Effect of the glucocorticoid receptor antagonist Org 34850 on basal and stress-induced corticosterone secretion

The activity of the hypothalamic-pituitary-adrenal (HPA) axis is characterised both by an ultradian pulsatile pattern of glucocorticoid secretion and an endogenous diurnal rhythm. Glucocorticoid feedback plays a major role in regulating HPA axis activity and this mechanism occurs via two different receptors: mineralocorticoid (MR) and glucocorticoid receptors (GR). In the present study, the effects of both acute and subchronic treatment with the GR antagonist Org 34850 on basal and stress-induced HPA axis activity in male rats were evaluated. To investigate the effect of Org 34850 on basal diurnal corticosterone rhythm over the 24-h cycle, an automated blood sampling system collected samples every 10 min. Acute injection of Org 34850 (10 mg/kg, s.c.) did not affect basal or stress-induced corticosterone secretion, but was able to antagonise the inhibitory effect of the glucocorticoid agonist methylprednisolone on stress-induced corticosterone secretion. However, 5 days of treatment with Org 34850 (10 mg/kg, s.c., two times a day), compared to rats treated with vehicle (5% mulgofen in 0.9% saline, 1 ml/kg, s.c.), increased corticosterone secretion over the 24-h cycle and resulted in changes in the pulsatile pattern of hormone release, but had no significant effect on adrenocorticotrophic hormone secretion or on stress-induced corticosterone secretion. Subchronic treatment with Org 34850 did not alter GR mRNA expression in the hippocampus, paraventricular nucleus of the hypothalamus or anterior-pituitary, or MR mRNA expression in the hippocampus. Our data suggest that a prolonged blockade of GRs is required to increase basal HPA axis activity. The changes observed here with ORG 34850 are consistent with inhibition of GR-mediated negative feedback of the HPA axis. In light of the evidence showing an involvement of dysfunctional HPA axis in the pathophysiology of depression, Org 34850 could be a potential treatment for mood disorders.     

Zonisamide reduces the increase in 8-hydroxy-2'-deoxyguanosine levels formed during iron-induced epileptogenesis in the brains of rats

PURPOSE: To examine the change of 8-hydroxy-2'deoxyguanosine (8-OHdG) levels, which are used as a marker for oxidative DNA damage, in iron-induced epileptogenic foci of the rat cerebrum. METHOD: Male Wistar rats were given a cortical injection of ferric chloride, and their 8-OHdG levels were determined over time. Additional animals were pretreated with the antiepileptic drug zonisamide (ZNS) before the ferric chloride injection, and their 8-OHdG levels were compared with the nonpretreated rats. RESULTS: Fifteen minutes after ferric chloride solution injection, the level of 8-OHdG increased, reaching a maximum 30 minutes after injection. Sixty minutes after injection, the levels coincided with those of controls. ZNS, in concentrations of 50 and 100 mg/kg body weight, prevented the increase of 8-OHdG levels within the cerebrum 30 minutes after iron solution injection. CONCLUSIONS: These results indicate that the formation of iron-induced epileptogenic foci in rats is related to DNA-damage-induced reactive oxygen species and that the inhibition of 8-OHdG formation by ZNS after iron injection may be due to the drug's antioxidant activity. The data suggest that free radical species known to be formed during iron salts-induced focal epileptogenesis cause damage to isocortical DNA. Furthermore, ZNS appears to inhibit the focal injuring response to DNA that occurs following iron salts-induced acute epileptogenesis.     

Simvastatin reduces caspase-3 activation and inflammatory markers induced by hypoxia-ischemia in the newborn rat

The present study was undertaken to evaluate whether in a neonatal model of stroke a prophylactic neuroprotective treatment with simvastatin modulates hypoxia-ischemia-induced inflammatory and apoptotic signaling. Procaspase-3 and cleaved caspase-3 expression showed a peak at 24 h and returned to control values after 5 days. Caspase-3 activity followed the same pattern of caspase-3 proteolytic cleavage. In simvastatin-treated ischemic animals, the expression of these proteins and caspase-3 activity were significantly lower when compared to that of ischemic animals. alpha-Spectrin and protein kinase C-alpha (PKCalpha) cleavages were not affected by the treatment. Poly (ADP-ribose) polymerase fragmentation, caspase-1 activation, and IL-1beta and ICAM-1 mRNA expression were increased by hypoxia-ischemia and significantly reduced in simvastatin-treated animals. The results indicate that simvastatin-induced attenuation of hypoxia-ischemia brain injury in the newborn rat occurs through reduction of the inflammatory response, caspase-3 activation, and apoptotic cell death.     

