intraplantar CCL2 led to an increase in pain responses. Patch-clamp recording of acutely dissociated DRG neurons revealed that CCL2 had minimum effect on the excitability of sensory neurons from control rats. However, CCL2 directly depolarized a large proportion of small to medium-sized sensory neurons from CFA-treated rats. In addition, CCL2 was found to enhance whole-cell TTX-sensitive sodium currents without significantly affecting the TTX-resistant sodium currents and the potassium currents. These results are in agreement with previous reports concerning the involvement of CCL2-CCR2 signaling in inflammatory hyperalgesia and further indicate that enhanced TTX-sensitive channel activity may partly underlie the pronociceptive effects of CCL2.


Asunto(s)
Quimiocina CCL2/farmacología , Inflamación/metabolismo , Neuronas Aferentes/efectos de los fármacos , Dolor/metabolismo , Canales de Sodio/metabolismo , Tetrodotoxina/farmacología , Animales , Quimiocina CCL2/genética , Quimiocina CCL2/metabolismo , Sinergismo Farmacológico , Adyuvante de Freund , Ganglios Espinales/citología , Ganglios Espinales/metabolismo , Expresión Génica/efectos de los fármacos , Inflamación/inducido químicamente , Masculino , Potenciales de la Membrana/efectos de los fármacos , Neuronas Aferentes/metabolismo , Técnicas de Placa-Clamp , Ratas Sprague-Dawley , Bloqueadores de los Canales de Sodio/farmacología , Canales de Sodio/genética
15.
Sci Rep ; 8(1): 13397, 2018 09 07.
Artículo en Inglés | MEDLINE | ID: mdl-30194442

RESUMEN

Cone snails are a diverse group of predatory marine invertebrates that deploy remarkably complex venoms to rapidly paralyse worm, mollusc or fish prey. ω-Conotoxins are neurotoxic peptides from cone snail venoms that inhibit Cav2.2 voltage-gated calcium channel, demonstrating potential for pain management via intrathecal (IT) administration. Here, we isolated and characterized two novel ω-conotoxins, MoVIA and MoVIB from Conus moncuri, the first to be identified in vermivorous (worm-hunting) cone snails. MoVIA and MoVIB potently inhibited human Cav2.2 in fluorimetric assays and rat Cav2.2 in patch clamp studies, and both potently displaced radiolabeled ω-conotoxin GVIA (125I-GVIA) from human SH-SY5Y cells and fish brain membranes (IC50 2-9 pM). Intriguingly, an arginine at position 13 in MoVIA and MoVIB replaced the functionally critical tyrosine found in piscivorous ω-conotoxins. To investigate its role, we synthesized MoVIB-[R13Y] and MVIIA-[Y13R]. Interestingly, MVIIA-[Y13R] completely lost Cav2.2 activity and MoVIB-[R13Y] had reduced activity, indicating that Arg at position 13 was preferred in these vermivorous ω-conotoxins whereas tyrosine 13 is preferred in piscivorous ω-conotoxins. MoVIB reversed pain behavior in a rat neuropathic pain model, confirming that vermivorous cone snails are a new source of analgesic ω-conotoxins. Given vermivorous cone snails are ancestral to piscivorous species, our findings support the repurposing of defensive venom peptides in the evolution of piscivorous Conidae.


Asunto(s)
Analgésicos/química , Bloqueadores de los Canales de Calcio/química , Evolución Molecular , omega-Conotoxinas/química , Analgésicos/farmacología , Analgésicos/uso terapéutico , Animales , Bloqueadores de los Canales de Calcio/farmacología , Bloqueadores de los Canales de Calcio/uso terapéutico , Canales de Calcio Tipo N/metabolismo , Línea Celular Tumoral , Células Cultivadas , Ganglios Espinales/citología , Humanos , Neuralgia/tratamiento farmacológico , Neuronas Aferentes/efectos de los fármacos , Ratas , Ratas Wistar , Caracoles , omega-Conotoxinas/genética , omega-Conotoxinas/farmacología , omega-Conotoxinas/uso terapéutico
16.
Neuron ; 99(6): 1274-1288.e6, 2018 09 19.
Artículo en Inglés | MEDLINE | ID: mdl-30236284

