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1.
J Dent Educ ; 83(6): 663-668, 2019 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-30910932

RESUMEN

Social media have become a major part of an interconnected society, impacting personal and professional lives. This Point/Counterpoint presents two opposing viewpoints on the question of whether social media should be used in dental education as a learning and communication tool for dental students. Viewpoint 1 argues that social media benefit student learning and should be used as a tool in dental education. This argument is based on evidence concerning use of social media and improved learning across health professions, improved peer-peer communication in clinical education, improved engagement in interprofessional education (IPE), and provision of a mechanism for safe and improved communication between practitioners and patients, as well as faculty and students. Viewpoint 2 argues that potential problems and risks in using social media outweigh any benefits found in learning and therefore social media should not be used as a tool in dental education. This viewpoint is supported by evidence of negative effects on learning, the establishment of a negative digital footprint in the public's view, risk of privacy violations when using social media, and the new phenomenon of Internet addiction with its negative physiological effects on social media users.


Asunto(s)
Medios de Comunicación Sociales , Estudiantes de Odontología/estadística & datos numéricos , Comunicación , Educación en Odontología/métodos , Humanos , Aprendizaje , Profesionalismo , Medios de Comunicación Sociales/estadística & datos numéricos , Estudiantes de Odontología/psicología
2.
J Endod ; 41(6): 853-7, 2015 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-25773059

RESUMEN

INTRODUCTION: Endogenous cannabinoid compounds are involved in many physiological processes, including bone metabolism. Cannabinoid receptor 2 (CB2) plays a role in modulating bone density, but published research results are conflicting. Furthermore, the specific role of CB2 in inflammation-induced bone resorption and craniofacial bone density has not been reported. The objective of this study was to assess the role of CB2 in dental pulp exposure-induced periapical bone loss and mandibular bone density. METHODS: Adult female wild-type (WT) and CB2 homozygous knockout (KO) mice were used. Pulp exposures were created unilaterally in the mandibular first molars, and the pulp was left exposed to the oral cavity to induce periapical lesion formation. Mandibles were harvested 26 days after pulp exposure. Mandibular bone mineral density and periapical lesion volume were assessed using micro-computed tomographic imaging. RESULTS: Periapical lesion volume measured on the mesial root of the pulp-exposed first molar was significantly less in CB2 KO than WT mice (P < .05). No significant difference was detected between KO and WT mice in the size of the PDL space measured on the mesial root of the contralateral intact first molar. CB2 KO mice exhibited greater mandibular bone density than WT mice (P < .05). CONCLUSIONS: CB2 plays a role in mandibular bone metabolism. Increased bone density in CB2 KO mice may contribute to the smaller periapical lesion size observed after pulp exposure in KO compared with WT mice. Additional experiments are needed to further elucidate the function of CB2 and clinical implications of cannabinoids on bone and periapical pathosis.


Asunto(s)
Densidad Ósea , Exposición de la Pulpa Dental/metabolismo , Exposición de la Pulpa Dental/patología , Mandíbula/metabolismo , Periodontitis Periapical/metabolismo , Periodontitis Periapical/patología , Receptor Cannabinoide CB2/metabolismo , Animales , Resorción Ósea/patología , Femenino , Ratones , Ratones Noqueados
3.
J Endod ; 40(8): 1190-3, 2014 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-25069931

RESUMEN

INTRODUCTION: The purpose of this study was to compare the fracture resistance to cyclic fatigue of ProTaper Next (PTN; Dentsply Tulsa Dental Specialties, Tulsa, OK), ProTaper Universal (PTU, Dentsply Tulsa Dental Specialties), and Vortex Blue (VB, Dentsply Tulsa Dental Specialties) rotary instruments. METHODS: Twenty instruments each of PTN X1-X5, PTU S1-F5, and VB 20/04-50/04 were rotated until fracture in a simulated canal of 90° and a 5-mm radius using a custom-made testing platform. The number of cycles to fracture (NCF) was calculated. Weibull analysis was used to predict the maximum number of cycles when 99% of the instrument samples survive. RESULTS: VB 20/04-30/04 had significantly higher NCF than PTU S1-F5 and PTN X1-X5. VB 35/04-45/04 had significantly higher NCF than PTU S2-F5 and PTN X2-X5. PTN X1 had higher NCF than PTU S1-F5. PTN X2 had higher NCF than PTU F2-F5. The Weibull distribution predicted the highest number of cycles at which 99% of instruments survive to be 766 cycles for VB 25/04 and the lowest to be 50 cycles for PTU F2. CONCLUSIONS: Under the limitations of this study, VB 20/04-45/04 were more resistant to cyclic fatigue than PTN X2-X5 and PTU S2-F5. PTN X1 and X2 were more resistant to cyclic fatigue than PTU F2-F5. The Weibull distribution appears to be a feasible and potentially clinically relevant model to predict resistance to cyclic fatigue.