The phosphodiesterase type 2 inhibitor BAY 60‐7550 reverses functional impairments induced by brain ischemia by decreasing hippocampal neurodegeneration and enhancing hippocampal neuronal plasticity

Cognitive and affective impairments are the most characterized consequences following cerebral ischemia. BAY 60‐7550, a selective phosphodiesterase type 2 inhibitor (PDE2‐I), presents memory‐enhancing and anxiolytic‐like properties. The behavioral effects of BAY 60‐7550 have been associated with its ability to prevent hydrolysis of both cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) thereby interfering with neuronal plasticity. Here, we hypothesize that PDE2‐I treatment could promote functional recovery after brain ischemia. Mice C57Bl/6 were submitted to bilateral common carotid artery occlusion (BCCAO), an experimental model of transient brain ischemia, for 20 min. During 21 days after reperfusion, the animals were tested in a battery of behavioral tests including the elevated zero maze (EZM), object location task (OLT) and forced swim test (FST). The effects of BAY 60‐7550 were evaluated on neuronal nuclei (NeuN), caspase‐9, cAMP response element‐binding protein (CREB), phosphorylated CREB (pCREB) and brain‐derived neurotrophic factor (BDNF) expression in the hippocampus. BCCAO increased anxiety levels, impaired hippocampus‐dependent cognitive function and induced despair‐like behavior in mice. Hippocampal neurodegeneration was evidenced by a decrease in NeuN and increase incaspase‐9 protein levels in BCCAO mice. Ischemic mice also showed low BDNF protein levels in the hippocampus. Repeated treatment with BAY 60‐7550 attenuated the behavioral impairments induced by BCCAO in mice. Concomitantly, BAY 60‐7550 enhanced expression of pCREB and BDNF protein levels in the hippocampus of ischemic mice. The present findings suggest that chronic inhibition of PDE2 provides functional recovery in BCCAO mice possibly by augmenting hippocampal neuronal plasticity.     

Oxaprotiline enantiomers stimulate ACTH and corticosterone secretion in the rat

Summary The effect of oxaprotiline (OXA) enantiomers — of which (+)-OXA inhibits noradrenaline (NA) uptake, whereas (–)-OXA does not — on the secretion of adrenocorticotropin hormone (ACTH) and corticosterone was studied in rats. Both enantiomers dose-dependently and with a similar potency increased the plasma level of ACTH and corticosterone, the effect of (–)-OXA on corticosterone being of a longer duration. The stimulation of ACTH secretion and the inability of (+)- and (–)-OXA to increase the plasma corticosterone concentration in animals pretreated with dexamethasone indicate that secretion of the latter hormone results from the action of the enantiomers at a level superior to the adrenal cortex, i.e. the hypothalamus/pituitary.The corticosterone response to (+)- or (–)-OXA was not modified in rats with a selective lesion of NA nerve endings induced by the neurotoxin DSP-4, nor was it affected by the selective ₁-antagonist prazosin, the selective ₂-antagonist yohimbine, the mixed ₁/₂-antagonist phentolamine, the selective dopamine (D₂) receptor antagonist sulpiride and the non-selective 5-hydroxytryptamine (5-HT) receptor antagonist metergoline. These results indicate that neither the NA system nor D₂ and 5-HT receptors are involved in the hormonal response to the OXA enantiomers.Although the (+)- and (–)-OXA-induced stimulation of corticosterone secretion was not antagonized by diazepam, ipsapirone, naloxone, or propranolol, it cannot be excluded that both these enantiomers act as non-specific Stressors.     

Regulation of beta-nerve growth factor expression by inflammatory mediators in hippocampal cultures

Substances which regulate expression of nerve growth factor (NGF) were examined in embryonic rat hippocampal cultures containing both neurons and glial cells. Both cell types expressed NGF mRNA when cultivated in vitro. Lipopolysaccharide, an activator of macrophages, elicited a significant increase in NGF mRNA. Interleukin-1 beta evoked a similar increase in NGF mRNA which was accompanied by a rise in NGF protein. The Il-1-induced increase was partially blocked by indomethacin, suggesting that prostaglandins might mediate this effect. Treatment of the cultures directly with prostaglandin E2 resulted in elevated levels of both NGF mRNA and protein. Thus, agents which promote inflammatory activity appear to increase NGF expression. Moreover, a suppressor of inflammation, dexamethasone, decreased NGF expression. Our observations indicate that a variety of immunomodulators regulate NGF expression in the hippocampus.     

