RESUMEN
STUDY DESIGN: we investigated the localization of insulin-like growth factor 1 (IGF-1) using immunohistochemistry and the effects of small interfering RNA (siRNA) on IGF-1 in dorsal root ganglions (DRG) in a rat lumbar disc herniation (LDH) model. OBJECTIVE: to determine the localization and function of IGF-1 in DRG of an experimental model of LDH. SUMMARY OF BACKGROUND DATA: mechanical compression and chemical irritation are 2 major causative factors of radiculopathy in LDH. IGF-1, Ccnd1, Cdc2a, and CyclinA2 genes have been shown to be significantly upregulated in the mechanical model, but not in the chemical model. However, the localization and function of IGF-1 in DRG remain unknown in the mechanical compression animals. METHODS: twenty-six adult female Sprague-Dawley rats were used in this study. A mechanical compression model was prepared by inserting a stainless rod. The rod was not inserted in the sham model. Expression of IGF-1 and Neuronal Nucli (NeuN) or glial fibrillary acidic protein was determined using double-fluorescence 7 days after mechanical compression (n = 5). Rats were randomly separated into 3 groups for the siRNA study (n = 7 in each group): (1) vehicle group; (2) siRNA group; and (3) sham group. The mechanical withdrawal threshold of the plantar food pad was examined using von Frey filaments for 35 days. RESULTS: IGF-1 was localized particularly in the neuronal cell body, and revealed that it colocalized with NeuN but not with glial fibrillary acidic protein. The threshold was reduced in the vehicle and siRNA groups compared with the sham group. The threshold of the siRNA group significantly recovered from reduction compared with the vehicle group at 5 days after surgery, and this effect persisted throughout the experimental period. CONCLUSION.: IGF-1 was localized with neuronal cell bodies in DRG. IGF-1 knockdown caused a reduction in mechanical allodynia. The upregulation of IGF-1 might be a key factor in painful radiculopathy induced by mechanical factors.
Asunto(s)
Modelos Animales de Enfermedad , Ganglios Espinales/fisiopatología , Factor I del Crecimiento Similar a la Insulina/fisiología , Desplazamiento del Disco Intervertebral/fisiopatología , Animales , Antígenos Nucleares/metabolismo , Femenino , Ganglios Espinales/metabolismo , Hiperalgesia/genética , Hiperalgesia/fisiopatología , Inmunohistoquímica , Factor I del Crecimiento Similar a la Insulina/genética , Factor I del Crecimiento Similar a la Insulina/metabolismo , Desplazamiento del Disco Intervertebral/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Neuronas/metabolismo , Umbral del Dolor , Interferencia de ARN , Distribución Aleatoria , Ratas , Ratas Sprague-DawleyRESUMEN
BACKGROUND: Calcitonin is used as a treatment to reduce the blood calcium concentration in hypercalcemia and to improve bone mass in osteoporosis. An analgesic effect of calcitonin has been observed and reported in clinical situations. Ovariectomized (OVX) rats exhibit the same hormonal changes as observed in humans with osteoporosis and are an animal model of postmenopausal osteoporosis. The aim of this study to investigate antinociceptive effect of calcitonin in OVX rats using the immunohistochemical study. METHODS: We assessed the antinociceptive effects of calcitonin in an ovariectomized (OVX) rat model, which exhibit osteoporosis and hyperalgesia, using the immunohistochemical method. Fifteen rats were ovariectomized bilaterally, and ten rats were received the same surgery expected for ovariectomy as a sham model. We used five groups: the OVX-CT (n = 5), the sham-CT (n = 5), and the OVX-CT-pcpa (n = 5) groups received calcitonin (CT: 4 U/kg/day), while OVX-vehi (n = 5) and the sham-vehi (n = 5) groups received vehicle subcutaneously 5 times a week for 4 weeks. The OVX-CT-pcpa-group was given traperitoneal injection of p-chlorophenylalanine (pcpa; an inhibitor of serotonin biosynthesis) (100 mg/kg/day) in the last 3 days of calcitonin injection. Two hours after 5% formalin (0.05 ml) subcutaneously into the hind paw, the L5 spinal cord were removed and the number of Fos-immunoreactive (ir) neurons were evaluated using the Mann-Whitney-U test. RESULTS: The numbers of Fos-ir neurons in the OVX-CT and sham-CT groups were significantly less than in the OVX-vehi and sham-vehi groups, respectively (p = 0.0090, p = 0.0090). The number of Fos-ir neurons in the OVX-CT-pcpa-group was significantly more than that of the OVX-CT-group (p = 0.0283), which means pcpa inhibits calcitonin induced reduction of c-Fos production. CONCLUSION: The results in this study demonstrated that 1) the increase of c-Fos might be related to hyperalgesia in OVX-rats. 2) Calcitonin has an antinociceptive effect in both OVX and sham rats. 3) The central serotonergic system is involved in the antinociceptive properties of calcitonin.