RESUMEN

Primary afferents are known to be inhibited by kappa opioid receptor (KOR) signaling. However, the specific types of somatosensory neurons that express KOR remain unclear. Here, using a newly developed KOR-cre knockin allele, viral tracing, single-cell RT-PCR, and ex vivo recordings, we show that KOR is expressed in several populations of primary afferents: a subset of peptidergic sensory neurons, as well as low-threshold mechanoreceptors that form lanceolate or circumferential endings around hair follicles. We find that KOR acts centrally to inhibit excitatory neurotransmission from KOR-cre afferents in laminae I and III, and this effect is likely due to KOR-mediated inhibition of Ca2+ influx, which we observed in sensory neurons from both mouse and human. In the periphery, KOR signaling inhibits neurogenic inflammation and nociceptor sensitization by inflammatory mediators. Finally, peripherally restricted KOR agonists selectively reduce pain and itch behaviors, as well as mechanical hypersensitivity associated with a surgical incision. These experiments provide a rationale for the use of peripherally restricted KOR agonists for therapeutic treatment.


Asunto(s)
Neuronas Aferentes/efectos de los fármacos , Dolor/tratamiento farmacológico , Receptores Opioides kappa/antagonistas & inhibidores , Transducción de Señal/fisiología , Animales , Axones/fisiología , Ratones , Ratones Transgénicos , Neuronas/fisiología , Nociceptores/efectos de los fármacos , Nociceptores/metabolismo , Manejo del Dolor , Receptores Opioides kappa/metabolismo
17.
J Physiol ; 596(21): 5267-5280, 2018 11.
Artículo en Inglés | MEDLINE | ID: mdl-30192388

RESUMEN

KEY POINTS: Short-latency afferent inhibition (SAI) is modulated by GABAA receptor activity, whereas the pharmacological origin of long-latency afferent inhibition remains unknown. This is the first study to report that long-latency afferent inhibition (LAI) is reduced by the GABAA positive allosteric modulator lorazepam, and that both SAI and LAI are not modulated by the GABAB agonist baclofen. These findings advance our understanding of the neural mechanisms underlying afferent inhibition. ABSTRACT: The afferent volley evoked by peripheral nerve stimulation has an inhibitory influence on transcranial magnetic stimulation induced motor evoked potentials. This phenomenon, known as afferent inhibition, occurs in two phases: short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI). SAI exerts its inhibitory influence via cholinergic and GABAergic activity. The neurotransmitter receptors that mediate LAI remain unclear. The present study aimed to determine whether LAI is contributed by GABAA and/or GABAB receptor activity. In a double-blinded, placebo-controlled study, 2.5 mg of lorazepam (GABAA agonist), 20 mg of baclofen (GABAB agonist) and placebo were administered to 14 males (mean age 22.7 ± 1.9 years) in three separate sessions. SAI and LAI, evoked by stimulation of the median nerve and recorded from the first dorsal interosseous muscle, were quantified before and at the peak plasma concentration following drug ingestion. Results indicate that lorazepam reduced LAI by ∼40% and, in support of previous work, reduced SAI by ∼19%. However, neither SAI, nor LAI were altered by baclofen. In a follow-up double-blinded, placebo-controlled study, 10 returning participants received placebo or 40 mg of baclofen (double the dosage used in Experiment 1). The results obtained indicate that SAI and LAI were unchanged by baclofen. This is the first study to show that LAI is modulated by GABAA receptor activity, similar to SAI, and that afferent inhibition does not appear to be a GABAB mediated process.


Asunto(s)
Baclofeno/farmacología , Agonistas del GABA/farmacología , Lorazepam/farmacología , Inhibición Neural , Neuronas Aferentes/efectos de los fármacos , Humanos , Masculino , Nervio Mediano/efectos de los fármacos , Nervio Mediano/fisiología , Neuronas Aferentes/fisiología , Tiempo de Reacción , Adulto Joven
18.
J Neurophysiol ; 120(6): 2953-2974, 2018 12 01.
Artículo en Inglés | MEDLINE | ID: mdl-30256739

