Preclinical studies suggest that the GABA receptor is a potential target for treatment of substance use disorders. Baclofen (BLF), a prototypical GABA receptor agonist, is the only specific GABA receptor agonist available for application in clinical addiction treatment. The nucleus accumbens shell (AcbSh) is a key node in the circuit that controls reward-directed behavior. However, the relationship between GABA receptors in the AcbSh and memory reconsolidation was unclear. The aim of this study was to investigate the effect of intra-AcbSh injection of BLF on the reconsolidation of morphine reward memory. Male C57BL/6J mice were used to establish morphine conditioned place preference (CPP) model and carry out morphine reward memory retrieval and activation experiment. The effects of intra-AcbSh injection of BLF on morphine-induced CPP, reinstatement of CPP and locomotor activity were observed after environmental cues activating morphine reward memory. The results showed that intra-AcbSh injection of BLF (0.06 nmol/0.2 μL/side or 0.12 nmol/0.2 μL/side), rather than vehicle or BLF (0.01 nmol/0.2 μL/side), following morphine reward memory retrieval abolished morphine-induced CPP by disrupting its reconsolidation in mice. Moreover, this effect persisted for more than 14 days, which was not reversed by a morphine priming injection. Furthermore, intra-AcbSh injection of BLF without morphine reward memory retrieval had no effect on morphine-associated reward memory. Interestingly, administration of BLF into the AcbSh had no effect on the locomotor activity of mice during testing phase. Based on these results, we concluded that intra-AcbSh injection of BLF following morphine reward memory could erase morphine-induced CPP by disrupting its reconsolidation. Activating GABA receptor in AcbSh during drug memory reconsolidation may be a potential approach to prevent drug relapse.
Animals ; Baclofen ; administration & dosage ; Conditioning, Classical ; GABA-B Receptor Agonists ; administration & dosage ; Locomotion ; Male ; Memory ; Mice ; Mice, Inbred C57BL ; Morphine ; Nucleus Accumbens ; drug effects ; Opioid-Related Disorders ; Reward

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

OBJECTIVE: Suvorexant is a novel hypnotic drug that does not interact with the conventional γ-aminobutyric acid (GABA)-A receptor. We investigated the method by which suvorexant was introduced in insomnia patients who were taking benzodiazepine receptor agonists (BzRA). METHODS: This was a retrospective study. We extracted clinical data for patients who were prescribed suvorexant and were already using BzRA. The patients were assigned to two groups, the switching and add-on groups. We assessed the suvorexant discontinuation rate at one month after the prescription of the drug. RESULTS: One hundred and nineteen patients were assigned to the switching group, and 109 were assigned to the add-on group. The add-on group exhibited a significantly higher all-cause discontinuation rate than the switching group (odds ratio, 2.7; 95% confidence interval, 1.5 to 5.0; adjusted p < 0.001). Intolerability was a significantly stronger risk factor for suvorexant discontinuation in the add-on group (22.0% vs. 7.6%, p < 0.002), and the most common adverse effect was oversedation. CONCLUSION: Our results show that the add-on of suvorexant increases the frequency of oversedation compared with switching in insomnia patients that are taking BzRA. However, this was only a preliminary retrospective study, and further studies will be required to confirm our findings.
Benzodiazepines* ; Humans ; Methods ; Orexin Receptor Antagonists ; Prescriptions ; Receptors, GABA-A* ; Retrospective Studies* ; Risk Factors ; Sleep Initiation and Maintenance Disorders*

