Gamma-butyric Acid Research Articles

Exposure to the environmentally relevant fungicide Maneb: Studying toxicity in the soil nematode Caenorhabditis elegans

Maneb is a manganese-containing ethylene bisdithiocarbamate fungicide and is still commonly used as no cases of resistance have been documented. However, studies have shown that Maneb exposure has neurodegenerative potential in mammals, resulting in symptoms affecting the motor system. Despite its extensive use, structural elucidation of Maneb has only recently been accomplished by our group. This study aimed to examine the bioavailability of Maneb, the quantification of oxidative stress-related endpoints and neurotransmitters employing pure Maneb, its metabolites and structural analogues, in the model organism Caenorhabditis elegans. Exposure to Maneb did not increase the bioavailability of Mn compared to manganese chloride, although Maneb was about 8 times more toxic with regard to lethality. Maneb generated not significantly reactive oxygen and nitrogen species (RONS) but decreased the ATP level while increasing the amount of glutathione and its oxidized form in a dose-dependent manner. Nevertheless, an alteration in the neurotransmitter homeostasis of dopamine, acetylcholine, and gamma-butyric acid (GABA) was observed as well as morphological changes in the dopaminergic neurons upon Maneb exposure, which underlines the assumption of the neurotoxic potential of Maneb. This study showed that Maneb exhibits effects based on a combined interaction of the ligand and manganese.

QSAR, molecular docking, and molecular designs of some anti-epilepsy compounds

Epilepsy is a non-communicable central nervous system (CNS) disease that accounts for approximately 0.8–1.2 % of the global population at any time. The hyper-activities of gamma butyric acid aminotransferase (GABAAT) enzyme have been confirmed to be largely responsible for seizure/epilepsy. Because of this special function, the GABAAT enzyme has been the main target of many anti-epilepsy drugs (AEDs). To date, many discovered AEDs have not eradicated this neurological disease. Since experimental determinations of modern drugs are usually costly and sometimes non-eco-friendly, in-silco quantitative structure–activity relationship (QSAR)-machine learning, docking and pharmacokinetics (PMK) techniques were used to design and test the oral bio-availabilities of all the designed AEDs. QSAR models were generated, and the predictive properties of R2int = 0.9827, R2ext = 0.9407, and R2adj of 0.9667 indicate the evidence that the developed model was not by chance. Six (6) new AEDs were newly designed, and they were found to have better anti-epileptic activities values of 2.146799, 2.224866, 2.31479, 2.450313, 2.301474, and 2.618303 than the standard AED, Vigabatrin (0.40672). Also, the docked new compounds shows excellent binding energies of −127.001, −129.071, −130.515, −126.881, −130.771, and −126.974 kcal/mol compared to the referenced AED (−76.9173 kcal/mol). The PMK and absorption, distribution, metabolism, excretion, and toxicity (ADMET) investigations also revealed that all the designed compounds were found to be bio-available for human administration. 'Therefore, the newly designed analogues (AEDs) could be considered as potential drug candidates for the treatment of epilepsy.

IN SILICO STUDY OF Stachytarpheta jamaicensis ACTIVE COMPOUNDS AS ANTIBACTERIAL MATERIAL

Background: Stachytarpheta jamaicensis is a wild plant from the Verbenanceae family that grows in tropical areas such as Indonesia. S. jamaecensis extract was proven to contain secondary metabolite compounds such as flavonoids, phenols, saponins, tannins and terpenoids. The active compound of S. jamaecensis can be used as a drug candidate in the medicine field, especially as an antibacterial compound. One of the first steps in predicting the effectiveness of these compounds can be done through in-Silico studies with molecular docking. Objective: This study aims to evaluate the interaction of active compound S. jamaecensis with bacterial proteins through an in silico study. Methods: Using in silico method with computational docking analysis on seven active compounds of S. jamaecensis namely apigenin, luteolin, chlorogenic acid, gamma butyric acid, dopamine, ipolamide and geraniol, as well as two antibacterial drugs (metronidazole and chlorhexidine) as comparisons bound with bacterial cell wall protein, namely Glucosamine-6-phosphate synthase (G1mS). Docking in silico uses Autodock Vina, which is integrated with PyRx 8.0 and visualized using Discovery Studio Visualizer v19.1.0.18287 (2019 version) with data presentation based on docking scores. Conclusion: The best binding affinity score has been the luteolin-G1mS complex with a binding affinity value of -10.8 kcal/mol and was the highest value compared to the comparison ligand binding and the binding of other active compounds of S. jamaecensis.

