Injection Of Glutamate Research Articles

Physical exercise associated with vitamin D chronic supplementation reduces kidney injury induced by monosodium glutamate.

The aim was to evaluate the effects of chronic vitamin D (VD) supplementation associated with regular swimming over renal histomorphometric aspects in obese rats. Thirty Wistar male rats (5 days old) were used. Twenty four rats were given subcutaneous injections of monosodium glutamate (MSG; 4 g/kg), and six control rats were given an equimolar saline solution. At 21-days-old, the MSG-treated rats were randomly distributed among sedentary animals (S) and exercised (E, swimming; 3x/week). These groups were subdivided into groups orally supplemented with VD (12 μg/kg; 3x/week) or not supplemented (NS), totaling Five experimental groups (n = 6 rats/group): MSG, MSG-SVD, MSG-ENS, MSG-EVD and control groups. In MSG-obese rats, there was such as a decrease in the diameter of the, glomerular tuft, Bowman's capsule, Bowman's space areas, and renal cortical thickness, compared to the control group. In MSG-SVD, MSG-ENS, and MSG-EVD animals, there was an increase in the cortical thickness in relation to the MSG group. In MSG-ENS and MSG-EVD animals, there was a reduction of tubular degeneration in relation to the MSG group. We conclude that physical exercise associated with Vitamin D supplementation can prevent of renal injury, increasing the thickness of the renal cortex and decrease the tubular degeneration.

DUODENAL-JEJUNAL BYPASS REDUCES LIPID ACCUMULATION IN THE BROWN ADIPOSE TISSUE OF HYPOTHALAMIC OBESE RATS.

ABSTRACT Background: Thermogenic activity in the brown adipose tissue (BAT) of obese individuals is reduced, and this condition may be modified by bariatric surgery (BS). Aim: To characterize fat deposition in BAT from hypothalamic obese (HyO) rats submitted to duodenal-jejunal-bypass (DJB) surgery. Methods: For induction of hypothalamic obesity, newborn male Wistar rats were treated with subcutaneous injections of monosodium glutamate (MSG). The control (CTL) group received saline solution. At 90 days, the HyO rats were submitted to DJB or sham operation, generating the HyO-DJB and HyO-SHAM groups. At 270 days, the rats were euthanized, and the BAT was weighed and submitted to histological analysis. Results: Compared to BAT from CTL animals, the BAT from HyO-SHAM rats displayed increased weight, hypertrophy with greater lipid accumulation and a reduction in nucleus number. DJB effectively increased nucleus number and normalized lipid deposition in the BAT of HyO-SHAM rats, similar to that observed in CTL animals. Conclusion: DJB surgery avoided excessive lipid deposition in the BAT of hypothalamic obese rats, suggesting that this procedure could reactivate thermogenesis in BAT, and contribute to increase energy expenditure.

Selective mGluR1 Negative Allosteric Modulator Reduces Blood-Brain Barrier Permeability and Cerebral Edema After Experimental Subarachnoid Hemorrhage.

The blood-brain barrier (BBB) disruption leads to the vasogenic brain edema and contributes to the early brain injury (EBI) after subarachnoid hemorrhage (SAH). However, the mechanisms underlying the BBB damage following SAH are poorly understood. Here we reported that the neurotransmitter glutamate of cerebrospinal fluid (CSF) was dramatically increased in SAH patients with symptoms of cerebral edema. Using the rat SAH model, we found that SAH caused the increase of CSF glutamate level and BBB permeability in EBI, intracerebroventricular injection of exogenous glutamate deteriorated BBB damage and cerebral edema, while intraperitoneally injection of metabotropic glutamate receptor 1(mGluR1) negative allosteric modulator JNJ16259685 significantly attenuated SAH-induced BBB damage and cerebral edema. In an in vitro BBB model, we showed that glutamate increased monolayer permeability of human brain microvascular endothelial cells (HBMEC), whereas JNJ16259685 preserved glutamate-damaged BBB integrity in HBMEC. Mechanically, glutamate downregulated the level and phosphorylation of vasodilator-stimulated phosphoprotein (VASP), decreased the tight junction protein occludin, and increased AQP4 expression at 72h after SAH. However, JNJ16259685 significantly increased VASP, p-VASP, and occludin, and reduced AQP level at 72h after SAH. Altogether, our results suggest an important role of glutamate in disruption of BBB function and inhibition of mGluR1 with JNJ16259685 reduced BBB damage and cerebral edema after SAH.