Persistent behavioral impairments and neuroinflammation following global ischemia in the rat

Cognitive deficits associated with cardiac arrest have been well documented; however, the corresponding deficits in animal models of global ischemia have not been comprehensively assessed, particularly after long‐term, clinically relevant survival times. We exposed male Sprague–Dawley rats to 10 min of bilateral carotid artery occlusion + systemic hypotension (40–45 mmHg) or sham surgery, and used histopathological assessments for short‐term survival animals (16 days) and both behavioral and histopathological assessments for long‐term survival animals (270 days). Analyses revealed significant long‐term deficits in ischemic animals’ learning, memory (T‐maze, radial arm maze), working memory (radial arm maze), and reference memory (Morris water maze, radial arm maze) abilities that were not associated with a general cognitive decline. Histological results showed significant increases in glial fibrillary acidic protein, neuron glia 2, OX‐42 and ED‐1 staining, as well as significant decreases in microtubule‐associated protein 2 staining and cornu ammonis area 1 (CA1) cell counts 16 days post‐ischemia. The pattern at 270 days was similar, but notably there was a persistent elevation of ED‐1 staining, suggesting recent cell death as well as significant atrophy of CA1. Whereas previous work has primarily reported transient changes in behavior after global ischemia, this study describes disturbances in several different functional domains following CA1 cell loss at clinically relevant survival times. Moreover, the histopathological outcome is suggestive of a spontaneous repopulation of CA1, but this was not sufficient to offset the behavioral impairments arising from the ischemic insult.     

Pre-operative inflammatory markers and the risk of postoperative delirium in elderly patients

OBJECTIVE: Pathophysiological mechanisms leading to delirium are not clear. Age is a known risk factor and hypothesised to be accompanied by a low-grade inflammatory state. Previous studies have shown an association between delirium and circulating proinflammatory markers in acutely ill and postoperative patients. In light of the ageing/inflammation theory, we investigated the association of these markers with delirium in not acutely ill, elderly patients. METHODS: In a prospective nested case-control study levels of C-reactive protein (CRP), interleukin 6 (Il-6), insulin growth factor 1 (IGF-1) were measured pre-operatively in elderly patients admitted for hip-surgery. These levels were compared between patients who later developed a post-operative delirium and patients who did not. Patients were matched for age and disease severity. RESULTS: Eighteen patients who developed delirium post-operatively were matched with 50 controls. Median APACHE-scores were below 16 in both groups. Pre-operative serum concentrations of CRP, Il-6 and IGF-1 did not differ between groups. IL-6 levels were associated with a measure of cognitive impairment. CONCLUSION: In the present study no relationship was found between levels of pre-operative circulating pro-inflammatory markers and post-operative delirium in elderly patients, who were free from acute or severe disease. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Loss of the atypical inflammatory response in juvenile and aged rats

Epidemiological evidence indicates that the severity of many human neuropathologies is often age-related, and this also appears true in rodent models of human disease. In this study, we examined the inflammatory response within the brain to the archetypal pro-inflammatory cytokines interleukin-1beta (IL-1beta) or tumour necrosis factor-alpha (TNF-alpha). We assessed how the cerebral vasculature changes with age and whether any structural alterations are associated with altered cytokine sensitivities. Six hours after equivalent microinjections of IL-1beta or TNF-alpha, 3-week-old juvenile and 18-month-old aged rats displayed increased leucocyte recruitment, blood-brain barrier (BBB) breakdown, and a loss of specificity in the populations of leucocytes recruited when compared with the restricted profile observed in 2-month-old young adult rat brain. The expression of the tight junction protein claudin-1 was absent in those vessels where neutrophils were being actively recruited. To determine whether changes in the structure of the BBB might be responsible for the increased susceptibility observed at either end of the age spectrum, we compared the number of claudin-1 positive vessels in the unchallenged brain to the total number of vessels. Virtually all vessels in the young adult brain express claudin-1, but a significant proportion of vessels are claudin-1 negative in the juvenile rat brain. In the aged rat brain, the overall number of vessels is markedly reduced, but the majority of these still appear to be claudin-1 positive. The pattern of claudin-1 expression together with the change in vessel density indicates that the properties of the BBB change with age, and, despite similarities, the underlying cause of the heightened inflammatory response in the juvenile and in the aged brain is likely to differ. Indeed, the spatial characteristics of the cytokine-induced BBB breakdown are different at either end of the age spectrum. These studies identify two periods within the lifespan of a rat where susceptibility to pro-inflammatory mediators is dramatically increased.     

