Expression of glycine receptor α3 subunit in neuropathic and inflammatory central pain sensitization

INTRODUCTION: Increasing evidence suggests that changes in the balance of excitatory/inhibitory neurotransmission are involved in the development of the majority of chronic pain forms. In this context, impairment in glycine mediated inhibitory neurotransmission is thought to play a critical role in the disinhibition that accounts for the development and maintenance of central pain hypersensitivity. AIMS: The goal of this study was to evaluate the Glycine Receptor α3 subunit (α3GlyR) expression in neuropathic (Chronic Constriction Injury, CCI) and inflammatory (Zymosan A injected) animal models of chronic pain. RESULTS AND CONCLUSION: RT-qPCR analysis of spinal cord samples showed that glra3 gene expression does not change after 3 days of CCI and 4 hours of Zymosan A injection. However, we found that protein levels evaluated by Western blot increased after inflammatory pain. These data suggest that central sensitization is differentially regulated depending on the type of pain. α3GlyR protein expression plays an important role in the first step of inflammatory pain establishment.

Kir2.1 Channel Regulation of Glycinergic Transmission Selectively Contributes to Dynamic Mechanical Allodynia in a Mouse Model of Spared Nerve Injury / 神经科学通报·英文版

Neuropathic pain is a chronic debilitating symptom characterized by spontaneous pain and mechanical allodynia. It occurs in distinct forms, including brush-evoked dynamic and filament-evoked punctate mechanical allodynia. Potassium channel 2.1 (Kir2.1), which exhibits strong inward rectification, is and regulates the activity of lamina I projection neurons. However, the relationship between Kir2.1 channels and mechanical allodynia is still unclear. In this study, we first found that pretreatment with ML133, a selective Kir2.1 inhibitor, by intrathecal administration, preferentially inhibited dynamic, but not punctate, allodynia in mice with spared nerve injury (SNI). Intrathecal injection of low doses of strychnine, a glycine receptor inhibitor, selectively induced dynamic, but not punctate allodynia, not only in naïve but also in ML133-pretreated mice. In contrast, bicuculline, a GABA receptor antagonist, induced only punctate, but not dynamic, allodynia. These results indicated the involvement of glycinergic transmission in the development of dynamic allodynia. We further found that SNI significantly suppressed the frequency, but not the amplitude, of the glycinergic spontaneous inhibitory postsynaptic currents (gly-sIPSCs) in neurons on the lamina II-III border of the spinal dorsal horn, and pretreatment with ML133 prevented the SNI-induced gly-sIPSC reduction. Furthermore, 5 days after SNI, ML133, either by intrathecal administration or acute bath perfusion, and strychnine sensitively reversed the SNI-induced dynamic, but not punctate, allodynia and the gly-sIPSC reduction in lamina IIi neurons, respectively. In conclusion, our results suggest that blockade of Kir2.1 channels in the spinal dorsal horn selectively inhibits dynamic, but not punctate, mechanical allodynia by enhancing glycinergic inhibitory transmission.

Anxiolytic Action of Taurine via Intranasal Administration in Mice

Taurine has a number of beneficial pharmacological actions in the brain such as anxiolytic and neuroprotective actions. We explored to test whether taurine could be transported to the central nervous system through the intranasal route. Following intranasal administration of taurine in mice, elevated plus maze test, activity cage test and rota rod test were carried out to verify taurine’s effect on anxiety. For the characterization of potential mechanism of taurine’s anti-anxiety action, mouse convulsion tests with strychnine, picrotoxin, yohimbine, and isoniazid were employed. A significant increase in the time spent in the open arms was observed when taurine was administered through the nasal route in the elevated plus maze test. In addition, vertical and horizontal activities of mice treated with taurine via intranasal route were considerably diminished. These results support the hypothesis that taurine can be transported to the brain through intranasal route, thereby inducing anti-anxiety activity. Taurine’s anti-anxiety action may be mediated by the strychnine-sensitive glycine receptor as evidenced by the inhibition of strychnine-induced convulsion.

