Root Ganglia Of Diabetic Rats Research Articles

Effect of Nano-eugenol and Aerobic Exercise Against the Streptozotocin Toxicity and Inflammatory Mediators P38-MAPK, NPY, and A-Rα2A in the Dorsal Root Ganglia of Diabetic Rats

Background: The aim of this study was to investigate the effects of nano-eugenol combined with aerobic exercise against the streptozotocin toxicity and inflammatory mediators P38-MAPK, NPY and A-Rα2A in the dorsal root ganglia of diabetic rats. Methods: Twenty-five, 8-week-old Wistar male rats were divided into 5 groups: 1) normal control group (normal model); 2) diabetic control group (diabetic model); 3), diabetic + exercise group (diabetic+exercise model); 4) diabetic group + nano-eugenol (diabetic+nano model); and 5) diabetic + exercise + nano-eugenol (diabetic+exercise+nano model). Diabetes was induced in the experimental groups 2 through 5 by the intraperitoneal injection of streptozotocin at 4mg/100 grams of the rats’ body weight. The nano-eugenol supplement was also gavaged into the supplement groups 4 and 5 only. Groups 3 and 5 exercised progressively at a speed of 8 to 20 meter/min for 5 to 30 min, five days a week over the 8-week study duration. Results: The diabetic rats that exercised and were treated with the nano-eugenol, showed a significant decrease in P38-MAPK gene expression compared to the normal model group (P=0.001). The study of the therapeutic modalities also showed that only the diabetic + exercise + nano-eugenol group showed a significant increase in NPY and A-Rα2A genes compared to the normal model (P=0.001). Conclusion: Based on the results, the use of nano-eugenol supplementation combined with aerobic exercise is likely to be effective in controlling the neurological damages due to diabetes by negatively regulating the P38-MAPK gene while positively regulating the NPY and A-Rα2A genes in the DRG region.

Efficacy-Based Perspective to Overcome Reduced Opioid Analgesia of Advanced Painful Diabetic Neuropathy in Rats.

Reduction of the opioid analgesia in diabetic neuropathic pain (DNP) results from μ-opioid receptor (MOR) reserve reduction. Herein, we examined the antinociceptive and antiallodynic actions of a novel opioid agonist 14-O-methymorphine-6-O-sulfate (14-O-MeM6SU), fentanyl and morphine in rats with streptozocin-evoked DNP of 9–12 weeks following their systemic administration. The antinociceptive dose-response curve of morphine but not of 14-O-MeM6SU or fentanyl showed a significant right-shift in diabetic compared to non-diabetic rats. Only 14-O-MeM6SU produced antiallodynic effects in doses matching antinociceptive doses obtained in non-diabetic rats. Co-administered naloxone methiodide (NAL-M), a peripherally acting opioid receptor antagonist failed to alter the antiallodynic effect of test compounds, indicating the contribution of central opioid receptors. Reduction in spinal MOR binding sites and loss in MOR immunoreactivity of nerve terminals in the spinal cord and dorsal root ganglia in diabetic rats were observed. G-protein coupling assay revealed low efficacy character for morphine and high efficacy character for 14-O-MeM6SU or fentanyl at spinal or supraspinal levels (Emax values). Furthermore, at the spinal level only 14-O-MeM6SU showed equal efficacy in G-protein activation in tissues of diabetic- and non-diabetic animals. Altogether, the reduction of spinal opioid receptors concomitant with reduced analgesic effect of morphine may be circumvented by using high efficacy opioids, which provide superior analgesia over morphine. In conclusion, the reduction in the analgesic action of opioids in DNP might be a consequence of MOR reduction, particularly in the spinal cord. Therefore, developing opioids of high efficacy might provide analgesia exceeding that of currently available opioids.

Effects of Chinese Medicinal Compound Jinmaitong on the Expression of Nitrotyrosine andNerve Growth Factor in the Dorsal Root Ganglia of Diabetic Rats.

Objective To study the effects of Chinese medicinal compound Jinmaitong(JMT) on the expressions of nitrotyrosine (NT) and nerve growth factor (NGF) in dorsal root ganglia of diabetic rats. Methods Experimental rat diabetic models were established by the intraperitoneal injection of streptozotocin. Rat models were then randomly divided into four groups including normal control group (Con group),diabetes mellitus group (DM group),Jinmaitong group(JMT group)(treated with JMT similar to the fifteen-fold dose of adult recommended dosage),and taurine group(Tau group)(treated with Taurine similar to the fifteen-fold dose of adult recommended dosage),with 10 rats in each group. The Con and DM groups were treated with distilled water at a daily dose of 1 ml/100 g. All rats were given intragastric administration for 16 weeks and then killed. Body weight and blood glucose were detected before and at the 4th,8th,12th,and 16th week after treatment. The pain threshold to mechanical stimulation with von Frey filament were carried out before death. The expressions of NT and NGF in dorsal root ganglion were detected by immunohistochemistry and Western blot analysis,respectively. Results Immunohistochemistry showed that the average optical density (AOD) of NT expression in DM group were significantly higher than those in control group (P=0.000),and the AOD of NGF was significantly lower than the control group (P=0.006).The AOD of NT(P=0.000,P=0.000) in both treatment groups decreased significantly and the AOD of NGF(P=0.000, P=0.004)significantly increased compared with DM group. The AOD of NT in JMT group was significantly lower than Tau group (P=0.004). Western blot analysis showed that the protein level of NT in DM group was significantly higher than that in control group (P=0.000),and the protein level of NGF was significantly lower than that in control group (P=0.000). Compared with the DM group,the protein level of NT in both treatment groups significantly decreased (P=0.001,P=0.000),and the protein level of NGF increased significantly (P=0.000,P=0.001). Conclusion Traditional Chinese medicine JMT can obviously up-regulate the expressions of NGF and reduce the NT levels in dorsal root ganglia of diabetic rats.