Effects and mechanism of injection of glutamate into hypothalamic paraventricular nucleus on visceral pain in chronic visceral hypersensitivity rats

Objective To investigate the effects of glutamate (Glu) injected into hypothalamic paraventricular nucleus (PVN) on visceral pain of chronic visceral hypersensitivity (CVH) rats and its possible mechanism. Methods Newborn SD rats were given CVH rat model by colorectal distension (CRD) on the 8th, 10th and 12th day after birth. Thirty rats with successful CVH model were randomly divided into CVH model group (CVH group), CVH + injection of saline into PVN group (NS group), CVH+ injection of Glu into PVN (3, 6, and 12 μg Glu, namely G3, G6, and G12, respectively), 6 rats in each group, and 6 SD rats with matching body mass were taken as sham operation group (Sham group). The pain behavior of the rats was evaluated by pain threshold, abdominal withdrawal reflex (AWR) score, and abdominal external oblique muscle electromyography (EMG). The expression of arginine vasopressin (AVP) and the proliferation of colon tissue were detected by immunohistochemical staining. The apoptosis of colon tissue was detected by TUNEL. Results Compared with the NS group, the pain thresholds of the G3, G6 and G12 groups increased, and the AWR scores and EMG amplitudes decreased. The differences were statistically significant(Pain threshold: t=7.65, 16.31, 24.78, both P<0.05; AWR scores: t=-2.98, -4.77, -7.29, both P<0.05; EMG amplitudes: t=-3.06, -5.75, -8.92, both P<0.05). Compared with the Sham group, the expression of AVP in PVN of the CVH group and NS group decreased ((42.63±5.20) %, (18.67±2.94) %, (17.53±2.47) %; t=6.95, t=7.56, both P<0.05). The expression of AVP was increased after different doses of Glu into PVN, and the AVP level in G12 group ((18.15±6.49)%) was higher than that of NS group, the difference was statistically significant (t=-4.21, P<0.05). Compared with the Sham group, the expression of PCNA in colonic mucosal cells of the CVH group and NS group decreased ((65.48±1.68) %, (18.39±1.67) %, (17.69±1.68) %; t=34.35, t=34.80, both P<0.05). The expression of PCNA was increased after different doses of Glu injected into PVN, and the PCNA level in G12 group ((59.91±5.63)%) was higher than that of NS group, the difference was statistically significant (t=-12.44, P<0.05). Compared with the Sham group, the expression of apoptotic cells in colonic mucosal cells of the CVH group and NS group increased ((23.38±11.40)%, (83.79±3.57)%, (80.91±2.47)%; t=-8.77, t=-8.54, both P<0.05). The expression of apoptotic cells was decreased after different doses of Glu into PVN, and the G12 group was ((18.15±6.49) %). Compared with NS group, the difference was statistically significant (t=15.65, P<0.05). Conclusion Injection of Glu into hypothalamic PVN can alleviate the visceral pain behaviors in CVH rats, and its mechanism may be related to arginine vasopressin. Key words: Chronic visceral hypersensitivity; Hypothalamic paraventricular nucleus; Glutamate; Arginine vasopressin; Pain; Rat

Modulation of COX-2, INF-ɣ, glutamatergic and opioid systems contributes to antinociceptive, anti-inflammatory and anti-hyperalgesic effects of bis(3-amino-2-pyridine) diselenide