Asunto(s)
Preparación del Conducto Radicular/instrumentación , Algoritmos , Aleaciones Dentales/química , Diseño de Equipo , Falla de Equipo , Humanos , Ensayo de Materiales , Níquel/química , Rotación , Estrés Mecánico , Propiedades de Superficie , Análisis de Supervivencia , Factores de Tiempo , Titanio/química
4.
J Endod ; 40(1): 46-50, 2014 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-24331990

RESUMEN

INTRODUCTION: Outcome studies of endodontic treatment of necrotic immature permanent teeth rely on radiographic measures as surrogates of whether the treatment achieved regeneration/revascularization/revitalization. An increase in radiographic root length and/or width is thought to result in a better long-term prognosis for the tooth. In this study, a method to measure radiographic outcomes of endodontic therapies on immature teeth was developed and validated. METHODS: A standardized protocol was developed for measuring the entire area of the root of immature teeth. The radiographic root area (RRA) measurement accounts for the entire surface area of the root as observed on a periapical radiograph. Reviewers were given instructions on how to measure RRA, and they completed measurements on a set of standardized radiographs. RESULTS: The intraclass correlation between the 4 reviewers was 0.9945, suggesting a high concordance among reviewers. There was no effect of the reviewer on the measured RRA values. High concordance was also observed when 1 rater repeated the measurements, with an intraclass correlation value of 0.9995. There was no significant difference in RRA values measured at the 2 sessions by the same rater. Furthermore, significant differences in RRA were detectable between clinical cases that showed obvious continued root development and cases that did not demonstrate discernible root development. CONCLUSIONS: These results suggest that RRA is a valid measure to assess radiographic outcomes in endodontically treated immature teeth, and RRA should be useful in future clinical studies of regenerative endodontic outcomes.


Asunto(s)
Radiografía de Mordida Lateral/normas , Tratamiento del Conducto Radicular/normas , Ápice del Diente/diagnóstico por imagen , Raíz del Diente/diagnóstico por imagen , Diente no Vital/diagnóstico por imagen , Apexificación/normas , Estudios de Factibilidad , Humanos , Variaciones Dependientes del Observador , Odontogénesis/fisiología , Odontometría/normas , Regeneración/fisiología , Reproducibilidad de los Resultados , Ápice del Diente/fisiología , Raíz del Diente/fisiología , Resultado del Tratamiento
5.
J Endod ; 38(8): 1121-5, 2012 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-22794219

RESUMEN

INTRODUCTION: EndoSequence and Vortex are 2 recently developed rotary file systems that are made with traditional nickel-titanium (NiTi) and M-Wire technology, respectively. Previous studies have demonstrated better fatigue resistance of M-Wire rotary files compared with the conventional NiTi file. However, no study has compared the effects of M-Wire and conventional NiTi on transportation and centering ability. Hence, the aim of this study was to evaluate the transportation and centering ability of EndoSequence and Vortex files in mesial roots of mandibular molars by using micro-computed tomography imaging. METHODS: Sixteen extracted mandibular molars with mesiobuccal and mesiolingual canals with separate foramina were used. Preinstrumentation scans of all teeth were taken, and the teeth were divided into 2 groups. In group 1, the mesiobuccal canals were instrumented with Vortex files and the mesiolingual canals with EndoSequence files. In group 2, the mesiobuccal canals were instrumented with EndoSequence files and the mesiolingual canals with Vortex files. Two file sizes were compared, 30/.04 and 40/.04. Postinstrumentation scans were performed, and the 2 scans were compared to determine centering ability and transportation. RESULTS: The amount of transportation at 1, 3, and 5 mm was similar for both file types in both file sizes. Transportation toward the furcation area at 7 mm was greater with the 30/.04 Endosequence files compared with the Vortex 30/.04 files (P < .05), but there was no difference in size 40/.04 files. CONCLUSIONS: Overall, our study does not support the use of one rotary file system over the other (Vortex or EndoSequence) when comparing transportation and centering ability.