BACKGROUND: Curcumin is traditionally used as an herbal medicine. We explored the efficacy of intrathecal curcumin in relieving both postoperative and inflammatory pain and elucidated the mechanisms of action of curcumin interacting with γ-aminobutyric acid (GABA) and opioid receptors at the spinal level. METHODS: Experimental pain was induced in male Sprague-Dawley rats via paw incision or injection of intraplantar carrageenan. After examination of the effects of intrathecal curcumin on the pain, GABA and opioid receptor antagonists were intrathecally administered to explore the involvement of GABA or opioid receptors on the effect of curcumin. Additionally, the expression levels of the GABA and opioid receptors were assessed. RESULTS: Intrathecal curcumin reduced the withdrawal threshold of both incisional surgery- and carrageenan injection-induced nociception. Intrathecal GABA and opioid receptor antagonists reversed the curcumin-mediated antinociception. Incisional surgery decreased the levels of the GABA receptors mRNA, but little changed the levels of the opioid receptors mRNA. Carrageenan injection increased the levels of the opioid receptors mRNA, but not the GABA receptors mRNA levels. Intrathecal curcumin increased or decreased the levels of GABA receptors mRNA and opioid receptors mRNA in the spinal cords of incised or carrageenan-injected rats, respectively. CONCLUSIONS: Intrathecal curcumin was effective to postoperative and inflammatory pain and such antinociception of curcumin was antagonized by both GABA and opioid receptor antagonists. Also, intrathecal curcumin altered the levels of GABA and opioid receptors. Thus, spinal GABA and opioid receptors may, respectively, be directly or indirectly involved when curcumin alleviates postoperative and inflammatory pain.
Animals ; Carrageenan ; Curcumin ; gamma-Aminobutyric Acid ; Herbal Medicine ; Humans ; Male ; Narcotic Antagonists ; Nociception ; Rats ; Rats, Sprague-Dawley ; Receptors, GABA ; Receptors, Opioid ; RNA, Messenger ; Spinal Cord

Exploring the transition from inter-ictal to ictal epileptiform discharges (IDs) and how GABA receptor-mediated action affects the onset of IDs will enrich our understanding of epileptogenesis and epilepsy treatment. We used Mg-free artificial cerebrospinal fluid (ACSF) to induce epileptiform discharges in juvenile mouse hippocampal slices and used a micro-electrode array to record the discharges. After the slices were exposed to Mg-free ACSF for 10 min-20 min, synchronous recurrent seizure-like events were recorded across the slices, and each event evolved from inter-ictal epileptiform discharges (IIDs) to pre-ictal epileptiform discharges (PIDs), and then to IDs. During the transition from IIDs to PIDs, the duration of discharges increased and the inter-discharge interval decreased. After adding 3 μmol/L of the GABA receptor agonist muscimol, PIDs and IDs disappeared, and IIDs remained. Further, the application of 10 μmol/L muscimol abolished all the epileptiform discharges. When the GABA receptor antagonist bicuculline was applied at 10 μmol/L, IIDs and PIDs disappeared, and IDs remained at decreased intervals. These results indicated that there are dynamic changes in the hippocampal network preceding the onset of IDs, and GABA receptor activity suppresses the transition from IIDs to IDs in juvenile mouse hippocampus.
Animals ; Animals, Newborn ; Bicuculline ; pharmacology ; Disease Models, Animal ; Epilepsy ; pathology ; GABA-A Receptor Agonists ; pharmacology ; GABA-A Receptor Antagonists ; therapeutic use ; Hippocampus ; drug effects ; metabolism ; physiopathology ; In Vitro Techniques ; Magnesium ; metabolism ; pharmacology ; Male ; Membrane Potentials ; drug effects ; Mice ; Mice, Inbred C57BL ; Muscimol ; pharmacology ; Nerve Net ; drug effects ; Receptors, GABA-A ; metabolism

Sinomenium acutum has been long used in the preparations of traditional medicine in Japan, China and Korea for the treatment of various disorders including rheumatism, fever, pulmonary diseases and mood disorders. Recently, it was reported that Sinomenium acutum, has sedative and anxiolytic effects mediated by GABA-ergic systems. These experiments were performed to investigate whether sinomenine (SIN), an alkaloid derived from Sinomenium acutum enhances pentobarbital-induced sleep via γ-aminobutyric acid (GABA)-ergic systems, and modulates sleep architecture in mice. Oral administration of SIN (40 mg/kg) markedly reduced spontaneous locomotor activity, similar to diazepam (a benzodiazepine agonist) in mice. SIN shortened sleep latency, and increased total sleep time in a dose-dependent manner when co-administrated with pentobarbital (42 mg/kg, i.p.). SIN also increased the number of sleeping mice and total sleep time by concomitant administration with the sub-hypnotic dosage of pentobarbital (28 mg/kg, i.p.). SIN reduced the number of sleep-wake cycles, and increased total sleep time and non-rapid eye movement (NREM) sleep. In addition, SIN also increased chloride influx in the primary cultured hypothalamic neuronal cells. Furthermore, protein overexpression of glutamic acid decarboxylase (GAD(65/67)) and GABA(A) receptor subunits by western blot were found, being activated by SIN. In conclusion, SIN augments pentobarbital-induced sleeping behaviors through GABA(A)-ergic systems, and increased NREM sleep. It could be a candidate for the treatment of insomnia.
Administration, Oral ; Animals ; Anti-Anxiety Agents ; Benzodiazepines ; Blotting, Western ; China ; Diazepam ; Eye Movements* ; Fever ; Glutamate Decarboxylase ; Japan ; Korea ; Lung Diseases ; Medicine, Traditional ; Mice ; Mood Disorders ; Motor Activity ; Neurons ; Pentobarbital ; Receptors, GABA-A ; Rheumatic Diseases ; Rodentia* ; Sinomenium* ; Sleep Initiation and Maintenance Disorders