Preclinical assays play a key role in research in research on the neurobiology of pain and the development of novel analgesics. Drugs available for the treatment of inflammatory pain are not fully effective and show adverse effects. Thus, we investigated the antinociceptive, anti-inflammatory and anti-hyperalgesic effects of bis(3-amino-2-pyridine) diselenide (BAPD), a new analgesic drug prototype. BAPD effects were investigated using nociception models induced by chemical (glutamate), immunologic (Freund's Complete Adjuvant - CFA) and thermal stimuli in Swiss mice. Mice were orally (p.o.) treated with BAPD (0.1–50 mg/kg) 30 min prior to the glutamate and hot-plate tests and a time–course (0.5 up to 8 h) of the antinociceptive effect of BAPD (50 mg/kg, p. o.) was evaluated in a CFA model. In the CFA model, BAPD effects on cyclooxygenase-2 (COX-2), tumor necrosis factor (TNFα) and interferon-γ (INF-γ) expression, myeloperoxidase (MPO) activity, oxidative (2,2′-Azino-bis-3-ethylbenzothiazoline 6-sulfonic acid and 2,2-diphe- nyl-1-picrylhydrazyl levels) and histological parameters were evaluated. The safety of the compound (50 and 300 mg/kg, p. o.) was verified for 72 h. BAPD reduced the licking time induced by glutamate and caused an increase in latency response to thermal stimulus. Naloxone reversed the antinociceptive effect of BAPD. Paw edema formation induced by glutamate or CFA injection was reduced by BAPD. Mechanical hyperalgesia induced by CFA was attenuated by BAPD. BAPD did not protect against the increase in MPO activity and decrease of the 2,2′-Azino-bis-3-ethylbenzothiazoline 6-sulfonic acid and 2,2-diphe- nyl-1-picrylhydrazyl levels induced by CFA. BAPD protected against histological alterations and reduction on the levels of gene expression COX-2 and INF-γ in the paw of mice exposed to CFA. BAPD was safe at the doses and time evaluated. BAPD exerts acute antinociceptive, anti-inflammatory and anti-hyperalgesic actions, suggesting that it may represent an alternative in the future development of new therapeutic strategies.

Investigating the Role of the Hypothalamus in Outcomes to Repetitive Mild Traumatic Brain Injury: Neonatal Monosodium Glutamate Does Not Exacerbate Deficits

Repetitive mild traumatic brain injury (RmTBI) is a prevalent and costly head injury particularly among adolescents. These injuries may result in long-term consequences, especially during this critical period of development. Insomnia and sleeping difficulties are frequently reported following RmTBI and greatly impair recovery. We sought to develop an animal model of exacerbated deficits following RmTBI by disrupting the hypothalamic circadian system. To accomplish this, we conducted RmTBI on adolescent rats that had received neonatal injections of monosodium glutamate (MSG), a known hypothalamic neurotoxin. We then examined behavioral, circadian, and epigenetic changes. MSG treated rats showed lower anxiety-like behaviors and displayed poor short-term working memory. We also showed changes in the morphology of the circadian clock in the suprachiasmatic nucleus (SCN) vasoactive intestinal polypeptide (VIP) immunostaining. VIP optical density in the SCN increased with MSG but decreased with RmTBI. There were changes in the expression of the clock genes and upregulation of the orexin receptors in response to RmTBI. MSG treated rats had longer telomere lengths than controls. Finally, although both MSG and RmTBI alone produced attenuated circadian amplitudes of activity and body temperature, exacerbated deficits were not identified in animals that received MSG and RmTBI. In sum, both MSG and RmTBI can alter behavior, circadian rhythm amplitude, SCN morphology, and gene expression independently, but the effects do not appear to be additive. Specific damage in the hypothalamus and SCN should be considered when patients experience sleeping problems following RmTBI, as this may improve therapeutic strategies.

Investigation of Injection Depth for Subretinal Delivery of Exogenous Glutamate to Restore Vision via Biomimetic Chemical Neuromodulation.

Chemical neuromodulation of the retina using native neurotransmitters to biomimetically activate target retinal neurons through chemical synapses is a promising biomimetic alternative to electrical stimulation for restoring vision in blindness caused by photoreceptor degenerative diseases. Recent research has shown that subretinal chemical stimulation could be advantageous for treating photoreceptor degenerative diseases but many of the parameters for achieving efficacious chemical neuromodulation are yet to be explored. In this paper, we investigated how the depth at which neurotransmitter is injected subretinally affects the success rate, spike rate characteristics (i.e., amplitude, response latency, and time width), and spatial resolution of chemical stimulation in wild-type Long Evans and photoreceptor degenerated S334ter-3 transgenic rat retinas in vitro. We compared the responses to injections of glutamate at the subretinal surface and two subsurface depths near the outer and inner plexiform layers and found that while injections at all depths elicited robust retinal ganglion cell responses, they differed significantly in terms of the spike rate characteristics and spatial resolutions across injection depths. Shallow subsurface injections near the outer plexiform layer evoked the highest spike rate amplitudes and had the highest spatial resolution and success rates, while deep subsurface injections near the inner plexiform layer elicited the shortest latencies and narrowest time widths. Our results suggest that surface injections are suboptimal for subretinal chemical neuromodulation, while shallow subsurface and deep subsurface injections may optimize high spatial and high temporal resolution, respectively. These findings have great significance for the design and development of a potential neurotransmitter-based subretinal prosthesis.