Inhibition of phospholipase A2 activity reduces membrane fluidity in rat hippocampus

Summary. Phospholipase A₂ (PLA₂) is a family of key enzymes in membrane phospholipid metabolism. In rats, the inhibition of PLA₂ activity in the hippocampus was found to impair memory formation. Because memory function is largely dependent on the fluidity of brain membranes, we performed the present study to investigate the effects of in vivo PLA₂ inhibition (with PACOCF₃) on the fluidity of hippocampal membranes from rats trained in a learning task. Hippocampal tissue from rats injected with 100µM PACOCF₃ showed reduced membrane fluidity as compared to vehicle (p<0.01), and the reduction of membrane fluidity was highly correlated with PLA₂ inhibition (r=.76, p<0.03). This finding is of interest because reduction of brain membrane fluidity impairs memory formation and both decreased PLA₂ activity and reduced membrane fluidity have been reported in the brain from patients with Alzheimers disease.     

Minocycline protects the blood-brain barrier and reduces edema following intracerebral hemorrhage in the rat

Intracerebral hemorrhage (ICH) results from rupture of a blood vessel in the brain. After ICH, the blood–brain barrier (BBB) surrounding the hematoma is disrupted, leading to cerebral edema. In both animals and humans, edema coincides with inflammation, which is characterized by production of pro-inflammatory cytokines, activation of resident brain microglia and migration of peripheral immune cells into the brain. Accordingly, inflammation is an attractive target for reducing edema following ICH. In the present study, BBB damage was assessed by quantifying intact microvessels surrounding the hematoma, monitoring extravasation of IgG and measuring brain water content 3 days after ICH induced by collagenase injection into the rat striatum. In the injured brain, the water content increased in both ipsilateral and contralateral hemispheres compared with the normal brain. Quantitative real-time RT-PCR revealed an up-regulation of inflammatory genes associated with BBB damage; IL1β, TNFα and most notably, MMP-12. Immunostaining showed MMP-12 in damaged microvessels and their subsequent loss from tissue surrounding the hematoma. MMP-12 was also observed for the first time in neurons. Dual-antibody labeling demonstrated that neutrophils were the predominant source of TNFα protein. Intraperitoneal injection of the tetracycline derivative, minocycline, beginning 6 h after ICH ameliorated the damage by reducing microvessel loss, extravasation of plasma proteins and edema; decreasing TNFα and MMP-12 expression; and reducing the numbers of TNFα-positive cells and neutrophils in the brain. Thus, minocycline, administered at a clinically relevant time, appears to target the inflammatory processes involved in edema development after ICH.     

Prolonged corticosterone exposure induces dendritic spine remodeling and attrition in the rat medial prefrontal cortex

The stress‐responsive hypothalamo–pituitary–adrenal (HPA) axis plays a central role in promoting adaptations acutely, whereas adverse effects on physiology and behavior following chronic challenges may result from overactivity of this system. Elevations in glucocorticoids, the end‐products of HPA activation, play roles in adaptive and maladaptive processes by targeting cognate receptors throughout neurons in limbic cortical networks to alter synaptic functioning. Because previous work has shown that chronic stress leads to functionally relevant regressive alterations in dendritic spine shape and number in pyramidal neurons in the medial prefrontal cortex (mPFC), this study examines the capacity of sustained increases in circulating corticosterone (B) alone to alter dendritic spine morphology and density in this region. Subcutaneous B pellets were implanted in rats to provide continuous exposure to levels approximating the circadian mean or peak of the steroid for 1, 2, or 3 weeks. Pyramidal neurons in the prelimbic area of the mPFC were selected for intracellular fluorescent dye filling, followed by high‐resolution three‐dimensional imaging and analysis of dendritic arborization and spine morphometry. Two or more weeks of B exposure decreased dendritic spine volume in the mPFC, whereas higher dose exposure of the steroid resulted in apical dendritic retraction and spine loss in the same cell population, with thin spine subtypes showing the greatest degree of attrition. Finally, these structural alterations were noted to persist following a 3‐week washout period and corresponding restoration of circadian HPA rhythmicity. These studies suggest that prolonged disruptions in adrenocortical functioning may be sufficient to induce enduring regressive structural and functional alterations in the mPFC. J. Comp. Neurol. 524:3729–3746, 2016. © 2016 Wiley Periodicals, Inc.     