Stress and emotion are associated with several illnesses from headaches to heart diseases and immune deficiencies to central nervous system. Terminalia arjuna has been referred as traditional Indian medicine for several ailments. The present study aimed to elucidate the effect of T. arjuna bark extract (TA) against picrotoxin-induced anxiety. Forty two male Balb/c mice were randomly divided into six experimental groups (n = 7): control, diazepam (1.5 mg·kg), picrotoxin (1 mg·kg) and three TA treatemt groups (25, 50, and 100 mg/kg). Behavioral paradigms and PCR studies were performed to determine the effect of TA against picrotoxin-induced anxiety. The results showed that TA supplementation increased locomotion towards open arm (EPM) and illuminated area (light-dark box test), and increased rearing frequency (open field test) in a dose dependent manner, compared to picrotoxin (P < 0.05). Furthermore, TA increased number of licks and shocks in Vogel's conflict. PCR studies showed an up-regulation of several genes, such as BDNF, IP, DL, CREB, GABA, SOD, GPx, and GR in TA administered groups. In conclusion, alcoholic extract of TA bark showed protective activity against picrotoxin in mice by modulation of genes related to synaptic plasticity, neurotransmitters, and antioxidant enzymes.
Animals ; Antioxidants ; metabolism ; Anxiety Disorders ; drug therapy ; genetics ; metabolism ; psychology ; Brain-Derived Neurotrophic Factor ; genetics ; metabolism ; Dopamine Agents ; administration & dosage ; GABA Agents ; administration & dosage ; Glutathione Peroxidase ; genetics ; metabolism ; Humans ; Male ; Mice ; Mice, Inbred BALB C ; Neuronal Plasticity ; drug effects ; Neurotransmitter Agents ; metabolism ; Phytotherapy ; Picrotoxin ; adverse effects ; Plant Bark ; chemistry ; Plant Extracts ; administration & dosage ; Serotonin Agents ; administration & dosage ; Superoxide Dismutase-1 ; genetics ; metabolism ; Terminalia ; chemistry

Type A γ-aminobutyric acid receptors (GABAAR) and N-methyl-D-aspartate receptors (NMDAR) are the major inhibitory and excitatory receptors in the central nervous system, respectively. Co-expression of the receptors in the synapse may lead to functional influence between receptors, namely receptor interaction. The interactions between GABAAR and NMDAR can be either positive or negative. However, the mechanisms of interaction between the two receptors remain poorly understood, and potential mechanisms include (1) through a second messenger; (2) by receptors trafficking; (3) by direct interaction; (4) by a third receptor-mediation. Dopamine is the most abundant catecholamine neurotransmitter in the brain, and its receptors, dopamine receptors (DR) can activate multiple signaling pathways. Earlier studies on the interaction between DR and GABAAR/NMDAR have shown some underlying mechanisms, suggesting that DR could mediate the interaction between GABAAR and NMDAR. This paper summarized some recent progresses in the studies of the interaction between DR and NMDAR/GABAAR, providing a further understanding on the interaction between NMDAR and GABAAR mediated by DR.
Animals ; Dopamine ; Neurotransmitter Agents ; Receptors, Dopamine ; Receptors, GABA-A ; Receptors, N-Methyl-D-Aspartate ; Signal Transduction ; Synapses