Asunto(s)
Analgésicos/farmacología , Calcitonina/farmacología , Nociceptores/efectos de los fármacos , Analgésicos/metabolismo , Animales , Biomarcadores/análisis , Biomarcadores/metabolismo , Calcitonina/metabolismo , Sistema Nervioso Central/citología , Sistema Nervioso Central/efectos de los fármacos , Sistema Nervioso Central/metabolismo , Modelos Animales de Enfermedad , Femenino , Fenclonina/farmacología , Hiperalgesia/tratamiento farmacológico , Hiperalgesia/genética , Hiperalgesia/metabolismo , Inmunohistoquímica , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Nociceptores/fisiología , Osteoporosis/tratamiento farmacológico , Osteoporosis/genética , Osteoporosis/metabolismo , Ovariectomía , Dolor/tratamiento farmacológico , Dolor/metabolismo , Dolor/fisiopatología , Dimensión del Dolor , Umbral del Dolor/efectos de los fármacos , Umbral del Dolor/fisiología , Proteínas Proto-Oncogénicas c-fos/efectos de los fármacos , Proteínas Proto-Oncogénicas c-fos/metabolismo , Ratas , Serotonina/metabolismo , Antagonistas de la Serotonina/farmacologíaRESUMEN
STUDY DESIGN: Comprehensive overviews of gene expression changes in dorsal root ganglion (DRG) were obtained using microarrays in 2 rat models of experimental lumbar disc herniation (LDH). OBJECTIVE: To clarify the mechanisms of painful radiculopathy caused by LDH from the viewpoint of gene expression changes in DRG of 2 rat models of LDH. SUMMARY AND BACKGROUND DATA: Mechanical compression and chemical irritation are considered to be the 2 major causative factors of radiculopathy associated with LDH. Several basic studies have revealed histologic and functional changes in the nerve root and DRG induced by mechanical compression or application of nucleus pulposus. However, the effects of the 2 major factors have not been investigated in detail. METHODS.: The effects of mechanical and chemical factors were assessed in 2 models and in sham-operated rats. The mechanical compression model had a stainless steel rod inserted through a drill hole in the L5 lamina; the nucleus pulposus model had autologous nucleus pulposus placed in the drill hole, and only a drill hole was made in the L5 lamina of sham-operated rats. Samples from the left L5 DRG were harvested from the models with mechanical allodynia and from sham rats and analyzed using microarrays at 3 and 7 days after surgery. RESULTS: The gene expression profiles differed in the 2 models at 7 days, but were similar at 3 days after surgery. Expression of the growth factor gene, insulin-like growth factor 1, and of the cyclinD1, cell division cycle 2 homolog A, and cyclinA2 genes related to the cell cycle was significantly upregulated in the DRG of the mechanical compression group at 7 days after surgery. CONCLUSION: Mechanical and chemical factors caused altered gene expression in the DRG at 7 days after surgery, suggesting that the mechanisms of nerve injury induced by these factors differ. The upregulation of IGF-1 might be a key factor in painful radiculopathy induced by mechanical factors.
Asunto(s)
Modelos Animales de Enfermedad , Ganglios Espinales/fisiología , Regulación de la Expresión Génica/fisiología , Desplazamiento del Disco Intervertebral/genética , Desplazamiento del Disco Intervertebral/metabolismo , Vértebras Lumbares/fisiología , Animales , Femenino , Ganglios Espinales/patología , Perfilación de la Expresión Génica/métodos , Desplazamiento del Disco Intervertebral/patología , Vértebras Lumbares/patología , Ratas , Ratas Sprague-DawleyRESUMEN
BACKGROUND: Reduction of blood flow is important in the induction of neurogenic intermittent claudication (NIC) in lumbar spinal canal stenosis. PGE1 improves the mean walking distance in patients with NIC type cauda equina compression. PGE1 derivate might be effective in dilating blood vessels and improving blood flow in nerve roots with chronically compressed cauda equina. The aim of this study was to assess whether PGE1 derivate has vasodilatory effects on both arteries and veins in a canine model of chronic cauda equina compression. METHODS: Fourteen dogs were used in this study. A plastic balloon inflated to 10 mmHg was placed under the lamina of the 7th lumbar vertebra for 1 week. OP-1206-cyclodextrin clathrate (OP-1206-CD: prostaglandin E1 derivate) was administered orally. The blood vessels of the second or third sacral nerve root were identified using a specially designed surgical microscope equipped with a video camera. The diameter of the blood vessels was measured on video-recordings every 15 minutes until 90 minutes after the administration of the PGE1 derivate. RESULTS: We observed seven arteries and seven veins. The diameter and blood flow of the arteries was significantly increased compared with the veins at both 60 and 75 minutes after administration of the PGE1 derivate (p < 0.05). Blood flow velocity did not change over 90 minutes in either the arteries or veins. DISCUSSION: The PGE1 derivate improved blood flow in the arteries but did not induce blood stasis in the veins. Our results suggest that the PGE1 derivate might be a potential therapeutic agent, as it improved blood flow in the nerve roots in a canine model of chronic cauda equina compression.