RESUMEN

Activation of GABAA receptors on sensory axons produces a primary afferent depolarization (PAD) that modulates sensory transmission in the spinal cord. While axoaxonic synaptic contacts of GABAergic interneurons onto afferent terminals have been extensively studied, less is known about the function of extrasynaptic GABA receptors on afferents. Thus, we examined extrasynaptic α5GABAA receptors on low-threshold proprioceptive (group Ia) and cutaneous afferents. Afferents were impaled with intracellular electrodes and filled with neurobiotin in the sacrocaudal spinal cord of rats. Confocal microscopy was used to reconstruct the afferents and locate immunolabelled α5GABAA receptors. In all afferents α5GABAA receptors were found throughout the extensive central axon arbors. They were most densely located at branch points near sodium channel nodes, including in the dorsal horn. Unexpectedly, proprioceptive afferent terminals on motoneurons had a relative lack of α5GABAA receptors. When recording intracellularly from these afferents, blocking α5GABAA receptors (with L655708, gabazine, or bicuculline) hyperpolarized the afferents, as did blocking neuronal activity with tetrodotoxin, indicating a tonic GABA tone and tonic PAD. This tonic PAD was increased by repeatedly stimulating the dorsal root at low rates and remained elevated for many seconds after the stimulation. It is puzzling that tonic PAD arises from α5GABAA receptors located far from the afferent terminal where they can have relatively little effect on terminal presynaptic inhibition. However, consistent with the nodal location of α5GABAA receptors, we find tonic PAD helps produce sodium spikes that propagate antidromically out the dorsal roots, and we suggest that it may well be involved in assisting spike transmission in general. NEW & NOTEWORTHY GABAergic neurons are well known to form synaptic contacts on proprioceptive afferent terminals innervating motoneurons and to cause presynaptic inhibition. However, the particular GABA receptors involved are unknown. Here, we examined the distribution of extrasynaptic α5GABAA receptors on proprioceptive Ia afferents. Unexpectedly, these receptors were found preferentially near nodal sodium channels throughout the afferent and were largely absent from afferent terminals. These receptors produced a tonic afferent depolarization that modulated sodium spikes, consistent with their location.


Asunto(s)
Potenciales de la Membrana , Neuronas Aferentes/metabolismo , Propiocepción , Receptores de GABA-A/metabolismo , Canales de Sodio/metabolismo , Médula Espinal/metabolismo , Animales , Femenino , Antagonistas de Receptores de GABA-A/farmacología , Inhibición Neural , Neuronas Aferentes/efectos de los fármacos , Neuronas Aferentes/fisiología , Ratas , Ratas Sprague-Dawley , Médula Espinal/citología , Médula Espinal/fisiología , Sinapsis/metabolismo , Sinapsis/fisiología
19.
Am J Physiol Gastrointest Liver Physiol ; 315(4): G631-G637, 2018 10 01.
Artículo en Inglés | MEDLINE | ID: mdl-30070581

RESUMEN

The central regulating mechanisms of defecation, especially roles of the spinal defecation center, are still unclear. We have shown that monoamines including norepinephrine, dopamine, and serotonin injected into the spinal defecation center cause propulsive contractions of the colorectum. These monoamines are the main neurotransmitters of descending pain inhibitory pathways. Therefore, we hypothesized that noxious stimuli in the colorectum would activate the descending monoaminergic pathways projecting to the spinal defecation center and that subsequently released endogenous monoamine neurotransmitters would enhance colorectal motility. Colorectal motility was measured in rats anesthetized with α-chloralose and ketamine. As a noxious stimulus, capsaicin was administered into the colorectal lumen. To interrupt neuronal transmission in the spinal defecation center, antagonists of norepinephrine, dopamine, and/or serotonin receptors were injected intrathecally at the L6-S1 spinal level, where the spinal defecation center is located. Intraluminal administration of capsaicin, acting on the transient receptor potential vanilloid 1 channel, caused transient propulsive contractions. The effect of capsaicin was abolished by surgical severing of the pelvic nerves or thoracic spinal transection at the T4 level. Capsaicin-induced contractions were blocked by preinjection of D2-like dopamine receptor and 5-hydroxytryptamine subtype 2 and 3 receptor antagonists into the spinal defecation center. We demonstrated that intraluminally administered capsaicin causes propulsive colorectal motility through reflex pathways involving the spinal and supraspinal defecation centers. Our results provide evidence that descending monoaminergic neurons are activated by noxious stimulation to the colorectum, leading to facilitation of colorectal motility. NEW & NOTEWORTHY The present study demonstrates that noxious stimuli in the colorectum activates the descending monoaminergic pathways projecting to the spinal defecation center and that subsequently released endogenous monoamine neurotransmitters, serotonin and dopamine, enhance colorectal motility. Our findings provide a possible explanation of the concurrent appearance of abdominal pain and bowel disorder in irritable bowel syndrome patients. Thus the present study may provide new insights into understanding of mechanisms of colorectal dysfunction involving the central nervous system.