Monosodium Glutamate (MSG)-Induced Animal Model of Type 2 Diabetes.

In 1976, an animal model of type 2 diabetes (T2DM) was described by Cameron et al. using injection of monosodium glutamate (MSG) in KK mice during the neonatal period. Some years later, similar models have been developed by various doses and durations and the main of these models exhibited obesity and features of diabetes mellitus, including glycosuria, hyperglycemia, hyperinsulinemia, decreased glucose tolerance, and insulin sensitivity. Studies indicated that MSG treatment of newborn animals generates necrosis of neuronal cells of the hypothalamic ventromedial nucleus and arcuate nucleus. Neonatal MSG-treatment was related to normoglycemic-normoinsulinemic state at young ages and development of obesity and hyperinsulinemia at adult ages. Following observation of a severe hypertrophy of pancreatic islets due to the proliferation of β-cells in MSG-treated mice, this model has been proposed as a useful animal model of human T2DM. A higher dose of MSG (≥4mg/g body weight) accompanied by a longer follow-up duration (>6months) are needed to establish a typical animal model of T2DM.

Characteristics of Glutamate-Evoked Pain in the Masseter Region: Differences Between Targeted Injections in Subcutaneous, Muscle, and Bone Tissues

To investigate whether glutamate-evoked pain in the masseter region differs between three different depths of injection, targeting subcutaneous, muscle, and bone tissues. A total of 16 healthy volunteers participated and, in a randomized order, received injections of glutamate (1.0 M, 0.2 mL) and isotonic saline (0.9%, 0.2 mL) in the masseter region that targeted subcutaneous, intramuscular, and bone surface tissues. Following injection, pain intensity was measured using electronic visual analog scale (eVAS) and numeric rating scale (NRS) scores of unpleasantness, tiredness, tension, soreness, and stiffness. Pressure pain sensitivity (PPS), pain drawing areas, and McGill Pain Questionnaire (MPQ) scores were also assessed. Repeated-measures analysis of variance, McNemar test, and Tukey post hoc tests were used for statistical analyses. P < .05 was considered statistically significant. Overall, subcutaneous injections induced significantly more unpleasantness and pain than intramuscular injections, and PPS scores evoked after glutamate injection at the surface of the bone were significantly higher than after intramuscular glutamate injection. Subcutaneous glutamate injections were more often described as "sharp" and "pinching." The subcutaneous injection was more painful and unpleasant than the intramuscular injection. The glutamate injection at the surface of the bone sensitized the deep pain tissues to pressure stimulation. Clinically, it may be difficult to differentiate between the source or site of pain originating from the masseter region, but the specific quality and word descriptors could assist in differential diagnosis.

Root bark of Discaria americana attenuates pain: A pharmacological evidence of interaction with opioidergic system and TRP/ASIC channels