Characteristics of Sunsik, a Cereal-Based Ready-to-Drink Korean Beverage, with Added Germinated Wheat and Herbal Plant Extract.

The purpose of this study was to develop a formulation of Sunsik with improved health benefits by adding germinated wheat (GW) and herbal plant extract (HPE) using a response surface methodology (RSM). The central composite experimental design (CCD) was used to evaluate the effects of Sunsik with added HPE (2–4%) and GW (10–20%) on total phenolic content (TPC), total flavonoid content (TFC), Trolox equivalent antioxidant capacity (TEAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, gamma butyric acid (GABA) content, total color changes (△E), browning index (BI), water absorption index (WAI), and water solubility index (WSI). As a result of the CCD, the independent and dependent variables were fitted by the second-order polynomial equation, and the lack of fit for response surface models was not significant except in relation to WSI. The GABA content, TPC, and TEAC were more adequate for a linear model than for a quadratic model, and they might be affected by GW rather than HPE. Alternatively, the TFC, DPPH radical scavenging capacity, WAI, WSI, △E, and BI were fitted with quadratic models. The optimum formulation that could improve antioxidant and physicochemical properties was Sunsik with 3.5% and 20% added HPE and GW, respectively.

Formulation and Evaluation of fixed dose combination of Nootropic drugs

Cognitive functions are the critical brain functions responsible for the effective learning and understanding in the humans. They are responsible for various functions like attention, memory, reasoning and in turn helps to improve knowledge. Cognitive impairment is majorly seen in elderly as the brain is prone to neuro degradation. It may also occur in young adults due to poor diet or exercise. Improving cognition is of utmost importance and can be done by the use of cognition enhancers like Nootropics. This class of drugs is said to act by various mechanisms, which in turn leads to the betterment of the neurotransmission in the brain. They may act on acetylcholine, Gamma Butyric Acid, on the beta amyloid receptor or on NMDA. This research emphasis on the enhancement of cognition along with treating various neurodegenerative diseases like dementia, Alzheimer’s or Parkinson’s. Nootropic drugs are chosen for this formulation as they exhibit a rationale in combination with each other since they follow distinctive route of mechanism to treat the diseases. They also show action by preventing the worsening of the disease and by curing the disease. Nootropics are known to have low toxicity leading to their wide acceptance and research. As compared to other combination of nootropic, in this combination, the side effects are reduced of one in presence of the other and show a much higher bioavailability. They cross the blood brain barrier and central nervous system half-life is longer as compared to the systemic half-life owing to their efficacy and superiority over other nootropics when it comes to treating cognition Fixed dose combination of these nootropic drugs is desired and the dose can’t be varied as they no longer show their effect if not used in the exact dose required. The dosage of this varied drug depends on the severity of the disease and patient condition. The research has helped to achieve the reduction in the total tablet mass from 1500 mg to 1420 mg with the use of few excipients. This made it easier for patients to swallow the tablet easily due to an oval shape of the tablet formulation.

