Affinity For GABA Receptors Research Articles

Ozone therapy in multiple disabled children

Multiple disabilities is term for child with several disabilities sensory associated with motor disabilities. Growing number of children are presented with development issues caused by cerebral palsy , autism, learning disabilities, ADHD, Genetic disorder , global delayed development . Problem of this children are multifold and affects the daily life of whole family No such conventional treatment can cure these problems these problems. They are treating specific symptoms of Autism and global delay improve the child functioning and helping them in daily activity . It is ethically correct to take advantage of ozone therapy when the best orthodox treatment has failed . Anecdotal study was done in 47 children ranging from 8months to 12 yrs of age with multiple disabilities . Along with conventional treatment and various therapy like occupational therapy , physio therapy , sensory integration, speech therapy, ozone therapy i.e rectal insufflation (10mcg to 80mcg per kg) ear insufflation (10mcg / 120ml for 5 to 10 mins ) were given. In selected cases S/C injection, vacuum massage, matra basti with Ayurvedic medicated ghrut like “Bhrami Ghruth, Ashwagandha Ghruth, Mahakalyank Ghruth”. The rectal insufflation of ozone is a systemic routed which dissolves quickly in the luminal contents of the bowel, where mucoprotiens and other secretory products with antioxidants activity readily react with ozone to produce reactive oxygen species (ROS) and lipid peroxidation products. These compound penetrate the muscular mucosa and enter the circulation of venous and lymphatic capillaries. This non-invasive technique can be used without risk in pediatric and elderly patients. Ear insufflation through capillaries of ear: it is believed that it is absorbed, it secretes hormone endorphin which gives cool & calm effect which improves the quality of sleep. Vacuum increases the blood flow and ozone can react better and S/C injection improves local blood circulation . Herbal drugs like centella acitica(Brahmi) shows significant improvement in neuron function in areas of the brain associated with learning and memory useful in ADHD. “Withenia Somnifera (Ashwagandh)” shows high affinity for GABA receptors that is helpful in memory loss, anxiety and ADHD “Ghrut” is a detoxifying agent makes the organ soft increases intelligence refine the intellect (dhi), improve the memory(Smruti), increases digestive AGNI ,cools the body and gives synergistic effect with ozone application (Yogwahi) OBSERVATION : 1. Improvement in Alertness, immunity, Digestion 2. Weight Gain 3. Improvement in muscle tone that enables child to perform daily physical activity It is very early to arrive at any conclusion, But results are encouraging and Very Safe

6-Methoxyflavanone attenuates mechanical allodynia and vulvodynia in the streptozotocin-induced diabetic neuropathic pain

Diabetic neuropathy is the most prevalent, persistent and debilitating complication of diabetes mellitus often coupled with vulvodynia that may present as an isolated symptom or as a part of constellation of other neuropathic abnormalities. Flavonoids have selective affinity for GABA receptors and 6-methoxyflavanone (6-MeOF) is a positive allosteric modulator of GABA responses at human recombinant GABAA receptors. GABAergic and opioidergic system inhibition have been shown to facilitate neuropathic pain. 6-MeOF was evaluated for analgesic effect in the hot plate test and streptozotocin-induced diabetic neuropathic pain in female rats using von Frey hairs. The possible involvement of opioidergic and GABAergic mechanisms was investigated using naloxone and pentylenetetrazole (PTZ) antagonists, respectively. The biodistribution of 6-MeOF in plasma and CNS was examined using a validated HPLC/UV analytical method. The binding affinity of 6-MeOF with opioid and GABA receptors was studied using molecular docking simulation approach. 6-MeOF (10 and 30mg/kg) attenuated the acute phasic thermal nociception in the hot plate test while in the case of streptozotocin-induced diabetic neuropathy model, 6-MeOF (10 and 30mg/kg) produced static/dynamic anti-allodynic (increased paw withdrawal threshold and latency) as well as static/dynamic anti-vulvodynic effects (increased flinching response threshold and latency), when compared to the vehicle and standard gabapentin (75mg/kg). In silico studies depicted the preference of 6-MeOF for the delta- and kappa-opioid and GABAA receptors. Moreover, the pharmacokinetic profile revealed a quick appearance of 6-MeOF in the systemic circulation and brain areas with maximum concentration observed after 30min in the amygdala, brain stem and cerebral cortex. 6-MeOF readily crosses the blood brain barrier and may be effective in attenuating the diabetes-induced allodynia as well as vulvodynia, probably through interactions with the GABAergic and opioidergic systems.