Asunto(s)
Cavidad Pulpar/anatomía & histología , Preparación del Conducto Radicular/instrumentación , Aleaciones Dentales/química , Diseño de Equipo , Humanos , Ensayo de Materiales , Diente Molar/anatomía & histología , Níquel/química , Preparación del Conducto Radicular/métodos , Preparación del Conducto Radicular/normas , Rotación , Estrés Mecánico , Propiedades de Superficie , Titanio/química , Ápice del Diente/anatomía & histología , Raíz del Diente/anatomía & histología , Microtomografía por Rayos X
6.
J Endod ; 38(1): 86-90, 2012 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-22152627

RESUMEN

INTRODUCTION: Cannabinoid receptor 2 (CB2) is an intriguing target for the treatment of pain because of its ability to mediate analgesia without psychoactive effects, but little is known about the role of CB2 in pain of endodontic origin. The purpose of this study was to determine the behavioral effects of dental pulp exposure in wild-type (WT) mice and to explore the contribution of CB2 to these behaviors using CB2 knockout (CB2 KO) mice. METHODS: Pulp exposures were created unilaterally in the maxillary and mandibular first molars of female WT and CB2 KO mice. The open field test was used before pulp exposure or sham surgery, and postoperatively at 1 day, 1 week, 2 weeks, and 3 weeks. Mouse body weight and food consumption were recorded preoperatively and postoperatively at 1 day, 2 days, and 1 week. RESULTS: At baseline, CB2 KO mice weighed significantly more and had significantly greater food intake than WT mice. CB2 KO mice exhibited greater anxiety-like behavior in the baseline open field test, having significantly fewer center crossings and less distance traveled than WT mice. Pulp exposure had relatively little effect on the behavior of WT mice. CB2 KO mice with pulp exposures showed a decrease in food intake and body weight after surgery, and pulp exposure resulted in significantly fewer center crossings in the open field test in CB2 KO mice. CONCLUSIONS: Pulp exposure in CB2 KO mice resulted in behaviors consistent with an increase in pain and/or anxiety.


Asunto(s)
Conducta Animal , Exposición de la Pulpa Dental/psicología , Receptor Cannabinoide CB2/fisiología , Animales , Ansiedad/fisiopatología , Ansiedad/psicología , Peso Corporal/fisiología , Exposición de la Pulpa Dental/patología , Exposición de la Pulpa Dental/fisiopatología , Ingestión de Alimentos/fisiología , Femenino , Ratones , Ratones Noqueados , Diente Molar/patología , Dolor/fisiopatología , Dolor/psicología , Enfermedades Periapicales/fisiopatología , Enfermedades Periapicales/psicología , Receptor Cannabinoide CB2/genética , Factores de Tiempo , Caminata/fisiología
7.
J Endod ; 37(2): 235-8, 2011 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-21238809

RESUMEN

BACKGROUND: The purpose of this study was to use micro-computed tomography (micro-CT) scanning to evaluate the efficacy of sonic and passive ultrasonic irrigation (PUI) on calcium hydroxide (Ca[OH](2)) removal and to measure the volume and percentage of Ca(OH)(2) remaining in the root canal system. METHODOLOGY: The root canals of 46 extracted human mandibular molar teeth were prepared with rotary instruments and randomly assigned to two experimental groups (n = 40) as well as positive and negative controls (n = 6). In each experimental group, 20 teeth were assigned to each irrigation protocol, sonic or passive ultrasonic irrigation. All experimental teeth and the positive controls were filled with Ca(OH)(2), whereas the negative control teeth did not receive Ca(OH)(2). All teeth were scanned using micro-CT scanning to determine the dressing volume. After 7 days, the Ca(OH)(2) was removed in the experimental groups using rotary instrumentation only, and the teeth were again scanned using micro-CT scanning to calculate volume and percentage of Ca(OH)(2) removed. Positive control teeth were not subjected to rotary instrumentation. Experimental samples were then irrigated using either sonic or passive ultrasonic and the volume of remaining Ca(OH)(2) was calculated using micro-CT. RESULTS: Remnants of Ca(OH)(2) were found in all experimental groups. No Ca(OH)(2) was found in the negative controls, whereas a mean of 8.7 mm(3) of Ca(OH)(2) was recorded in the positive controls. Rotary plus passive ultrasonic irrigation removed significantly more Ca(OH)(2) (85.7%) than rotary plus sonic irrigation (71.5%) (p < 0.001). CONCLUSIONS: The combination of rotary instrumentation and passive ultrasonic activation for 3 periods of 20 seconds results in significantly lower amounts of Ca(OH)(2) remnants in the canal compared with sonic irrigation.