Etifoxine (etafenoxine, Stresam(R)) is a non-benzodiazepine anxiolytic with an anticonvulsant effect. It was developed in the 1960s for anxiety disorders and is currently being studied for its ability to promote peripheral nerve healing and to treat chemotherapy-induced pain. In addition to being mediated by GABA(A)alpha2 receptors like benzodiazepines, etifoxine appears to produce anxiolytic effects directly by binding to beta2 or beta3 subunits of the GABA(A) receptor complex. It also modulates GABA(A) receptors indirectly via stimulation of neurosteroid production after etifoxine binds to the 18 kDa translocator protein (TSPO) of the outer mitochondrial membrane in the central and peripheral nervous systems, previously known as the peripheral benzodiazepine receptor (PBR). Therefore, the effects of etifoxine are not completely reversed by the benzodiazepine antagonist flumazenil. Etifoxine is used for various emotional and bodily reactions followed by anxiety. It is contraindicated in situations such as shock, severely impaired liver or kidney function, and severe respiratory failure. The average dosage is 150 mg per day for no more than 12 weeks. The most common adverse effect is drowsiness at the initial stage. It does not usually cause any withdrawal syndromes. In conclusion, etifoxine shows less adverse effects of anterograde amnesia, sedation, impaired psychomotor performance, and withdrawal syndromes than those of benzodiazepines. It potentiates GABA(A) receptor-function by a direct allosteric effect and by an indirect mechanism involving the activation of TSPO. It seems promising that non-benzodiazepine anxiolytics including etifoxine will replenish shortcomings of benzodiazepines and selective serotonin reuptake inhibitors according to animated studies related to TSPO.
Amnesia, Anterograde ; Anti-Anxiety Agents ; Anticonvulsants ; Anxiety Disorders ; Anxiety* ; Benzodiazepines ; Flumazenil ; Humans ; Kidney ; Liver ; Mitochondrial Membranes ; Nerve Regeneration ; Neuralgia ; Neurotransmitter Agents ; Peripheral Nerves ; Peripheral Nervous System ; Psychomotor Performance ; Receptors, GABA-A ; Respiratory Insufficiency ; Serotonin Uptake Inhibitors ; Shock ; Sleep Stages

The present study was designed to investigate the inhibitory effects of intravenous general anesthetic propofol (0.1-3.0 mmol/L) on excitatory synaptic transmission in supraoptic nucleus (SON) neurons of rats, and to explore the underlying mechanisms by using intracellular recording technique and hypothalamic slice preparation. It was observed that stimulation of the dorsolateral region of SON could elicit the postsynaptic potentials (PSPs) in SON neurons. Of the 8 tested SON neurons, the PSPs of 7 (88%, 7/8) neurons were decreased by propofol in a concentration-dependent manner, in terms of the PSPs' amplitude (P < 0.01), area under curve, duration, half-width and 10%-90% decay time (P < 0.05). The PSPs were completely and reversibly abolished by 1.0 mmol/L propofol at 2 out of 7 tested cells. The depolarization responses induced by pressure ejection of exogenous glutamate were reversibly and concentration-dependently decreased by bath application of propofol. The PSPs and glutamate-induced responses recorded simultaneously were reversibly and concentration-dependently decreased by propofol, but 0.3 mmol/L propofol only abolished PSPs. The excitatory postsynaptic potentials (EPSPs) of 7 cells increased in the condition of picrotoxin (30 µmol/L, a GABA(A) receptor antagonist) pretreatment. On this basis, the inhibitory effects of propofol on EPSPs were decreased. These data indicate that the presynaptic and postsynaptic mechanisms may be both involved in the inhibitory effects of propofol on excitatory synaptic transmission in SON neurons. The inhibitory effects of propofol on excitatory synaptic transmission of SON neurons may be related to the activation of GABA(A) receptors, but at a high concentration, propofol may also act directly on glutamate receptors.
Anesthetics, Intravenous ; pharmacology ; Animals ; Excitatory Postsynaptic Potentials ; drug effects ; GABA-A Receptor Antagonists ; pharmacology ; Glutamic Acid ; pharmacology ; In Vitro Techniques ; Neurons ; drug effects ; Propofol ; pharmacology ; Rats ; Receptors, Glutamate ; metabolism ; Supraoptic Nucleus ; cytology