Potentiation of the glycine response by serotonin on the substantia gelatinosa neurons of the trigeminal subnucleus caudalis in mice

The lamina II, also called the substantia gelatinosa (SG), of the trigeminal subnucleus caudalis (Vc), is thought to play an essential role in the control of orofacial nociception. Glycine and serotonin (5-hydroxytryptamine, 5-HT) are the important neurotransmitters that have the individual parts on the modulation of nociceptive transmission. However, the electrophysiological effects of 5-HT on the glycine receptors on SG neurons of the Vc have not been well studied yet. For this reason, we applied the whole-cell patch clamp technique to explore the interaction of intracellular signal transduction between 5-HT and the glycine receptors on SG neurons of the Vc in mice. In nine of 13 neurons tested (69.2%), pretreatment with 5-HT potentiated glycine-induced current (I(Gly)). Firstly, we examined with a 5-HT₁ receptor agonist (8-OH-DPAT, 5-HT(1/7) agonist, co-applied with SB-269970, 5-HT₇ antagonist) and antagonist (WAY-100635), but 5-HT₁ receptor agonist did not increase IGly and in the presence of 5-HT₁ antagonist, the potentiation of 5-HT on I(Gly) still happened. However, an agonist (α-methyl-5-HT) and antagonist (ketanserin) of the 5-HT₂ receptor mimicked and inhibited the enhancing effect of 5-HT on I(Gly) in the SG neurons, respectively. We also verified the role of the 5-HT₇ receptor by using a 5-HT₇ antagonist (SB-269970) but it also did not block the enhancement of 5-HT on I(Gly). Our study demonstrated that 5-HT facilitated I(Gly) in the SG neurons of the Vc through the 5-HT₂ receptor. The interaction between 5-HT and glycine appears to have a significant role in modulating the transmission of the nociceptive pathway.

Familiar Hyperekplexia, a Potential Cause of Cautious Gait: A New Korean Case and a Systematic Review of Phenotypes

Familial hyperekplexia, also called startle disease, is a rare neurological disorder characterized by excessive startle responses to noise or touch. It can be associated with serious injury from frequent falls, apnea spells, and aspiration pneumonia. Familial hyperekplexia has a heterogeneous genetic background with several identified causative genes; it demonstrates both dominant and recessive inheritance in the α1 subunit of the glycine receptor (GLRA1), the β subunit of the glycine receptor and the presynaptic sodium and chloride-dependent glycine transporter 2 genes. Clonazepam is an effective medical treatment for hyperekplexia. Here, we report genetically confirmed familial hyperekplexia patients presenting early adult cautious gait. Additionally, we review clinical features, mode of inheritance, ethnicity and the types and locations of mutations of previously reported hyperekplexia cases with a GLRA1 gene mutation.

Hearing Profile of Brazilian Forestry Workers' Noise Exposure

Introduction Researchers studying the hearing health of forestry workers have revealed the presence of a noise-induced hearing loss (NIHL) in this population and have concluded that the vibration of the equipment, the carbon monoxide released by motors, and pesticides might also contribute to NIHL. Objective To analyze the noise exposure in the Brazilian forestry industry workers and the effects on hearing. Methods The study sample comprised 109 employees of a company that specialized in reforestation. Their participants' mean age was 35.5 years (21 to 54 years), mean tenure at the company was 3.9 years (1 to 13 years), and mean total duration of noise exposure was 12.3 years (1 to 30 years). The existing documentation reporting on the jobs risk analysis was examined, noise level was measured, and pure tone audiometry was performed in all participants. Participants were divided into three groups according to their noise exposure levels in their current job. Results Of the participants who were exposed to noise levels less than 85 dBA (decibels with A-weighting filter), 23.8% had hearing loss, and 5.5% of the participants who were exposed to noise ranging from 85 to 89.9 dBA and 11% of the participants who were exposed to noise greater than 90 dBA had audiogram results suggestive of NIHL. Conclusion The implementation of a hearing loss prevention program tailored to forestry workers is needed. .

Pharmacological characteristics of glycine receptors in rat hippocampal pyramidal cells / 中南大学学报(医学版)

OBJECTIVE@#To investigate function of glycine receptors (GlyRs) at the hippocampal CA1 pyramidal cells and to characterize the pharmacological properties of these receptors at early postnatal stage.@*METHODS@#We used whole cell patch clamp recording to study the current response in the acutely prepared hippocampal slices from postnatal day 11-13 rats induced by glycine applied in the artificial cerebrospinal fluid.@*RESULTS@#Application of glycine to the pyramidal cells elicited strychnine sensitive chloride currents. EC50 for GlyRs respond to glycine was 123. 23 μmol/L and Hill coefficient was 1.24. Picrotoxin could partly blocked the currents.@*CONCLUSION@#Strychnine sensitive glycine receptors are functionally expressed in CA1 pyramidal neurons in rat hippocampal CA1 area at early postnatal stage, and some of GlyRs are αβ heteromeric receptors.