Ethnopharmacological relevanceDiscaria americana (Rhamnaceae) root bark infusion have been used in traditional medicine as antipyretic, tonic, ameliorative of stomach and skin diseases and diabetes. This study was designed to investigate whether the methanolic extract of the root bark of Discaria americana (MEDa) exhibits antinociceptive effects in mice. Furthermore, it was investigated the involvement of the opioidergic system in MEDa mechanism of action as well the interactions with TRP/ASIC channels in its effect. Materials and methodsThe antinociceptive effect of intra-gastric gavage (i.g.) of MEDa (0.3–300 mg/kg) was evaluated in mice subjected to acute chemical (acetic-acid, formalin, glutamate, capsaicin, cinnamaldehyde, and acidified saline) or thermal (hot plate) tests of pain. The involvement of opioid system was evaluated in the formalin test. A nonspecific effect of MEDa was observed by measuring locomotor activity and exploratory behavior in open field test. ResultsMEDa significantly reduced the number of writhing induced by acetic acid and inhibited the nociception in the two phases of formalin. These effects were inhibited by pretreatment with naloxone. The nociception induced by hot plate and intraplantar injection of glutamate, capsaicin, cinnamaldehyde and acidified saline were significantly inhibited by MEDa. Only the dose of 300 mg/kg altered the locomotor activity. ConclusionsOur results demonstrated, for the first time, that the methanolic extract of the root bark of Discaria americana presents antinociceptive effect in chemical and thermal stimuli and its analgesic properties can be due activation of the opioidergic system. These results support the use of Discaria americana in traditional medicine and demonstrate that this plant presents a therapeutic potential for the development of phytomedicines with antinociceptive profile.

Excitatory and inhibitory influence of exogenous neurotransmitters on reproduction in female rats

Neurotransmitters are mediators inside the nervous system responsible for transmitting neural-neural or neural-organs signals. Several neural studies have tried to unveil the role of such mediators whose action extended outside the nervous system such as immune, digestive, circulatory and reproductive systems. The present study aimed to investigate the role of the excitatory-glutamate and inhibitory-GABA transmitters in female rats reproduction including their effects on gonadotropins; luteinizing hormone (LH) and follicle stimulating hormone (FSH) and the sex steroids; estrogen (E2) and progesterone (P4) during the estrous cycle as well. Furthermore, the responsive changes on the ovarian tissue were also studied. Synthetic glutamate and GABA were injected intraperitoneally (ip) in those animals throughout four successive estrous cycles. Interestingly, the ip injections of glutamate increased the levels of LH, E2 and P4 but decreased those of FSH significantly. However, the ip injections of GABA significantly decreased the levels of LH in the 4th cycles and FSH throughout treatment period while it increased the levels of E2 and P4. All changes occurred in those reproductive hormones caused by glutamate has been recovered after cessation of glutamate and GABA injection except FSH, including; the 5th, 6th and 7th cycles. Regarding to histopathological examination, ovaries of treated rats showed deleterious changes. The glutamate-treated rats ovaries showed atrophy of the primary follicles with degenerative changes in those secondary and tertiary follicles with obvious degeneration in the granulosa cell layer with vacuolated cytoplasm. On the other hand, those received GABA showed degeneration of the oocytes with congestion of blood vessels supplying the corpora lutea (CL) associated with endothelial changes. The histopathological changes in CL have been improved after glutamate cessation while not changed after GABA cessation.

Comparison of masseter muscle referred sensations after mechanical and glutamate stimulation: a randomized, double-blind, controlled, cross-over study.

Referred sensations (RS) are commonly found in various musculoskeletal pain conditions. Experimental studies have shown that RS can be elicited through glutamate injection and mechanical stimulation. Despite this, differences and similarities between these modalities in RS outcomes remain unclear. The aim of this study was to assess differences between mechanical-induced and glutamate injection-induced RS in the trigeminal region. The present randomized, double-blind, controlled, cross-over study recruited 60 healthy participants who were assessed in 2 different sessions. In both sessions, pressure was applied to the masseter muscle with 4 different forces (0.5, 1, 2, and 4 kg), and glutamate (1 mol/L or 0.25 mol/L) was injected into the same area. Participants rated their perceived masseter sensations and rated and drew any RS they experienced. No difference was found in number of participants reporting RS after glutamate injection compared with mechanical stimulation. More participants reported RS when the stimulus was painful compared with a nonpainful stimulus. Furthermore, it was shown that the more intense the stimulus, the higher the frequency of RS. Finally, RS centre-of-gravity location was similar between the 2 sessions. In summary, RS was elicited in healthy individuals through both modalities, and no differences in frequency of RS were observed in the orofacial region. Hence, RS does not seem to be modality-dependent, and only the painfulness of the stimulus caused an increase in frequency of RS. Finally, RS location for each participant was similar in both sessions possibly indicating a preferred location of referral. These findings may have implications for our understanding of RS in craniofacial pain conditions.