Overview of Seizure-Inducing Potential of Doripenem

The seizure-inducing potential of carbapenems has been debated since the introduction of imipenem/cilastatin over 20 years ago. Doripenem is a new carbapenem, recently approved in the US for the treatment of adults with complicated urinary tract infections (cUTI) or complicated intra-abdominal infections (cIAI), and additionally in the EU for nosocomial pneumonia, including ventilator-associated pneumonia. Here, the seizure-inducing potential of doripenem is evaluated, using data from in vitro and in vivo animal studies, doripenem clinical trials and doripenem postmarketing reports of seizures. Animal studies indicate that doripenem has low binding affinity for GABA receptors and does not induce seizures at doses greater than seizure-inducing doses of imipenem or meropenem. In clinical studies of cUTI or cIAI, no seizures were reported in the 1332 patients treated with doripenem (500-mg infusion every 8 hours). In two studies, patients with nosocomial pneumonia were treated with doripenem 500 mg (1- or 4-hour infusion every 8 hours), and the incidence of seizures was lower for doripenem (1.2% [6/485]) than imipenem (3.8% [10/263]) or piperacillin/tazobactam (2.7% [6/221]). For patients with seizure-predisposing conditions, seizures occurred during treatment for 3/193 (1.5%) in doripenem, 1/66 (1.5%) in piperacillin/tazobactam and 6/116 (5.2%) in the imipenem group. The review of data from both clinical trials and postmarketing surveillance supports the low seizure-inducing potential of doripenem. The seizure potential of doripenem should be evaluated further in patients at increased risk for seizure.

Now I know my ABC. A systems neurochemistry and functional metabolomic approach to understanding the GABAergic system

Here, we describe use of a reductionist brain model, the brain tissue slice, to generate snapshots of functional metabolism in response to a pharmacological (GABAergic) perturbation. Tissue slices prepared from Guinea pig cerebral cortex were incubated for 1 h in the presence of [3-13C]-pyruvate and ligands with affinity for GABA receptors. The resultant patterns of 13C flux and metabolite levels were measured by 13C/1H NMR spectroscopy, generating 'metabolic fingerprints' for each ligand. Effects of agonists and effectors at GABA receptors (A, B, and C types) were examined, compared to those of exogenous GABA and evaluated using multivariate statistical models. Data clusterings did not directly correlate with GABA receptor types but produced at least five distinct groups ranked according to their affinity for GABA. As our experimental model retains, to a large extent, the structure and function of normal brain tissue, the generated database can be used to assess GABAergic ligands and make unique inferences relevant to their modes of action in brain.

Synthesis of an anionically substituted nitroindoline-caged GABA reagent that has reduced affinity for GABA receptors

A 7-nitroindolin-1-yl amide of the neuroactive amino acid γ-aminobutryate (GABA) has been synthesised with two phosphate groups attached to the indoline nucleus at 4-alkoxy substituent. The compound is designed to release GABA on a sub-microsecond time scale in response to flash photolysis with near-UV light. The presence of the high negatively charged substituent shows evidence that interaction of the GABA conjugate with ionotropic GABA receptors is much reduced in comparison with an earlier nitroindoline-GABA compound that had no charged groups on the indoline nucleus. In experiments to develop the eventual synthetic route, an unusual reductive cleavage of a TBDMS ether was observed as a significant side reaction during reduction of an indole to an indoline with NaBH 3CN in glacial acetic acid. In the eventual synthetic route, the primary amine of GABA was masked as an azide until the final stage of the synthesis, which overcame significant problems with other forms of amine protection.