Asunto(s)
Monoaminas Biogénicas/metabolismo , Colon/fisiología , Defecación , Recto/fisiología , Médula Espinal/metabolismo , Animales , Capsaicina/farmacología , Colon/inervación , Masculino , Neuronas Motoras/metabolismo , Neuronas Motoras/fisiología , Contracción Muscular , Neuronas Aferentes/efectos de los fármacos , Neuronas Aferentes/metabolismo , Neuronas Aferentes/fisiología , Ratas , Ratas Sprague-Dawley , Recto/inervación , Reflejo , Fármacos del Sistema Sensorial/farmacología , Médula Espinal/citología , Médula Espinal/fisiología , Canales Catiónicos TRPV/metabolismo
20.
Am J Physiol Renal Physiol ; 315(5): F1217-F1227, 2018 11 01.
Artículo en Inglés | MEDLINE | ID: mdl-30019934

RESUMEN

Literature documents an age-related reduction of bladder sensory function. Transient receptor potential vanilloid (TRPV)1 or TRPV4 channels have been implicated in bladder mechanotransduction. To investigate contributions of TRPV1 or TRPV4 to the age-related reduction of bladder sensory function, bladder responses to capsaicin (CAP; TRPV1 agonist) and GSK-1016790A (GSK; TRPV4 agonist) in retired breeder (RB; 12-15 mo) and young adult (2-3 mo) female rats were compared using multiple methods. Metabolic cage and continuous infusion cystometry [cystometrogram (CMG)] recordings revealed that RB rats exhibit larger bladder capacity and lower voiding frequency. RB rats also have a greater intravesical pressure threshold for micturition; however, the voiding contraction strength was equivalent to that in young rats. CAP (1 µM) or GSK (20 nM) administered intravesically evoked smaller changes in all CMG parameters in RB rats. In vitro, CAP (1 µM) or GSK (20 nM) evoked smaller enhancement of bladder strip contractions, while the muscarinic receptor agonist carbachol (at 100, 300, and 1,000 nM) elicited greater amplitude contractions in RB rats. Patch-clamp recording revealed smaller CAP (100 nM) induced inward currents in bladder primary sensory neurons, and Ca2+ imaging revealed smaller GSK (20 nM) evoked increases in intracellular Ca2+ concentration in urothelial cells in RB rats. These results suggest that RB rats have a decreased bladder sensory function commonly observed in elderly women, and could be used as an animal model to study the underling mechanisms. Reduced functional expression of TRPV1 in bladder afferents or reduced functional expression of urothelial TRPV4 may be associated with the diminished sensory function.


Asunto(s)
Capsaicina/farmacología , Leucina/análogos & derivados , Neuronas Aferentes/efectos de los fármacos , Sulfonamidas/farmacología , Canales Catiónicos TRPV/agonistas , Vejiga Urinaria/efectos de los fármacos , Micción/efectos de los fármacos , Urodinámica/efectos de los fármacos , Urotelio/efectos de los fármacos , Administración Intravesical , Factores de Edad , Envejecimiento , Animales , Señalización del Calcio/efectos de los fármacos , Capsaicina/administración & dosificación , Femenino , Leucina/administración & dosificación , Leucina/farmacología , Mecanotransducción Celular/efectos de los fármacos , Potenciales de la Membrana/efectos de los fármacos , Contracción Muscular/efectos de los fármacos , Neuronas Aferentes/metabolismo , Ratas Sprague-Dawley , Sulfonamidas/administración & dosificación , Canales Catiónicos TRPV/metabolismo , Vejiga Urinaria/inervación , Vejiga Urinaria/metabolismo , Urotelio/metabolismo
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