Genistein Antagonizes 17β-Estradiol Effects on Glutamate-Evoked Masseter Muscle Hypernociception in Rats.

Temporomandibular disorders (TMDs) predominantly affect women of reproductive ages, with pain as the main symptom. The aim of the present study was to examine the effects of 17β-estradiol (E2) on glutamate-evoked hypernociception of masseter muscle and to examine whether genistein could antagonize the effects of E2 in female rats. Injection of glutamate into the masseter muscle dose-dependently decreased head withdrawal thresholds, a parameter for mechanical hypernociception. Head withdrawal thresholds in ovariectomized rats also decreased with increasing doses of E2 replacement, and were further aggravated by injection of glutamate (1M, 40μL) into the masseters. Genistein at doses of 7.5 and 15 mg/kg antagonized E2-induced hypernociception of masseter muscle, and at doses of 7.5, 15, and 30 mg/kg also antagonized E2 potentiation of glutamate-evoked hypernociception of masseter muscle. Genistein produced optimal antagonistic effects of E2 on nociception behavior at a dose of 15 mg/kg. On the molecular level, tyrosine phosphorylation of the NR2B subunit of the N-methyl-D-aspartate receptor (pNR2B) and phosphorylated mitogen-activated protein kinase (pERK1/2) were significantly upregulated in the hippocampus following glutamate injection and were further potentiated by E2 replacement. Genistein at dose of 15 mg/kg partially reversed E2-potentiated glutamate-evoked upregulation of pNR2B and pERK1/2 expression in the hippocampus. These results indicated that moderate doses of genistein could antagonize E2 enhanced glutamate-evoked hypernociception of masseter muscle possibly via N-methyl-D-aspartate receptor and ERK1/2 signaling pathways in the hippocampus.

Analgesic Effects Elicited by Neuroactive Mediators Injected into the ST 36 Acupuncture Point on Inflammatory and Neuropathic Pain in Mice

The present study evaluates whether the injection of serotonin, acetylcholine, glutamate, bradykinin, histamine, or substance P (SP) into the Zusanli (Stomach 36, ST 36) acupoint can also produce the acupuncture-induced antinociceptive effect on inflammatory or neuropathic pain. In this in vivo experimental study, a total of 450 male Swiss mice were used. Mice were injected with saline or complete Freund's adjuvant (CFA) or subjected to sham or chronic constriction injury (CCI) surgery. After the establishment of the inflammatory (4 hours) or the neuropathic pain (3 days), the animals (n = 6) received manual acupuncture, sham acupuncture, or injection of saline, serotonin, acetylcholine, glutamate, bradykinin, histamine, or SP into the ST 36 and were evaluated for up to 24 hours. Mechanical threshold was evaluated, and the L4-L6 dorsal root ganglion was used for analysis of the transient receptor potential vanilloid type 1 overexpression. The mice from both the CFA and CCI models treated with manual acupuncture had significant increases in the thresholds for more than 24 hours. Sham acupuncture stimulation did not change the thresholds. In the mice injected with each of the mediators, the thresholds were significantly increased for all times in both the CFA and CCI models. Transient receptor potential vanilloid type 1 overexpression in CFA and CCI mice was reduced at all times by injection of serotonin, acetylcholine, or SP but not by injection of glutamate, histamine, or bradykinin. Our data suggest that the neuroactive mediators released by acupuncture-induced tissue injury may contribute to acupuncture-induced analgesia.

Protective effect and mechanism of injection of glutamate into cerebellum fastigial nucleus on chronic visceral hypersensitivity in rats