Curcumin alleviates colistin-induced nephrotoxicity and neurotoxicity in rats via attenuation of oxidative stress, inflammation and apoptosis

Colistin is an effective antibiotic against multidrug-resistant (MDR) gram-negative bacterial infections; however, nephrotoxic and neurotoxic effects are fundamental dose-limiting factors for this treatment. This study was conducted to assess the potential protective effects of curcumin, a phenolic constituent of turmeric, against colistin-induced nephrotoxicity and neurotoxicity, and the possible mechanisms underlying any effect. Twenty-four adult male albino rats were randomly classified into 4 equal groups; the control group (orally received saline solution), the curcumin-treated group (orally administered 200 mg curcumin/kg/day), the colistin-treated group (IP administered 300,000 IU colistin/kg/day) and the concurrent group (orally received 200 mg curcumin/kg/day concurrently with colistin injection); all rats were treated for 6 successive days. Colistin administration significantly increased serum creatinine, urea and uric acid levels as well as brain gamma butyric acid (GABA) concentrations. In renal and brain tissues, colistin significantly increased malondialdehyde (MDA), nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and caspase-3 expression levels. In addition, colistin significantly decreased catalase (CAT), glutathione (GSH), and B-cell lymphoma 2 (Bcl-2) expressions. Curcumin administration in colistin-treated rats partially restored each of these altered biochemical, antioxidant, inflammatory and apoptotic markers. Histopathological changes in renal and brain tissues were also alleviated by curcumin co-treatment. Our study reveals a critical role of oxidative damage, inflammation and apoptosis in colistin-induced nephrotoxicity and neurotoxicity and showed that they were markedly ameliorated by curcumin co-administration. Therefore, curcumin could represent a promising agent for prevention of colistin-induced nephrotoxicity and neurotoxicity.

Propriétés pharmacologiques de la vortioxetine et leurs conséquences pré-cliniques

Selective Serotonin Reuptake Inhibitors (SSRIs) are extensively used for the treatment of major depressive disorder (MDD). SSRIs are defined as indirect receptor agonists since the activation of postsynaptic receptors is a consequence of an increase in extracellular concentrations of serotonin (5-HT) mediated by the blockade of serotonin transporter. The activation of some serotoninergic receptors (5-HT1A, post-synaptic, 5-HT1B post-synaptic, 5-HT2B, and 5-HT4), but not all (5-HT1A, pre-synaptic, 5-HT1B pre-synaptic, 5-HT2A, 5-HT2C, 5-HT3, and probably 5-HT6), induces anxiolytic/antidepressive - like effects. Targetting specifically some of them could potentially improve the onset of action and/or efficacy and/or prevent MD relapse. Vortioxetine (Brintellix, 1- [2-(2,4-dimethylphenyl-sulfanyl)-phenyl]-piperazine) is a novel multi-target antidepressant drug approved by the Food and Drug Administration (FDA) and by European Medicines Agency. Its properties are markedly different from the extensively prescribed SSRIs. Compared to the SSRIs, vortioxetine is defined as a multimodal antidepressant drug since it is not only a serotonin reuptake inhibitor, but also a 5-HT1D, 5-HT3, 5-HT7 receptor antagonist, 5-HT1B receptor partial agonist and 5-HT1A receptor agonist. This specific pharmacological profile enables vortioxetine to affect not only the serotoninergic and noradrenergic systems, but also the histaminergic, cholinergic, gamma-butyric acid (GABA) ergic and glutamatergic ones. Thus, vortioxetine not only induces antidepressant-like or anxiolytic-like activity but also improves cognitive parameters in several animal models. Indeed, vortioxetine was shown to improve working memory, episodic memory, cognitive flexibility and spatial memory in young adult rodents and also in old animal models. These specific effects of the vortioxetine are of interest considering that cognitive dysfunction is a common comorbidity to MDD. Altogether, even though this molecule still needs to be investigated further, especially in the insufficient-response to antidepressant drugs, vortioxetine is already an innovative therapeutic option for the treatment of major depression.

Regional distribution of serotonergic receptors: a systems neuroscience perspective on the downstream effects of the multimodal-acting antidepressant vortioxetine on excitatory and inhibitory neurotransmission.