Glycine- and GABA-mimetic Actions of Shilajit on the Substantia Gelatinosa Neurons of the Trigeminal Subnucleus Caudalis in Mice

Shilajit, a medicine herb commonly used in Ayurveda, has been reported to contain at least 85 minerals in ionic form that act on a variety of chemical, biological, and physical stressors. The substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis (Vc) are involved in orofacial nociceptive processing. Shilajit has been reported to be an injury and muscular pain reliever but there have been few functional studies of the effect of Shilajit on the SG neurons of the Vc. Therefore, whole cell and gramicidin-perfotrated patch clamp studies were performed to examine the action mechanism of Shilajit on the SG neurons of Vc from mouse brainstem slices. In the whole cell patch clamp mode, Shilajit induced short-lived and repeatable inward currents under the condition of a high chloride pipette solution on all the SG neurons tested. The Shilajit-induced inward currents were concentration dependent and maintained in the presence of tetrodotoxin (TTX), a voltage gated Na+ channel blocker, CNQX, a non-NMDA glutamate receptor antagonist, and AP5, an NMDA receptor antagonist. The Shilajit-induced responses were partially suppressed by picrotoxin, a GABAA receptor antagonist, and totally blocked in the presence of strychnine, a glycine receptor antagonist, however not affected by mecamylamine hydrochloride (MCH), a nicotinic acetylcholine receptor antagonist. Under the potassium gluconate pipette solution at holding potential 0 mV, Shilajit induced repeatable outward current. These results show that Shilajit has inhibitory effects on the SG neurons of Vc through chloride ion channels by activation of the glycine receptor and GABAA receptor, indicating that Shilajit contains sedating ingredients for the central nervous system. These results also suggest that Shilajit may be a potential target for modulating orofacial pain processing.

Effect of Strychinine, a Glycine Inhibitor, on the Programmed Cell Death of Motoneurons during the Chick Development

In this study, we report that the treatment of strychinine (STR), an inhibitor of glycine receptor, induced premature onset of programmed cell death (PCD) of developing chick motoneurons (MNs). Treatment of STR on E4 chick embryo increased the apoptosis of MN on E5 when MN PCD does not occur normally. On the other hand, treatment of STR from E3 or E5 for 24 hours did not significantly influence the extent of MN PCD, indicating that the STR effect is developmental stage-specific. However, the expression of glycine receptor isoform was low on E3-4, and other glycine receptor antagonists did not exhibit PCD-promoting activity, suggesting that the STR action on PCD is not related to the glycine receptor activation. Identification of the target molecule for STR action may provide novel mechanism how the onset of developmental PCD is regulated.

Decreased level of soluble receptors of advanced glycated end products [sRAGE] and Glycine 82 Serine [G82S] polymorphism in patients with RA

The receptor for advanced glycated end products [RAGE] is a multi-ligand receptor expressed as a cell surface molecule, interacting with diverse ligands. Since soluble RAGE [sRAGE] acts as a competitive receptor for cellular RAGE, the balance between these two types of receptors might be of importance in the pathogenesis of RA. To evaluate the levels of sRAGE in patients with RA compared with healthy controls and to assess the relationship between sRAGE levels and disease characteristics. Also, we assessed the association between the gene variants and the sRAGE level and disease activity. The study included 33 patients with RA and 16 healthy normal controls. All patients and controls are subjected to full clinical assessment, joint examination including tender joint count [TJC], swollen joint count [STC] and estimation of DAS 28 and laboratory investigations including CBC, ESR, urine analysis, kidney function tests, liver function tests, RF and C-reactive protein [CRP]. Soluble RAGE was determined by enzymatic immunoassay and molecular study was done for single nucleotide polymorphisms [SNP] in the glycine 82 serine [G82S] of the RAGE gene. RF was positive in 72.7% of patients and was negative in all controls. CRP was significantly higher in RA patients as compared with controls [p < 0.01]. Serum levels of sRAGE were significantly lower in RA patients than controls. RA: Rheumatoid arthritis. AGEs: Advanced glycation endproducts. sRAGE: Soluble receptor for advanced glycation end products. NF-KB: Nuclear factor-kappaB. DAS28: Disease activity score. MS: Morning stiffness. TJC: Tender joint count. SJC: Swollen joint count. CRP: C-reactive protein. SNP: Single nucleotide polymorphisms. G82S: Glycine 82 serine gene polymorphism. HMGB1: High mobility group box I or amphoterin. MMPs: Matrix metalloproteinases. [840.11 +/- 230.32 versus 1111.59 +/- 143.20, p < 0.05]. Genotyping of the RAGE gene showed G82S in 22 out of 33 RA patients, 5 of them were homozygous for the RAGE serine 82 allele, while genotyping in the control subjects showed polymorphisms in the G82S in 5 out of 16, only one of them was homozygous for the RAGE G82S allele, indicating significantly increased G82S allele in RA patients as compared with controls [p < 0.05]. The G82S allele was related to the MS, CRP and sRAGE in RA patients. The sRAGE levels were significantly lower in RA patients with more disease activity as indicated by MS, TJC and CRP. The sRAGE levels were significantly lower in RA patients with cardiac disease than those without cardiac disease. Linear regression analysis detected CRP and gene polymorphism as significant predictors for sRAGE. The levels of sRAGE were significantly lower in patients with RA and this reduction was correlated with the disease activity and glycine 82 serine gene polymorphism. Thus, the sRAGE may be an important marker of disease activity and can be used as a therapeutic target in these conditions