Asunto(s)
Hidróxido de Calcio , Cavidad Pulpar/efectos de los fármacos , Materiales de Obturación del Conducto Radicular , Irrigantes del Conducto Radicular/administración & dosificación , Preparación del Conducto Radicular/instrumentación , Terapia Combinada , Desbridamiento/instrumentación , Desbridamiento/métodos , Instrumentos Dentales , Humanos , Mandíbula , Diente Molar , Preparación del Conducto Radicular/métodos , Capa de Barro Dentinario , Propiedades de Superficie , Irrigación Terapéutica/instrumentación , Irrigación Terapéutica/métodos , Ultrasonido , Microtomografía por Rayos X
8.
J Orofac Pain ; 21(1): 7-18, 2007.
Artículo en Inglés | MEDLINE | ID: mdl-17312637

RESUMEN

AIMS: To develop and validate a model in which to assess a loss of function associated with temporomandibular joint (TMJ) inflammation in awake, freely moving rats. METHODS: The dependent variable in the model was the time between food rewards (pellets), or interfeeding interval (IFI). IFI was quantified after rats were trained to "bar-press" for food. To validate use of the IFI as a surrogate for temporomandibular disorder (TMD) pain, we determined the impact of several manipulations, including changes in pellet size, the presence and severity of inflammation of the TMJ, masseter muscle, or skin (induced with complete Freund's adjuvant [CFA]), and the influence of preadministration of the non-steroidal anti-inflammatory drug indomethacin (4 mg/kg). Furthermore, in order to determine whether a change in IFI reflected an increase in the time rats spent eating, rats were videotaped, and the amount of time spent eating, grooming, and exploring was analyzed. RESULTS: Inflammation of the TMJ or masseter muscle resulted in significant dose- and pellet size-dependent increases in the IFI. Inflammation of the skin overlying the TMJ had no effect on IFI. Pre-administration of indomethacin reversed the inflammation-induced shift in the IFI. An inflammation-induced increase in IFI was associated with an increase in feeding time. CONCLUSIONS: Our model constitutes a relatively fast and sensitive method with which to assess changes in feeding behavior associated with TMJ inflammation. Only 2 days of training are required to obtain a stable baseline IFI. It is possible to detect changes in IFI as small as 40% with 12 rats per group.


Asunto(s)
Artritis Experimental/fisiopatología , Condicionamiento Operante/fisiología , Conducta Alimentaria/fisiología , Trastornos de la Articulación Temporomandibular/fisiopatología , Adyuvantes Inmunológicos/administración & dosificación , Animales , Antiinflamatorios no Esteroideos/uso terapéutico , Artritis Experimental/patología , Conducta Animal/fisiología , Colorantes , Dermatitis/patología , Dermatitis/fisiopatología , Modelos Animales de Enfermedad , Azul de Evans , Conducta Exploratoria/fisiología , Adyuvante de Freund/administración & dosificación , Aseo Animal/fisiología , Indometacina/uso terapéutico , Masculino , Músculo Masetero/patología , Músculo Masetero/fisiopatología , Miositis/patología , Miositis/fisiopatología , Premedicación , Ratas , Trastornos de la Articulación Temporomandibular/patología , Factores de Tiempo
9.
Am J Physiol Regul Integr Comp Physiol ; 291(2): R343-8, 2006 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-16469833

RESUMEN

The present study was designed to test the hypothesis that estrogen exacerbates inflammation of the temporomandibular joint (TMJ). Evans blue dye was used to quantify plasma extravasation (PE) around the rat TMJ. In an initial set of experiments, TMJ PE was compared in naïve intact male and female rats, as well as in both groups after complete Freund's adjuvant (CFA)-induced inflammation of the TMJ. In contrast to our hypothesis, TMJ PE was significantly greater in both naïve and CFA-inflamed male rats than in females. To determine whether these differences were due to gonadal hormones, four additional groups of rats were studied: gonadectomized (Gx) males and females, Gx males with chronic testosterone (T) replacement, and Gx females with chronic estrogen (E) replacement. The sex difference in baseline TMJ PE appeared to reflect the actions of T. However, in the presence of TMJ inflammation, T augmented TMJ PE in males, while E attenuated TMJ PE in females. Changes in PE were also assessed in the contralateral TMJ. Results from this analysis indicated that there is a transient contralateral increase in TMJ PE in females but not males. Given that there is an inverse relationship between PE and joint damage, our results suggest that testosterone may mitigate, but estrogen may exacerbate, TMJ damage, particularly in the presence of overt inflammation. Importantly, our results may help explain both the higher prevalence and severity of temporomandibular disorder pain in females than males.