Previous work from this laboratory hypothesized that the multimodal antidepressant vortioxetine enhances cognitive function through a complex mechanism, using serotonergic (5-hydroxytryptamine, 5-HT) receptor actions to modulate gamma-butyric acid (GABA) and glutamate neurotransmission in key brain regions like the prefrontal cortex (PFC) and hippocampus. However, serotonergic receptors have circumscribed expression patterns, and therefore vortioxetine's effects on GABA and glutamate neurotransmission will probably be regionally selective. In this article, we attempt to develop a conceptual framework in which the effects of 5-HT, selective serotonin reuptake inhibitors (SSRIs), and vortioxetine on GABA and glutamate neurotransmission can be understood in the PFC and striatum-2 regions with roles in cognition and substantially different 5-HT receptor expression patterns. Thus, we review the anatomy of the neuronal microcircuitry in the PFC and striatum, anatomical data on 5-HT receptor expression within these microcircuits, and electrophysiological evidence on the effects of 5-HT on the behavior of each cell type. This analysis suggests that 5-HT and SSRIs will have markedly different effects within the PFC, where they will induce mixed effects on GABA and glutamate neurotransmission, compared to the striatum, where they will enhance GABAergic interneuron activity and drive down the activity of medium spiny neurons. Vortioxetine is expected to reduce GABAergic interneuron activity in the PFC and concomitantly increase cortical pyramidal neuron firing. However in the striatum, vortioxetine is expected to increase activity at GABAergic interneurons and have mixed excitatory and inhibitory effects in medium spiny neurons. Thus the conceptual framework developed here suggests that vortioxetine will have regionally selective effects on GABA and glutamate neurotransmission.

Brain region-specific perfluoroalkylated sulfonate (PFSA) and carboxylic acid (PFCA) accumulation and neurochemical biomarker Responses in east Greenland polar Bears (Ursus maritimus)

Perfluoroalkyl substances (PFASs) is a growing class of contaminants in the Arctic environment, and include the established perfluorinated sulfonates (PFSAs; especially perfluorooctane sulfonate (PFOS)) and carboxylic acids (PFCAs). PFSAs and PFCAs of varying chain length have been reported to bioaccumulate in lipid rich tissues of the brain among other tissues such as liver, and can reach high concentrations in top predators including the polar bear. PFCA and PFSA bioaccummulation in the brain has the potential to pose neurotoxic effects and therefore we conducted a study to investigate if variations in neurochemical transmitter systems i.e. the cholinergic, glutaminergic, dopaminergic and GABAergic, could be related to brain-specific bioaccumulation of PFASs in East Greenland polar bears. Nine brain regions from nine polar bears were analyzed for enzyme activity (monoamine oxidase (MAO), acetylcholinesterase (AChE) and glutamine synthetase (GS)) and receptor density (dopamine-2 (D2), muscarinic cholinergic (mAChR) and gamma-butyric acid type A (GABA-A)) along with PFSA and PFCA concentrations. Average brain ∑PFSA concentration was 25ng/g ww where PFOS accounted for 91%. Average ∑PFCA concentration was 88ng/g ww where PFUnDA, PFDoDA and PFTrDA combined accounted for 79%. The highest concentrations of PFASs were measured in brain stem, cerebellum and hippocampus. Correlative analyses were performed both across and within brain regions. Significant positive correlations were found between PFASs and MAO activity in occipital lobe (e.g. ∑PFCA; rp=0.83, p=0.041, n=6) and across brain regions (e.g. ∑PFCA; rp=0.47, p=0.001, ∑PFSA; rp=0.44, p>0.001; n=50). GABA-A receptor density was positively correlated with two PFASs across brain regions (PFOS; rp=0.33, p=0.02 and PFDoDA; rp=0.34, p=0.014; n=52). Significant negative correlations were found between mAChR density and PFASs in cerebellum (e.g. ∑PFCA; rp=−0.95, p=0.013, n=5) and across brain regions (e.g. ∑PFCA; rp=−0.40, p=0.003, ∑PFSA; rp=−0.37, p=0.007; n=52). AChE activity and D2 density were negatively correlated with single PFCAs in several brain regions, whereas GS activity was positively correlated with PFASs primarily in occipital lobe. Results from the present study support the hypothesis that PFAS concentrations in polar bears from East Greenland have exceeded the threshold limits for neurochemical alterations. It is not known whether the observed alterations in neurochemical signaling are currently having negative effects on neurochemistry in East Greenland polar bears. However given the importance of these systems in cognitive processes and motor function, the present results indicate an urgent need for a better understanding of neurochemical effects of PFAS exposure to wildlife.