Immunohistochemical Localization of Glycine Receptor (alpha1+alpha2) in the Auditory Brain Stem of Circling Mouse / 대한해부학회지

Hearing loss in adults can stem from damage to the cochlea and the cochlear nerves inflicted by intense noise, mechanical trauma, or disease. Hearing loss is associated with degenerative changes in central auditory pathways, and hearing deficits are often accompanied by changes in the synaptic organization of the central auditory pathways. In addition to structural rearrangements, hearing loss may induce changes in the strength of synaptic transmissions. These effects may alter both transient and persistent regulation of transmitter release from glutamatergic, glycinergic, and GABAergic pathways in the auditory brain stem. The converging excitatory and inhibitory inputs are exquisitely organized topographically and are aligned perfectly with each other. The LSO and MNTB in the mammalian auditory brain stem provide and receive many glycinergic inputs. Thus, this auditory system is a useful model to study inhibitory synaptic development. However, little is known about the inhibitory synapses in the central nervous system. First, we used immunohistochemistry to compare the glycine receptor (GlyR) distribution in the LSO and MNTB, which project glycinergic inhibitory input into the auditory brainstem, in circling mice (P16), which have a spontaneous mutation in the inner ear, with wild-type mice. The relative immunoreactive density of the LSO was 86.4+/-7.2 in wild-type, 76.7+/-10.7 in heterozygous, and 61.1+/-4.1 in homozygous mice. The relative immunoreactive density of the MNTB was 97.6+/-8.7 in wild-type, 91.7+/-8.9 in heterozygous, and 74.9+/-7.8 in homozygous mice. These results reveal a decreased GlyR immunoreactivity in both the LSO and MNTB, which may be attributable to a postsynaptic decrease in GlyR number. Our model uses congenitally deaf mice, in which both spontaneous and evoked auditory nerve activity are disrupted because of dysfunctional hair cell-spiral ganglion cell transmission. This provides a naturally occurring model that may provide valuable insights into the central aspects of human congenital deafness in addition to the central consequences of a lack of auditory nerve activity. Our results are likely to be relevant to our understanding of the central changes underlying human hereditary deafness.

The glycine receptor / 한양의대학술지

The glycine receptor (GlyR), a member of the pentameric ligand gated ion channel family, is best known for mediating inhibitory neurotransmission in motor and sensory circuits of the spinal cord, and is also present in the brain stem, cerebellum and retina When glycine binds to its site on the external receptor surface, the pore opens allowing Cl- to passively diffuse across the membrane. Because molecules that increase GlyR current may have clinical potentials as muscle relaxant and peripheral analgesic drug, it is important to understand and study the physiology and molecular pharmacology of the GlyR. We review the pharmacology and physiologic properties, structures, function and heritable disorders of glycinergic neurotransmission.