Asunto(s)
Estrógenos/farmacología , Inflamación/etiología , Inflamación/fisiopatología , Trastornos de la Articulación Temporomandibular/inmunología , Testosterona/farmacología , Animales , Femenino , Terapia de Reemplazo de Hormonas , Inflamación/inducido químicamente , Masculino , Orquiectomía , Ovariectomía , Ratas , Caracteres Sexuales , Articulación Temporomandibular , Trastornos de la Articulación Temporomandibular/inducido químicamente
10.
Neurosignals ; 14(4): 147-57, 2005.
Artículo en Inglés | MEDLINE | ID: mdl-16215297

RESUMEN

One of the most prominent signs of tissue injury and inflammation is pain and pain continues to be the primary reason people seek medical attention. Inflammatory pain reflects, at least in part, an increase in the excitability, or sensitization, of subpopulations of primary afferent neurons. While the sensitization of high threshold afferents was observed almost 40 years ago, the basis for this phenomenon continues to be an active and fertile area of research today. This review will summarize recent advances in our mechanistic understanding of sensitization, focusing on four general areas where re search has been most active or productive. These include: (1) the characterization of second messenger pathways underlying inflammation-induced changes in afferent excitability; (2) the impact of previous injury on the afferent response to subsequent inflammation; (3) the impact of target of innervation on the specific afferent response to inflammation, and (4) the impact of sex hormones on the sensitization of high threshold afferents. Work in these areas highlights how much has been learned about this process as well as how much there is yet to learn.


Asunto(s)
Inflamación/patología , Inflamación/fisiopatología , Neuronas Aferentes/fisiología , Dolor/fisiopatología , Vías Aferentes/fisiopatología , Animales , Hormonas/metabolismo , Mecanorreceptores , Sistemas de Mensajero Secundario/fisiología
11.
Neurosci Lett ; 384(3): 294-9, 2005 Aug 26.
Artículo en Inglés | MEDLINE | ID: mdl-15908117

RESUMEN

Inflammation-induced changes in voltage-gated sodium currents (I(Na)) in primary afferent neurons may contribute to hyperexcitability and pain. The present study was designed to test the hypothesis that persistent inflammation of the temporomandibular joint (TMJ) increases I(Na) in TMJ afferents. Acutely dissociated retrogradely labeled TMJ afferents were studied using whole-cell patch clamp techniques three days following Complete Freund's Adjuvant-induced inflammation of the TMJ. Inflammation was associated with a decrease in tetrodotoxin (TTX)-sensitive Na+ conductance and no significant change in slowly inactivating TTX-resistant Na+ conductance. However, inflammation increased the excitability of TMJ afferents. These results suggest that changes in ion channels other than those underlying TTX-sensitive and the slowly inactivating TTX-resistant Na+ conductance are likely to account for the inflammation-induced increase in the excitability of TMJ afferents.


Asunto(s)
Inflamación/fisiopatología , Neuronas Aferentes/metabolismo , Canales de Sodio/metabolismo , Sodio/metabolismo , Trastornos de la Articulación Temporomandibular/fisiopatología , Articulación Temporomandibular/inervación , Articulación Temporomandibular/fisiopatología , Potenciales de Acción , Vías Aferentes/efectos de los fármacos , Vías Aferentes/fisiopatología , Animales , Células Cultivadas , Inflamación/complicaciones , Activación del Canal Iónico/efectos de los fármacos , Masculino , Neuronas Aferentes/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Canales de Sodio/efectos de los fármacos , Trastornos de la Articulación Temporomandibular/complicaciones , Tetrodotoxina/farmacología , Ganglio del Trigémino/efectos de los fármacos , Ganglio del Trigémino/fisiopatología
12.
J Neurophysiol ; 93(3): 1585-97, 2005 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-15525813