Effects of chronic corticosterone treatment on electrophysiological and behavioral measures in the rat

The electrophysiological and behavioral effects of daily oral exposure to acorticosterone or vehicle solution was evaluated in 20 male Wistar rats over a 10-wk period. Evaluation of the rats' behavior in an open field apparatus, as well as in automated locomotor cages, revealed no significant differences between steroid-treated and control animals following 5–6 wk of exposure. No differences in mean EEG power, as estimated by spectral analysis of cortical and dorsal hippocampal recordings, were observed between the two groups following 8 wk of exposure. However, some increases in EEG “stability” were noted in the corticosterone-treated rats. At 9 wk, responses to auditory stimuli, as assessed by evoked responses, in cortex and dorsal hippocampus were also found to be unaltered by corticosterone exposure. These studies suggest that exposure to daily oral corticosterone, in the doses used, over a period of 2–3 mo is not associated with gross electrophysiological or spontaneos behavioral effects in the brain areas assessed.     

Sequential expression of cyclooxygenase-2, glutamate receptor-2, and platelet activating factor receptor in rat hippocampal neurons after fluid percussion injury

Traumatic brain injury causes gene expression changes in different brain regions. Occurrence and development of traumatic brain injury are closely related, involving expression of three factors, namely cyclooxygenase-2, glutamate receptor-2, and platelet activating factor receptor. However, little is known about the correlation of these three factors and brain neuronal injury. In this study, primary cultured rat hippocampal neurons were subjected to fluid percussion injury according to Scott’s method, with some modifications. RT-PCR and semi-quantitative immunocytochemical staining was used to measure the expression levels of cyclooxygenase-2, glutamate receptor-2, and platelet activating factor receptor. Our results found that cyclooxygenase-2 expression were firstly increased post-injury, and then decreased. Both mRNA and protein expression levels reached peaks at 8 and 12 hours post-injury, respectively. Similar sequential changes in glutamate receptor 2 were observed, with highest levels mRNA and protein expression at 8 and 12 hours post-injury respectively. On the contrary, the expressions of platelet activating factor receptor were firstly decreased post-injury, and then increased. Both mRNA and protein expression levels reached the lowest levels at 8 and 12 hours post-injury, respectively. Totally, our findings suggest that these three factors are involved in occurrence and development of hippocampal neuronal injury.     

Sub-concussive brain injury in the Long-Evans rat induces acute neuroinflammation in the absence of behavioral impairments

Sub-concussive brain injuries may result in neurophysiological changes, cumulative effects, and neurodegeneration. The current study investigated the effects of a mild lateral fluid percussion injury (0.50-0.99 atm) on rat behavior and neuropathology to address the need to better understand sub-concussive brain injury. Male Long-Evans rats received either a single mild lateral fluid percussion injury or a sham-injury, followed by either a short (24 h) or long (4 weeks) recovery period. After recovery, rats underwent extensive behavioral testing consisting of tasks for rodent cognition, anxiety- and depression-like behaviors, social behavior, and sensorimotor function. At the completion of behavioral testing rats were sacrificed and brains were examined immunohistochemically with markers for neuroinflammation and axonal injury. No significant group differences were found on behavioral and axonal injury measures. However, rats given one mild fluid percussion injury displayed an acute neuroinflammatory response, consisting of increased microglia/macrophages and reactive astrogliosis, at 4 days post-injury. Neuroinflammation is a mechanism with the potential to contribute to the cumulative and neurodegenerative effects of repeated sub-concussive injuries. The current findings are consistent with findings in humans experiencing a sub-concussive blow, and provide support for the use of mild lateral fluid percussion injury in the rat as a model of sub-concussive brain injury.     

