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.
Animals ; Glycine ; Mice ; Neurons ; Neurotransmitter Agents ; Nociception ; Patch-Clamp Techniques ; Receptors, Glycine ; Serotonin ; Signal Transduction ; Substantia Gelatinosa

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.
Administration, Intranasal ; Animals ; Anxiety ; Arm ; Brain ; Central Nervous System ; Isoniazid ; Mice ; Picrotoxin ; Receptors, Glycine ; Seizures ; Strychnine ; Taurine ; Yohimbine

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.
Animals ; Bicuculline ; pharmacology ; Disease Models, Animal ; Glycine ; metabolism ; Hyperalgesia ; drug therapy ; etiology ; metabolism ; Imidazoles ; pharmacology ; Inhibitory Postsynaptic Potentials ; drug effects ; physiology ; Male ; Mice, Inbred C57BL ; Neurons ; drug effects ; metabolism ; Neurotransmitter Agents ; pharmacology ; Peripheral Nerve Injuries ; drug therapy ; metabolism ; Phenanthrolines ; pharmacology ; Potassium Channels, Inwardly Rectifying ; antagonists & inhibitors ; metabolism ; Receptors, GABA-A ; metabolism ; Receptors, Glycine ; metabolism ; Strychnine ; pharmacology ; Synaptic Transmission ; drug effects ; physiology ; Tissue Culture Techniques ; Touch

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.
Accidental Falls ; Adult ; Apnea ; Clonazepam ; Gait* ; Genetic Background ; Glycine Plasma Membrane Transport Proteins ; Humans ; Nervous System Diseases ; Noise ; Phenotype* ; Pneumonia, Aspiration ; Receptors, Glycine ; Reflex, Startle ; Sodium ; Stiff-Person Syndrome* ; Wills

OBJECTIVE: The aim of the present study was to perform a subgroup analysis of data from a phase II global, multi-center, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of bitopertin, a glycine reuptake inhibitor that activates N-methyl-D-aspartate receptors by increasing the concentration of glycine in the synaptic cleft, in Japanese and non-Japanese patients with schizophrenia and predominant negative symptoms. METHODS: Patients with schizophrenia and predominant negative symptoms on one or two antipsychotic drugs, including atypical antipsychotic drugs (olanzapine, risperidone, quetiapine, aripiprazole, and paliperidone) as the primary treatment, received bitopertin (10, 30, or 60 mg/day) or placebo once daily for 8 weeks as an add-on treatment. Efficacy was assessed using the Positive and Negative Syndrome Scale (PANSS) negative symptom factor score (NSFS). RESULTS: The efficacy of bitopertin (10 mg and 30 mg) was similar between Japanese and non-Japanese patients. In the bitopertin 60-mg group, no difference from the placebo group was observed in Japanese or non-Japanese patients. The response to placebo was lower in Japanese patients, and there was a trend towards a greater difference in the change in PANSS NSFS between the placebo group and the 10-mg and 30-mg groups among Japanese patients. The safety profile of bitopertin was favorable in Japanese and non-Japanese patients. CONCLUSION: According to this subgroup analysis from a global phase II study of bitopertin, there was no difference in terms of efficacy and safety between Japanese and non-Japanese patients.
Antipsychotic Agents ; Aripiprazole ; Asian Continental Ancestry Group* ; Glycine ; Humans ; Japan ; Quetiapine Fumarate ; Receptors, N-Methyl-D-Aspartate ; Risperidone ; Schizophrenia*

This study aims to detect the expression of metabotropic glutamate receptors (mGluRs) in lung carcinoma A549 cells, and to investigate the effects of mGluR8 and mGluR4 activation on the growth of A549 cells in vitro. The mRNA expression levels of the 8 subtypes of mGluRs in A549 cells were determined by real-time PCR. Immunohistochemistry was used to analyze the protein expression of mGluR4 and mGluR8 in A549 cells and lung tissue sections obtained from lung adenocarcinoma patients. To observe the effects of mGluR8 and mGluR4 activation on the growth of A549 cells, the cultured cells were treated with (S)-3,4-DCPG (an agonist of mGluR8) and VU0155041 (an agonist of mGluR4), respectively, and then the cell viability was analyzed by CCK-8 kit, the percentage of DNA synthesis was detected by EdU incorporation, and the apoptosis of the cells was measured by hoechst 33258 staining and flow cytometry. The results showed that there were low expressions of mGluR1, mGluR5, mGluR6, mGluR7 mRNA, no expression of mGluR2 and mGluR3 mRNA, and high expressions of mGluR8 and mGluR4 mRNA in A549 cells. Accordingly, there were also mGluR4 and mGluR8 protein expressions in the A549 cells and the lung adenocarcinoma tissue sections. VU0155041 had no effect on the growth of A549 cells, but (S)-3,4-DCPG significantly decreased the cells' growth in a dose-dependent manner and increased the apoptosis of the cells. The results revealed a role of mGluR8 in the growth and apoptosis of A549 cells and suggested a potential target for clinical treatment of lung cancer.
Anilides ; pharmacology ; Apoptosis ; Benzoates ; pharmacology ; Cell Cycle ; Cell Line, Tumor ; Cell Proliferation ; Cyclohexanecarboxylic Acids ; pharmacology ; Glycine ; analogs & derivatives ; pharmacology ; Humans ; Lung Neoplasms ; pathology ; Receptors, Metabotropic Glutamate ; physiology