RESUMEN

Several painful conditions, including temporomandibular disorders (TMD), are more prevalent and more severe in women than in men. Although the physiological basis for this sex difference remains to be determined, it is likely that estrogen is an underlying factor. The present study was performed to test the hypotheses that estrogen increases the excitability of rat temporomandibular joint (TMJ) afferents and exacerbates the inflammation-induced sensitization of these sensory neurons. Retrogradely labeled TMJ neurons from ovariectomized rats and ovariectomized rats receiving chronic estrogen replacement were studied using whole cell patch-clamp techniques three days after injecting the TMJ with either saline or Complete Freund's Adjuvant to induce inflammation. Excitability was assessed with depolarizing current injection to determine action potential threshold, rheobase, and the response to suprathreshold stimuli. Spontaneous activity was also assessed. Both inflammation and estrogen increased the excitability of TMJ neurons as reflected by decreases in action potential threshold and rheobase and increases in the incidence of spontaneous activity. The effects were additive with neurons from rats receiving both estrogen and inflammation being the most excitable. The increases in excitability were associated with changes in passive properties and action potential waveform, suggesting that estrogen and inflammation affect the expression and/or properties of ion channels in TMJ neurons. Importantly, the influence of estrogen on both baseline and inflammation-induced changes in TMJ neuronal excitability may help explain the profound sex difference observed in TMD as well as suggest a novel target for the treatment of this pain condition.


Asunto(s)
Estrógenos/farmacología , Inflamación/fisiopatología , Neuronas Aferentes/efectos de los fármacos , Articulación Temporomandibular/citología , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Potenciales de Acción/efectos de la radiación , Análisis de Varianza , Animales , Capsaicina/metabolismo , Capsaicina/farmacología , Carbocianinas/metabolismo , Recuento de Células/métodos , Tamaño de la Célula , Células Cultivadas , Distribución de Chi-Cuadrado , Capacidad Eléctrica , Estimulación Eléctrica/métodos , Estrógenos/sangre , Femenino , Adyuvante de Freund , Glicoproteínas/metabolismo , Inmunohistoquímica/métodos , Inflamación/inducido químicamente , Lectinas/metabolismo , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Potenciales de la Membrana/efectos de la radiación , Proteínas de Neurofilamentos/metabolismo , Neuronas Aferentes/clasificación , Neuronas Aferentes/efectos de la radiación , Ovariectomía/métodos , Técnicas de Placa-Clamp/métodos , Radioinmunoensayo/métodos , Ratas , Ratas Sprague-Dawley , Ganglio del Trigémino/citología
13.
Pain ; 109(3): 471-80, 2004 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-15157708

RESUMEN

It is generally believed that nerve injury results in neuronal hyperexcitability that reflects in part a change in Na+ currents. However, there are conflicting data on the nature of Na+ current changes and the association between alterations in Na+ currents and increases in excitability. One potential source of conflicting data is that injured and spared neurons may respond differently to nerve injury; these subpopulations of neurons have not been distinguished in previous studies with the axotomy model of nerve injury (complete transection of the sciatic nerve). The present study was performed to determine the relationship between changes in Na+ channels and changes in neuronal excitability in identified injured dorsal root ganglion neurons post-axotomy. Small (< 45 pF) neurons labeled with a DiI injection into the sciatic nerve were studied 10 days and 4 weeks post-axotomy. Ten days post-axotomy, tetrodotoxin-resistant (TTX-R) Na+ current (INa) was decreased and TTX-sensitive (TTX-S) INa was increased, however, excitability was unchanged. Four weeks post-axotomy, neurons had become hyperexcitable while TTX-R INa remained reduced and TTX-S INa had returned to control levels. Thus, axotomy-induced changes in Na+ currents were not correlated with an axotomy-induced change in excitability. Additional analysis of axotomized neurons suggested that concomitant changes in other ionic currents occurred. These results suggest that neuronal excitability following axotomy is dependent on the sum of changes in ionic currents, and the overall effect on excitability may not always correspond to that predicted by a change in a single class of voltage-gated ion channel.


Asunto(s)
Ganglios Espinales/fisiología , Conducción Nerviosa/fisiología , Neuronas Aferentes/fisiología , Traumatismos de los Nervios Periféricos , Nervios Periféricos/fisiopatología , Canales de Sodio/fisiología , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Animales , Axotomía , Carbocianinas , Membrana Celular/efectos de los fármacos , Membrana Celular/fisiología , Células Cultivadas , Ganglios Espinales/citología , Ganglios Espinales/efectos de los fármacos , Masculino , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Conducción Nerviosa/efectos de los fármacos , Neuronas Aferentes/citología , Neuronas Aferentes/efectos de los fármacos , Técnicas de Placa-Clamp , Nervios Periféricos/metabolismo , Ratas , Ratas Sprague-Dawley , Neuropatía Ciática/metabolismo , Neuropatía Ciática/fisiopatología , Bloqueadores de los Canales de Sodio/farmacología , Canales de Sodio/efectos de los fármacos , Tetrodotoxina/farmacología
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