Inhibition of GABA uptake in the rat hippocampal slice

Pharmacological manipulations known to inhibit GABA uptake prolonged GABA-evoked conductance increases in CA1 pyramidal cells in the rat hippocampal slice preparation. Treatments included reduction of extracellular sodium and exposure to cis-4-OH-nipecotic acid, nipecotic acid or L-2,4-diaminobutyric acid (all at 1 mM). These effects contrast with the results obtained with 4-OH-isonipecotic acid, an inactive structural analog of nipecotic acid, which had no effect on the time-course of GABA responses. 4,5,6,7-Tetrahydroisoxazolo[4,5-c]pyridine-3-ol (THPO), an impotent but selective inhibitor of GABA uptake into glia, did not prolong GABA-evoked responses. The effect of sodium reduction depended on the distance between the source of GABA and its receptors, as predicted for an uptake-limited response. GABA-receptor agonists that are poor substrates for GABA uptake (muscimol, thiomuscimol, piperidine-4-sulphonic acid, isoguvacine and 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-3-ol (THIP) evoked very long conductance changes that were not further prolonged by uptake inhibitors. These results demonstrate the presence of a functional GABA uptake system in the hippocampal slice. The accessibility of hippocampal GABAergic synapses and the known susceptibility of the hippocampus to epileptiform events suggest that the hippocampal slice could be a valuable CNS preparation to study the role of GABA uptake in synaptic physiology.     

pSTAT1, pSTAT3, and T-bet as markers of disease activity in chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is considered an auto-immune disorder. We evaluated expression of pSTAT1, T-bet, and pSTAT3 in circulating T-cells, B-cells, and monocytes and spontaneous production of interleukin-17 (IL17), interferon-gamma (IFNγ), and interleukin-10 (IL10) by peripheral blood mononuclear cells (PBMCs) from 14 active CIDP patients compared with 6 patients with long-lasting remission and 20 controls. Active disease patients showed higher pSTAT1, T-bet, and pSTAT3 in CD4⁺ T-cells than controls (p < 0.001, p = 0.0002, p = 0.0097, respectively) and remission patients (p < 0.001, p = 0.0036, p = 0.0008, respectively). pSTAT1, T-bet, and pSTAT3 were also higher in monocytes from active CIDP patients than controls (p = 0.0011, p = 0.0041, p = 0.0413, respectively) and remission patients (p = 0.0073, p = 0.0274, p = 0.0251, respectively). Moreover in CD8⁺ T-cells, pSTAT3 expression was higher in active CIDP patients than in remission patients (p = 0.0345) and in controls (p = 0.0023). IL17 and IFNγ production were significantly higher in active CIDP patients than in controls (p < 0.0395, p = 0.0010, respectively); IFNγ levels were higher also in remission CIDP patients (p = 0.0073). IL10 levels were higher in active phase patients than in controls (p = 0.0334). Our data suggest that pSTAT1, T-bet, and pSTAT3 can be considered putative markers of disease activity and potential targets for specific therapies.     

Protective effects of geraniol (a monoterpene) in a diabetic neuropathy rat model: Attenuation of behavioral impairments and biochemical perturbations

Involvement of oxidative stress, inflammatory response, and mitochondrial dysfunction in the development of diabetic neuropathy (DN) is well appreciated. The present study examines the potential of geraniol (GE), a well‐known phytoconstituent commonly found in lemon, spices, rose oil, etc., to attenuate DN‐associated oxidative/nitrosative stress by employing a streptozotocin (STZ) diabetic rat model. STZ‐induced diabetic rats provided with oral supplements of GE (100 mg/kg bw/day, 8 weeks) exhibited significant improvement in tail‐flick latency (sensory function) and the narrow beam test (motor function). Terminally, elevated levels of oxidative markers (reactive oxygen species, malondialdehyde, hydroperoxides) in cytosol of the sciatic nerve (SN) and in selected regions of the brain of diabetic rats were markedly reduced by GE supplements. Furthermore, GE significantly diminished the levels of protein carbonyls (a measure of protein oxidation) and nitrites in diabetic rats. In addition, in mitochondria, GE supplements restored the activities of enzymes, such as complexes I–III, succinate dehydrogenase, and citrate synthase, in brain regions of diabetic rats, with a concomitant reduction in the levels of oxidative markers. GE significantly lowered the enhanced cytosolic calcium levels and acetylcholinesterase activity in the SN and the brain regions of diabetic rats. Depleted dopamine levels evident in the SN and the cortex/striatum among diabetic rats were restored by GE. From our data, we hypothesize that GE may be a promising therapeutic candidate in the management of DN in humans. Further understanding of the molecular mechanisms of its neuromodulatory effects is essential in order to exploit its therapeutic efficacy. © 2014 Wiley Periodicals, Inc.