AimsWe investigated the effects of chemical stimulation of cerebellum fastigial nucleus (FN) on the chronic visceral hypersensitivity (CVH) and its possible mechanism in rats. Main methodsWe stimulated the FN by microinjecting glutamate into the FN, in order to explore whether the cerebellum fastigial nucleus played a role on CVH in rat. The model of CVH was established by colorectal distension (CRD) in neonatal rats. Abdominal withdrawal reflex (AWR) scores, pain threshold, and amplitude of electromyography (EMG) were used to assess the hyperalgesia. Key findingsWe showed that microinjection of l-glutamate (Glu) into the FN markedly attenuated hyperalgesia. The protective effect of FN was prevented by pretreatment with the glutamate decarboxylase inhibitor, 3-mercaptopropionic acid (3-MPA) into the FN or GABAA receptor antagonist, bicuculline (Bic) into the LHA (lateral hypothalamic area). The expressions of protein Bax, caspase-3 were decreased, but the expression of protein Bcl-2 was increased after chemical stimulation of FN. These results indicated that the FN participated in regulation of CVH, and was a specific area in the CNS for exerting protective effects on the CVH. In addition, LHA and GABA receptor may be involved in this process. SignificanceOur findings might provide a new and improved understanding of the FN function, and might show an effective treatment strategy for the chronic visceral hypersensitivity.

Early Nodal and Paranodal Disruption in Autoimmune Optic Neuritis.

Disturbances in the nodes of Ranvier are an early phenomenon in many CNS disorders, including the autoimmune demyelinating disease multiple sclerosis (MS). Using an animal model of optic neuritis, a common early symptom of MS, we have investigated nodal and paranodal compartments in the optic nerve during disease progression. Both nodes and paranodes, as identified by immunohistochemistry against sodium channels (Nav) and Caspr, respectively, were observed to increase in length during the late induction phase of the disease, prior to onset of the demyelination and immune cell infiltration characteristic of optic neuritis. These changes were correlated with both axonal stress and microglial/macrophage activation, and were most apparent in the vicinity of the retrobulbar optic nerve head, the unmyelinated region of the optic nerve where retinal ganglion cell axons exit the retina. Using intravitreal glutamate injection as a model of a primary retinal insult, we demonstrate that this can induce similar nodal and paranodal changes. This may suggest that onset of neurodegeneration in the absence of demyelination, as reported in several studies into the nonaffected eyes of MS patients, may give rise to subtle disturbances in the axo-glial junction.

Microfluidics-Based Subretinal Chemical Neuromodulation of Photoreceptor Degenerated Retinas.

Retinal prostheses can restore rudimentary vision in cases of photoreceptor degeneration through electrical stimulation, but face difficulties achieving high spatial resolution because electrical current is an inherently unnatural stimulus. We investigated the therapeutic feasibility of using patterned delivery of the glutamate neurotransmitter, a primary agent of natural synaptic communication of the retina, as a biomimetic chemical alternative to electrical current for neuromodulation of photoreceptor degenerate retina. We injected small quantities of the neurotransmitter glutamate into the subretina of 20 explanted photoreceptor degenerated S334ter-3 rat retinas using glass micropipettes and a prototype multiport microfluidic device to accomplish single- and multisite stimulation in vitro. The effects of chemical stimulation were characterized by recording neural responses from retinal ganglion cells (RGCs) using a multielectrode array. Subretinally injected exogenous glutamate activates RGCs, despite the substantial anatomic and physiologic changes caused by retinal remodeling, eliciting robust neural responses. The presence of excitatory and inhibitory RGC responses provides evidence that exogenous glutamate differentially activated neurons presynaptic to RGCs, likely inner retinal neurons belonging to the OFF and ON pathways. We also demonstrate that glutamate injections can evoke focal RGC responses with spatial resolutions comparable to or better than current generation electrical prostheses and, when applied at multiple sites simultaneously with the multiport microfluidic device, can produce spatially patterned neural responses. These significant results establish that chemical stimulation of degenerated retinas with neurotransmitters is an effective neuromodulation strategy with the potential of restoring high-resolution visual perception in patients rendered blind through photoreceptor degeneration.