Glycine receptors contribute to cytoprotection of glycine in myocardial cells / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The classic glycine receptor (GlyR) in the central nervous system is a ligand-gated membrane-spanning ion channel. Recent studies have provided evidence for the existence of GlyR in endothelial cells, renal proximal tubular cells and most leukocytes. In contrast, no evidence for GlyR in myocardial cells has been found so far. Our recent researches have showed that glycine could protect myocardial cells from the damage induced by lipopolysaccharide (LPS). Further studies suggest that myocardial cells could contain GlyR or binding site of glycine.</p><p><b>METHODS</b>In isolated rat heart damaged by LPS, the myocardial monophasic action potential (MAP), the heart rate (HR), the myocardial tension and the activities of lactate dehydrogenase (LDH) from the coronary effluent were determined. The concentration of intracellular free calcium ([Ca(2+)](i)) was measured in cardiomyocytes injured by LPS and by hypoxia/reoxygenation (H/R), which excludes the possibility that reduced calcium influx because of LPS neutralized by glycine. Immunohistochemistry was used to detect the GlyR in myocardial tissue. GlyR and its subunit in the purified cultured cardiomyocytes were identified by Western blotting.</p><p><b>RESULTS</b>Although significant improvement in the MAP/MAPD(20), HR, and reduction in LDH release were observed in glycine + LPS hearts, myocardial tension did not recover. Further studies demonstrated that glycine could prevent rat mycordial cells from LPS and hypoxia/reoxygenation injury (no endotoxin) by attenuating calcium influx. Immunohistochemistry exhibited a positive green-fluorescence signaling along the cardiac muscle fibers. Western blotting shows that the purified cultured cardiomyocytes express GlyR beta subunit, but GlyR alpha1 subunit could not be detected.</p><p><b>CONCLUSIONS</b>The results suggest that glycine receptor is expressed in cardiomyocytes and participates in cytoprotection from LPS and hypoxia/reoxygenation injury. Glycine could directly activate GlyR on the cardiomyocytes and prevent calcium influx into the cardiomyocytes.</p>

Effects of Nitric Oxide on Inhibitory Receptors of Rod Bipolar Cells of Rat Retina

The effects of nitric oxide (NO) on inhibitory neurotransmitter receptors and some types of inhibitory receptors in dissociated rod bipolar cell (RBC) were investigated. In the whole cell voltage-clamping mode, the gamma-aminobutyric acid (GABA) activated current showed both sustained and transient components. GABA activated transient current was fully blocked by bicuculine, a GABAA receptor antagonist. The cis-4-aminocrotonic acid (CACA), a GABAC receptor agonist, evoked the sustained current that was not blocked by bicuculline (BIC). Glycine activated the transient current. These results indicate that the RBCs possess GABAA, GABAC, and glycine inhibitory receptors. Sodium nitroprusside (SNP), a NO analogue, reduced the currents activated by GABAA receptor only, however, did not reduce the currents activated by either GABAC or glycine receptors. This study signifies further that only NO depresses the fast inhibitory response activated by GABAA receptor in RBC. We, therefore, postulate that NO might depress the light-on/off transient inhibitory responses in RBCs in the rat retina.

Manganese poisoning reduces strychnine-insensitive glycine binding sites in the globus pallidus of the mouse brain / Reducción de los receptores glicinérgicos insensibles a estricnina en el globo pálido del cerebro de ratones intoxicados con manganeso

Manganese (Mn) poisoning is characterized by central nerous system manifestations, including psychiatric disturbances and estrapyramidal disorders. This metal is thought to produce neuronal degeneration due to cytotoxic products originated by oxidative stress and through an indirect excitotoxic process. In previous studies, we have found a reduction in the density of N-methyl-D-aspartate (NMDA) recognition sites in some brain areas of Mn-treated mice. Due to the close relationship between NMDA receptor complex, the [3H]-glycine ([3H]/Gly) binding was manganese choride for 8 weeks. Among all analyzed areas, only the globus pallidus showed a significant reduction in [3H]-Gly binding (27-28). The Gly binding decrease, focalized in the globus pallidus, could reflect a degeneration of structures containing strychnine-insensitive Gly receptors, since this area is the most frequently reported damaged brain region in Mn intoxication. Howerer, it might also be due to a Gly receptor down-regulation to control NMDA complex activation during Mn poisoning.

Canales para iones en las membranas celulares: algunos aspectos de interés clínico / Ionic channels in cellular membranes: somo aspects of clinical relevance

En el presente artículo se revisan brevemente las principales características de los canales para iones en las membranas celulares, su participación en diversos eventos fisiológicos y fisiopatológicos y se muestran ciertos aspectos de importancia clínica derivados de su estudio