OBJECTIVETo investigate the role of ventrolateral periaqueductal gray (VL-PAG) metabotropic glutamate receptors subtype 7 and 8 (mGluR 7/8) in descending modulation of cardiosomatic motor reflex (CMR) in rats.

METHODSAMN082 (agonist of mGluR 7) and DCPG (agonist of mGluR 8) were injected into the VL-PAG of a rat model of CMR to observe their effects in modulating CMR. The raphe magnus nucleus (NRM) or the gigantocellular reticular nucleus (Gi) was then damaged, and the changes in VL-PAG descending modulation were observed.

RESULTSSelective activation of mGluR 7 of the VL-PAG by AMN082 obviously facilitated capsaicin (CAP)-induced CMR (P<0.05), which was suppressed by DCPG-induced mGluR 8 activation (P<0.05). These facilitatory or inhibitory effects were completely reversed by group III mGluR antagonist MSOP. Damaging the NRM of VL-PAG main relay nucleus did not significantly affect the facilitatory effect produced by AMN082 microinjection (P>0.05), but partially attenuated the inhibitory effect of DCPG microinjection (P<0.05). Both the facilitatory effect of AMN082 and the inhibitory effect of DCPG were reduced obviously after bilateral Gi damage (P<0.05).

CONCLUSIONVL-PAG mGluR 7 and mGluR 8 mediate biphasic regulation of CMR in rats probably through activation of different sub-nuclei and different neurons in the rostroventral medulla.

Animals ; Benzhydryl Compounds ; pharmacology ; Benzoates ; pharmacology ; Glycine ; analogs & derivatives ; pharmacology ; Male ; Medulla Oblongata ; metabolism ; Periaqueductal Gray ; metabolism ; Physical Conditioning, Animal ; Rats ; Rats, Sprague-Dawley ; Receptors, Metabotropic Glutamate ; agonists ; metabolism ; Reflex ; physiology

The downregulation of A-type K+ channels (IA channels) accompanying enhanced somatic excitability can mediate epileptogenic conditions in mammalian central nervous system. As IA channels are dominantly targeted by dendritic and postsynaptic processings during synaptic plasticity, it is presumable that they may act as cellular linkers between synaptic responses and somatic processings under various excitable conditions. In the present study, we electrophysiologically tested if the downregulation of somatic IA channels was sensitive to synaptic activities in young hippocampal neurons. In primarily cultured hippocampal neurons (DIV 6~9), the peak of IA recorded by a whole-cell patch was significantly reduced by high KCl or exogenous glutamate treatment to enhance synaptic activities. However, the pretreatment of MK801 to block synaptic NMDA receptors abolished the glutamate-induced reduction of the IA peak, indicating the necessity of synaptic activation for the reduction of somatic IA. This was again confirmed by glycine treatment, showing a significant reduction of the somatic IA peak. Additionally, the gating property of IA channels was also sensitive to the activation of synaptic NMDA receptors, showing the hyperpolarizing shift in inactivation kinetics. These results suggest that synaptic LTP possibly potentiates somatic excitability via downregulating IA channels in expression and gating kinetics. The consequential changes of somatic excitability following the activity-dependent modulation of synaptic responses may be a series of processings for neuronal functions to determine outputs in memory mechanisms or pathogenic conditions.
Animals ; Central Nervous System ; Dizocilpine Maleate ; Down-Regulation* ; Glutamic Acid ; Glycine ; Kinetics ; Long-Term Potentiation ; Memory ; N-Methylaspartate* ; Neurons* ; Plastics ; Rats* ; Receptors, N-Methyl-D-Aspartate*

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.
Animals ; CA1 Region, Hippocampal ; cytology ; Glycine ; pharmacology ; Patch-Clamp Techniques ; Pyramidal Cells ; drug effects ; Rats ; Receptors, Glycine ; metabolism ; Strychnine ; pharmacology

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.
Animals ; Apoptosis ; Cell Death ; Chick Embryo ; Glycine ; Hand ; Receptors, Glycine