Extracellular proton modulates GABAergic synaptic transmission in rat hippocampal CA3 neurons

Acidification, which occurs in some pathological conditions, such as ischemia and hypoxia often induces neurotoxicity. The activation of acid-sensing ion channels (ASICs), which are highly permeable to calcium, has been considered the main target responsible for calcium overload in ischemic/hypoxic brain. However, the influence of extracellular proton on GABAergic synaptic transmission is not well understood. In the rat (aged 6–12 postnatal days) hippocampal CA3 neurons dissociated with an enzyme-free, mechanical method, we show that raising the extracellular pH (to 8.5) or lowering it (to 6.0) significantly increased or decreased, respectively, the frequency and the amplitude of spontaneous inhibitory postsynaptic currents mediated by γ-aminobutyric acid A (GABA A) receptors. Interestingly, these modifications were not altered by amiloride (100 μM, an antagonist for ASICs), tetrodotoxin (0.5 μM, a sodium channel blocker), cadmium (100 μM, a nonselective blocker for voltage-gated calcium channels), or a medium containing low calcium (0.5 mM). Significantly, changes in extracellular pH biphasically altered the peak amplitude of the currents elicited by exogenous GABA in CA3 neurons dissociated with enzyme. Raising the extracellular pH (to 8.5) or lowering (to 6.5) shifted the concentration–response curves of GABA to the left or right, respectively, without altering the maximal responses. These data suggest that proton alters the apparent affinity of GABA receptors for agonist. Thus, extracellular proton modifies GABAergic synaptic transmission both presynaptically and postsynaptically, and this could be independent of ASICs and voltage-gated calcium channels. Our finding may constitute a new mechanism underlying acidification-induced neurotoxicity.

3-Chloropropanoic acid (UMB66): a ligand for the gamma-hydroxybutyric acid receptor lacking a 4-hydroxyl group

Gamma-Hydroxybutyric acid (GHB) has gained in notoriety in recent years due to its association with sexual assaults. GHB is an endogenous ligand for GHB receptors, but its complete pharmacological mechanism of action in vivo remains unclear due to apparent GABAergic components. It has been proposed that the hydroxyl group in the 4-position acts as a hydrogen bond donor to the GHB receptor. Herein we show that 3-chloropropanoic acid possesses significant affinity for the GHB receptor, has no affinity for GABA receptors, and cannot undergo metabolism to GABAergic compounds. UMB66 is thus a selective agent for the study of GHB in vivo. These results, in combination with data from quantum mechanical calculations, suggest that the hydroxyl group of GHB actually acts as a hydrogen bond acceptor in contrast to the currently accepted model. This finding is anticipated to facilitate the rational design of novel agents with selectivity for GHB receptors that may be used to elucidate the mechanism of action of this common drug of abuse.

The rhythmic GABAergic system.

GABA is the major inhibitory neurotransmitter in the mammalian brain, and has been implicated in the regulation of a variety of behavioral functions, including biological rhythms. The focus of this minireview is the rhythmic variation of the central GABAergic system, comprising fluctuations of GABA levels and turnover, GABA receptor affinity and postsynaptic activity on the chloride ionophore in rodent's brain. Neurochemical rhythms correlated with diurnal and circadian changes in several behaviors associated with the GABA(A) receptor, e.g., anxiolysis-related behavior. GABA is considered to be the principal neurotransmitter of the mammalian circadian system, being present in the suprachiasmatic nuclei and the intergeniculate leaflet. Pharmacological manipulations of GABA(A) receptors phase shift circadian rhythms and alter circadian responses to light. Administration of putative modulators of GABA function, like melatonin or neuroactive steroids, affects the timing of biological rhythms. Therefore, not only does the GABAergic system exhibit strong diurnal and circadian variations, but it also serves as one of the key modulators of the circadian apparatus.