Expression of calcium/calmodulin-dependent protein kinase II in dorsal root ganglia in diabetic rats 6 months and 1 year after diabetes induction

Abstract Aim The aim of this study was to compare expression of total calcium/calmodulin-dependent protein kinase II (tCaMKII) and its α, β, γ and δ isoforms in dorsal root ganglion (DRG) in rat models of diabetes mellitus type I (DM1), 6 months and 1 year after diabetes induction. Methods A total of 45 male Sprague-Dawley rats weighing 160-200 g were assigned into four experimental groups: 6-months DM1 and its control group, 1-year and its control group. For the induction of DM1, after overnight fasting animals were injected intraperitonealy with 55 mg/kg of the streptozotocine (STZ). Rats were sacrificed 6 months and 1 year after the diabetes induction. The L4 and L5 ganglions were removed, fixed, embedded in freezing medium and sectioned on a cryostat. Immunofluorescence analysis was performed for detection of tCaMKII and its α, β, γ and δ isoforms. Image J software was used for analysis of immunofluorescence. Results The diabetes was successfully induced as confirmed by measurement of glucose levels and weight increase. Analysis of tCaMKII expression in DRGs revealed no differences between DM1 and control animals after 6 and 12 months. In diabetic animals, the expression of α and β isoforms decreased significantly after 6 months, compared to the controls, while decrease of γ and δ was observed after one year of diabetes in diabetic animals. Conclusions The observed changes in the expression of CaMKII isoforms reveal plastic changes of this enzyme during the chronic diabetic state and may be involved in the chronic neuropathic pain development.

Treadmill training increases the size of A cells from the L5 dorsal root ganglia in diabetic rats

The aim of this study was to evaluate the effects of physical training on the L5 dorsal root ganglion (DRG) cells in streptozotocin diabetic rats. Male adult rats were divided into 3 groups: (control, diabetic and trained diabetic). Treadmill training was performed for 10 weeks (5 days/week, twice a day). Blood glucose concentrations and body weight were evaluated 48h after diabetes induction and every 30 days thereafter. Then, animals were killed and the right L5 DRG removed. Histological and morphometric analysis consisted of evaluating nuclear and cellular volumes and areas in A and B cells at light and ultrastructural levels. Blood glucose concentrations were higher in both diabetic groups vs controls at all periods. Body weights were lower in all diabetics vs controls at all periods after diabetes induction, with a significant time vs group interaction. In A cells, the cellular and nuclear volumes were lower than control animals only in the diabetic group; control and trained diabetic animals did not differ; in B cells the cellular and nuclear volumes were lower in diabetic and trained diabetic rats. The cellular areas of A cells were smaller in diabetic rats than in control and trained diabetic rats, while the cellular areas of B cells were smaller in the diabetic and trained groups. In conclusion, treadmill training was able to increase the size of A cells from the DRG in diabetic rats and improved the morphological features of these cells.

Protein kinase Cbeta selective inhibitor LY333531 attenuates diabetic hyperalgesia through ameliorating cGMP level of dorsal root ganglion neurons.

Streptozocin (STZ)-induced diabetic rats show hyperalgesia that is partially attributed to altered protein kinase C (PKC) activity. Both attenuated neuronal nitric oxide synthase (nNOS)-cGMP system and tetrodotoxin-resistant (TTX-R) Na channels in dorsal root ganglion neurons may be involved in diabetic hyperalgesia. We examined whether PKCbeta inhibition ameliorates diabetic hyperalgesia and, if so, whether the effect is obtained through action on neurons by testing nociceptive threshold in normal and STZ-induced diabetic rats treated with or without PKCbeta-selective inhibitor LY333531 (LY) and by assessing the implication of LY in either nNOS-cGMP system or TTX-R Na channels of isolated dorsal root ganglion neurons. The decreased nociceptive threshold in diabetic rats was improved either after 4 weeks of LY treatment or with a single intradermal injection into the footpads. The treatment of LY for 6 weeks significantly decreased p-PKCbeta and ameliorated a decrease in cGMP content in dorsal root ganglia of diabetic rats. The latter effect was confirmed in ex vivo condition. The treatment with NO donor for 4 weeks also normalized both diabetic hyperalgesia and decreased cGMP content in dorsal root ganglions. The expressions of nNOS and TTX-R Na channels were not changed with LY treatment. These results suggest that LY is effective for treating diabetic hyperalgesia through ameliorating the decrease in the nNOS-cGMP system.