Interaction Between Central Oxytocinergic and Glutamatergic Systems on Food Intake in Neonatal Chicks: Role of NMDA and AMPA Receptors

The present study was designed to examine the interconnection between oxytocinergic and glutamatergic systems on feeding behavior in neonatal chicks. In experiment 1, FD3 chicken ICV injected with (A) saline (control solution), (B) oxytocin (10 µg), (C) MK-801(NMDA receptor antagonist, 15 nmol) and (D) oxytocin + MK-801. In experiment 2, (A) control solution, (B) oxytocin (10 µg), (C) CNQX (390 nmol) and (D) oxytocin + CNQX were injected. Experiments 3–6 were similar to experiment 1, except FD3 chicks ICV injected with CNQX (AMPA glutamate receptors antagonist, 390 nmol), AIDA (mGLUR1 glutamate receptors antagonist, 2 nmol), LY341495 (mGLUR2 glutamate receptors antagonist, 150 nmol) and UBP1112 (mGLUR3 glutamate receptors antagonist, 2 nmol) instead of MK-801, respectively. In experiment 7, injections were (A) control solution, (B) glutamate (300 nmol), (C) ABN-297 (9 nmol) and (D) glutamate + ABN-297. Then the cumulative food intake measured until 120 min post injection. According to the results, ICV injection of glutamate decreased food intake and co-injection of the glutamate + ABN-297 increased food consumption in neonatal broiler (P < 0.001). ICV injection of oxytocin, significantly decreased food intake in neonatal chicks (P < 0.001). Also, MK-801 significantly attenuated oxytocin- induced hypophagia in chicks (P < 0.001). In addition, combination of oxytocin plus CNQX significantly decreased hypophagic effect of the oxytocin in neonatal chicks (P < 0.001). These results suggested interconnection between central oxytocinergic and glutamatergic systems on feeding behavior is probably mediated via NMDA and AMPA receptors.

Influence of glutamate-evoked pain and sustained elevated muscle activity on blood oxygenation in the human masseter muscle.

This study aimed to investigate the effect of glutamate-evoked masseter muscle pain on intramuscular oxygenation during rest and sustained elevated muscle activity (SEMA). Seventeen healthy individuals participated in two sessions in which they were injected with glutamate and saline in random order. Each session was divided into three, 10-min periods. During the first (period 1) and the last (period 3) 10-min periods, participants performed five intercalated 1-min bouts of masseter SEMA with 1-min periods of 'rest'. At onset of the second 10-min period, glutamate (0.5ml, 1M; Ajinomoto, Tokyo, Japan) or isotonic saline (0.5ml; 0.9%) was injected into the masseter muscle and the participants kept the muscle relaxed in a resting position for 10min (period 2). The hemodynamic characteristics of the masseter muscle were recorded simultaneously during the experiment by a laser blood-oxygenation monitor. The results demonstrated that glutamate injections caused significant levels of self-reported pain in the masseter muscle; however, this nociceptive input did not have robust effects on intramuscular oxygenation during rest or SEMA tasks. Interestingly, these findings suggest an uncoupling between acute nociceptive activity and hemodynamic parameters in both resting and low-level active jaw muscles. Further studies are needed to explore the pathophysiological significance of blood-flow changes for persistent jaw-muscle pain conditions.

Antinociceptive activity of Cistanche salsa stolons, growing in the Republic of Kazakhstan

Herba Cistanche (Cistanche species) in Traditional Chinese Medicine is used for the treatment of several diseases and symptoms, to include pain. The objective of this study was to evaluate the antinociceptive effect of the hydroethanol extract of Cistanche salsa (C.A.Mey.) Beck, Orobanchaceae, stolons in animal models of pain. Chemical composition of Herba Cistanche was analyzed by HPLC-UV. Mice Swiss Webster (25–30g, n=6) were orally pre-treated with Herba Cistanche (10, 30 or 100mg/kg) and evaluated in the formalin test and in the capsaicin- or glutamate-induced licking response. Kazakh Herba Cistanche is composed mainly by phenylpropanoid glycosides, from which echinacoside, acteoside and tubuloside B are the main constituents. When Herba Cistanche was administered to mice it had an effect in both phases of the formalin test (77% activity at 30mg/kg for phase 1 and 62% activity at 100mg/kg for phase 2) suggesting analgesic and anti-inflammatory properties. Kazakh Herba Cistanche was able to reduce the animals licking time after injection of glutamate (81% reduction at 30mg/kg) and capsaicin (81% reduction at 100mg/kg). We conclude that phenolics present in the hydroethanol extract of C. salsa could be responsible for its pharmacological profile. In order to source a good quality raw material for Traditional Chinese Medicine we recommended this Kazakh species to be standardized using echinacoside and acteoside as markers.