Direct Evidence For Diazepam Modulation of GABAA Receptor Microscopic Affinity

Alteration of agonist affinity is a potential mechanism for pharmacological modulation of ligandgated receptor channel function. The time course for receptor activation and current onset is determined by the combined rates for two kinetic transitions that underlie the protein conformations for binding agonist and channel gating. Using ultrafast ligand exchange techniques, we distinguish between these previously difficult to separate events and demonstrate their independent pharmacological modulation. Diazepam, which increases apparent affinity of γ-aminobutyric acid (GABA) to GABAA receptors, was used to examine its effects on GABA binding and ion channel gating of expressed α2β1γ2 receptors from excised outside-out patches of acutely transfected HEK 293 cells. Diazepam increased rates of current onset evoked by low concentrations (<1 mM) but not at saturating GABA concentrations. Furthermore, rates of current decay were not affected during brief applications of GABA, and thus, demonstrated a diazepam specific effect on ligand binding affinity and not channel gating kinetics. However, current decay during and following prolonged GABA applications were altered by diazepam in a fashion similar to that for higher concentrations of GABA which also increased receptor desensitization. These findings and analysis by computer modeling indicated that diazepam likely enhances GABA receptor currents primarily by accelerating GABA association to its receptor at the first agonist binding site. These results provide the first direct physiological evidence for pharmacological modulation of microscopic binding affinity of GABA receptors. Copyright © 1996 Elsevier Science Ltd

GABA, depressants and chloride ions affect the rate of dissociation of 35S-t-butylbicyclophosphorothionate binding

The dissociation of 35S-TBPS was studied from binding sites of rat cerebral cortex. Monophasic dissociation plots became polyphasic and accelerated in the presence of micromolar concentrations of GABA suggesting the involvement of low (or super-low) affinity GABA receptors. The presence of the depressants etazolate, R(-)MPPB and ethanol resulted in similarly accelerated dissociation patterns. In contrast, the convulsants S(+)MPPB and pentamethylenetetrazol did not significantly affect the dissociation of TBPS. Dissociation initiated by dilution was not affected either by an excess of picrotoxin or by varying the equilibrium occupancy of the TBPS sites. These findings rule out the possibility of a kinetic cooperativity for the binding of convulsants. The removal of chloride ions also enhanced the rate of TBPS dissociation. Kinetic heterogeneity of the TBPS binding sites can be interpreted with allosteric interactions mediated by various sites at the GABA receptor complex coupled to different states of the chloride ionophore.

GABA receptor binding and hemodynamic responses to ICV GABA in adult spontaneously hypertensive rats.

Blood pressure and heart rate responses after central administration of GABA (100–1000 μg, ICV) and after ganglionic blockade with hexamethonium (25 mg/kg, i.a.) were compared in conscious 12 week-old spontaneously hypertensive (SH) and age-matched Wistar-Kyoto (WKY) rats. Ganglionic blockade produced an equivalent change in mean arterial pressure between SH and WKY rats. Thus, the total functional sympathetic nervous system contribution to blood pressure is equivalent in these two strains. Intraventricularly-administered GABA produced a greater absolute decrease in mean arterial pressure in the SHR compared to the WKY. However, the percent changes in arterial pressure produced by GABA were not different between these strains. This greater absolute depressor effect of GABA does not appear to be due to differences in GABA receptor binding constants since GABA receptor affinity and number of binding sites were not significantly different in the forebrain, cerebellum or pons-medulla between SH and WKY rats.

The potential use of GABA agonists in psychiatric disorders: Evidence from studies with progabide in animal models and clinical trials

Progabide, a new antiepileptic GABA agonist of moderate affinity for GABA receptors, has been studied in a number of psychiatric disorders and the results compared with the action of this drug in animal models. In an animal model for anxiety (the aversive response to periaqueductal grey stimulation in the rat) progabide had a similar action to that of diazepam. However in clinical trials to date the effect of the GABA agonist was inferior to that of benzodiazepines. As progabide diminishes both the nigrostriatal dopamine neuron activity and the effects of striatal dopamine receptor activation, a trial in schizophrenic patients was undertaken. Progabide was devoid of any evident antipsychotic action. However a certain improvement in responsiveness to the environment and in social interactions was noticed in hebephrenic and schizoaffective syndromes. This lack of antipsychotic effect of progabide may be a reflection of the weak activity of GABA agonists on limbic dopamine neurons. In these various clinical trials a definite improvement of affect and mood was noted in those patients receiving progabide. In clinical trials in depressed patients progabide produces a significant reduction in depressive symptoms, an action similar to that of imipramine both for the global clinical rating and the HRSD. This antidepressant activity is reflected by the action of progabide in behavioural models of depression such as olfactory bulbectomy, learned helplessness and the sleep-wake cycle.