Stereological study of the cells of dorsal root ganglia in male diabetic rats.

Most research on diabetes mellitus has focused on physiological and biochemical aspects of the peripheral nervous system, whilst little work has been done on morphological changes of the neurons. In the present study the effects of diabetes mellitus on cervical and lumbar dorsal root ganglia (C7 and L5) were investigated using modern stereological methods. Twelve adult male Sprague-Dawley rats were randomly divided into two groups. Each group contained six male rats. Diabetes was induced in the experimental group by intraperitoneal injection of 50 mg/kg streptozotocin. At the end of 6 weeks, the rats were fixed by whole body perfusion transcardially with a buffered formalin solution. The seventh cervical and fifth lumbar dorsal root ganglia were removed and immersed in buffered formalin. After tissue processing, the ganglia were embedded in cylindrical paraffin blocks. Isotropic uniform random sections were obtained using the orientator method. Sections (5 microm thick) were selected and stained with Heidenhain's azan. Volume of perikarya of A- and B-cells and their nuclei was estimated using the nucleator method. Before estimating the mean volume, the cells were sampled using the physical disector and point sampling method. Measurements showed that mean perikaryal and nuclear volume of A- and B-cells of dorsal root ganglia (C7 and L5) was reduced in diabetic rats (p<0.05). B-cell mean perikaryal volume in diabetic rats and A- and B-cell mean nuclear volume were reduced by 66% on average. The mean volume of A-cell perikarya was affected less than the others (average 33%). In addition, the difference between the perikaryal and nuclear volume of the seventh cervical and fifth lumbar dorsal root ganglia was not statistically significant. The present study, using stereological techniques, demonstrates reduced perikaryal and nuclear volume of the seventh cervical and fifth lumbar dorsal root ganglia in diabetic rats.

Role of neurotrophins in diabetic neuropathy and treatment with nerve growth factors.

In rodent models of diabetes, there are expression deficits in nerve growth factor (NGF) and in mRNA for its high-affinity receptor, trkA, leading to decreased retrograde axonal transport of NGF and decreased support of NGF-dependent sensory neurons, with reduced expression of their neuropeptides, substance P and calcitonin gene-related peptide (CGRP). Treatment of diabetic rats with intensive insulin normalized these deficits, and treatment with exogenous NGF caused dose-related increases, giving levels of NGF and neuropeptides that were greater than those of controls. Neurotrophin-3 (NT-3) mRNA was also deficient in leg muscle from diabetic rats, and administration of recombinant NT-3 to diabetic rats increased the conduction velocity of sensory nerves without affecting motor conduction velocity. In regenerating nerves after experimental crush injury, expression of NGF in the nerve trunk is increased in diabetes to a greater extent than in controls, but this is offset by a greater reduction in the neuronal expression of trkA in dorsal root ganglia of diabetic rats. Nonetheless, targeted administration of exogenous NGF via impregnated conduits stimulated regeneration in both control and diabetic rats. These findings implicate deficient neurotrophic support in diabetic neuropathy and suggest that its correction should be a paramount therapeutic target.

Glucose and leucine uptake by rat dorsal root ganglia is not insulin sensitive

Dorsal root ganglia from rats were incubated with 3-O- methyl-[ 14 C]glucose , and [ 3H]leucine in the presence or absence of insulin in order to determine whether insulin influences the uptake of glucose and amino acids by the cells of the ganglion. No effect was detected. A significant proportion (38%) of the uptake of [ 3H]leucine was shown to be inhibited by ouabain and therefore energy dependent, utilizing Na +K +-ATPase. The activity of this enzyme is known to be impaired in dorsal root ganglia in diabetic rats, as is the uptake of amino acids; these phenomena are therefore unlikely to be due to a direct effect of reduced circulating insulin levels. The relevance of these findings to theories as to the causation of diabetic neuropathy is discussed.

Axonal transport of substance P-like immunoreactivity in ganglioside-treated diabetic rats

This study examined the effect of treatment of control and streptozotocin-diabetic rats with a mixture of gangliosides, derived from bovine brain, on parameters of axonal transport of substance P-like immunoreactivity (SPLI) and its levels in sciatic nerve and lumbar spinal ganglia. Rats were treated daily (10 mg/kg i.p.) for 28 days and compared with untreated control and diabetic groups. The duration of diabetes was 28 days in both cases. Untreated diabetic rats showed deficits in accumulation of axonally transported SPLI proximal (59% of controls) and distal (34% of controls) to sciatic nerve ligations (left in place for 12 h). Rates of accumulation were unaltered by diabetes. There were small numerical reductions in the SPLI content of unconstricted sciatic nerve and of L 4 and L 5 dorsal root ganglia in diabetic rats. None of these diabetes-associated changes was altered by ganglioside treatment, nor was there any indication of an effect of gangliosides on substance P in non-diabetic rats. The implications are discussed in relation to the possible pathogenesis of diabetic neuropathy.