Epimeric cis-decahydroquinoline-5-carboxylic acids: effects on gamma-aminobutyric acid uptake and receptor binding in vitro.

The syntheses for two cis-decahydroquinoline-5-carboxylic acid epimers (1 and 2) which contain the =N(C)3CO2H (gamma-aminobutyric acid; GABA) moiety are described. Both intra-and intermolecular [4 + 2] cycloaddition reactions were employed for the construction of key intermediates. 1H NMR studies provided evidence for the preferred solution conformations of the two diastereomers. Pharmacological studies revealed that these isomers have little affinity for GABA receptors in vitro relative to GABA agonists. However, expected but weak stereoselective activity was observed when these analogues were assessed for their ability to inhibit high-affinity [3H]GABA uptake into rat brain synaptosomes. These data are discussed in light of structure-activity studies of other neurotransmitter analogues, and a preliminary hypothesis based upon conformational analysis is presented to explain the results.

Chronic neuroleptic treatment specifically alters the number of dopamine receptors in rat brain

Trifluoperazine dihydrochloride (2.8–4.0 mg/kg/day) was administered continuously to rats in drinking water for six months. Animals killed at this time exhibited an increase in the number of dopamine receptors in the striatum and mesolimbic area, with a corresponding decrease in affinity (increase in the dissociation constant) for 3H-spiperone binding. In frontal cortex, 3H-spiperone binding to 5-HT receptors indicated no apparent change in numbers of receptors, but a slight increase in the dissociation constant. There was no obvious alteration in 3H-apomorphine binding in the striatum and mesolimbic area, but the individual results were very variable. The number and binding affinity of muscarinic receptors in striatum, mesolimbic area and cerebral cortex as identified by 3H-dexetemide were unchanged. Nor was there any alternation in the number or binding affinity of H-1 receptors identified by 3H-mepyramine, or of α-noradrenergic receptors identified by 3H-WB 4101, in cerebral cortex. The number and binding affinity of GABA receptors in the cerebellum identified by 3H-muscimol also was not altered. Chronic neuroleptic administration to rats appears to alter specifically the number of cerebral dopamine receptors.

Increase in striatal [3H]muscimol binding following intrastriatal injection of kainic acid: a denervation supersensitivity phenomenon.

The effect of intrastriatal microinjection of kainic acid (KA) on specific binding of [3h]muscimol to the particulate fractions obtained from corpus striatum (CS), globus pallidus (GP), substantia nigra (SN), and cerebral cortex (CC) was examined. Seven days after the unilateral intrastriatal microinjection of KA, the amount of specifically bound [3H]muscimol was significantly increased at the injected site, whereas no significant alteration of [3H]muscimol binding was found in GP, SN, or CC. Scatchard analysis of striatal binding revealed that microinjection of KA significantly increased the affinity (KD) of GABA receptors on the injected (lesioned) side of the CS without affecting the total number of binding sites (Bmax) therein. This significant increase in [3H]muscimol binding, however, was eliminated by pretreating particulate fractions from the CS with Triton X-100, a non-ionic detergent. No statistically significant difference in amounts of [3H]muscimol binding was detected when the preparations from the KA-treated and non-treated CS were preincubated with 0.05% Triton X-100, respectively. Scatchard analysis using CS preparations treated with 0.05% Triton X-100 revealed that the affinity of the GABA receptor was increased by treatment with Triton X-100, while the total number of binding sites (Bmax) was unchanged by this treatment. These results suggest that neuronal degeneration produced by KA in vivo and pretreatment of particulate preparations with Triton X-100 in vitro may increase the amount of specifically bound [3H]muscimol to CS preparations by a similar molecular mechanism.