Effects of 20-OH ecdysone, a spinach (Spinacia oleracea) derived steroid, on metabolic and temperature regulatory parameters

Ecdysteroids have protein anabolic effects and spinach (spinacia oleracea) derived β-ecdysone prevents osteoporosis and deterioration of joint cartilage tissue in ovariectomized (ovx) rats [1,2]. It is devoid of estrogens or androgenic properties. In the present study we investigated the effects of Ecd on lipids and oral glucose tolerance test. Ecd augments effects of gamma butyric acid (GABA) in neurons and since GABA-ergic drugs are effective to ameliorate hot flashes in climacteric women, we also investigated the effects of β-ecdysone on hot flashes utilizing a newly developed technique to measure skin temperature in freely moving ovx animals. Rats were either fed with soy free food or with Ecd containing food (18mg/animal/day for 3 months). An oral glucose tolerance test was performed 4 weeks after ovx. Ecd significantly reduced serum triglycerides, total cholesterol and serum LDL but not HDL concentrations. Basal serum glucose concentrations were lower in Ecd treated animals than in the ovx controls and remained significantly lower following intragastric glucose application. Skin temperature in ovx animals showed pulses (hot flashes) every 20–40 minutes which were not seen in intact animals and Ecd treated ovx animals. We conclude that the Ecd treatment has beneficial effects of serum lipids which may be used in the human to prevent arteriosclerosis. Furthermore, Ecd prevents hot flashes which may be useful in the treatment of climacteric complaints of women.

Divalproex Sodium Reduces Overall Aggression in Youth at High Risk for Bipolar Disorder

The psychopharmacology of aggression in youth is relatively unexplored, even though such maladaptive aggression manifests across many different diagnoses. This study was a 12-week, open-label trial with divalproex sodium (DVPX) in 24 bipolar offspring 6-18 years of age (mean age = 11.3 years; 17 boys) with mixed diagnoses of major depression, cyclothymia, attention-deficit/hyperactivity disorder (ADHD), and oppositional defiant disorder (ODD). The Overt Aggression Scale (OAS) was used to measure aggression in 4-week intervals. We measured serum gamma-butyric acid (GABA) and glutamate levels at baseline and week 12. Seventy-one percent of evaluable subjects were considered responders to DVPX treatment by the OAS. There was a significant correlation between the Young Mania Rating Scale (YMRS) and OAS scores at week 0 (p = 0.036) and week 12 (p = 0.025). Serum DVPX level did not correlate with treatment response. These youths who are at high risk for bipolar disorder experienced an overall decrease in aggressive behavior in response to DVPX. Age or gender did not predict a positive response to DVPX. This study is the first report of treatment efficacy of a mood stabilizer for aggression in youth at high risk for bipolar disorder.

Pulses, patterns and paths: neurobiology of acoustic behaviour in crickets

Crickets use acoustic communication for pair formation. Males sing with rhythmical movements of their wings and the mute females approach the singing males by phonotaxis. Females walking on a trackball rapidly steer towards single sound pulses when exposed to split-song paradigms. Their walking path emerges from consecutive reactive steering responses, which show no temporal selectivity. Temporal pattern recognition is tuned to the species-specific syllable rate and gradually changes the gain of auditory steering. If pattern recognition is based on instantaneous discharge rate coding, then the tuning to the species-specific song pattern may already be present at the level of thoracic interneurons. During the processing of song patterns, changes in cytosolic Ca(2+ )concentrations occur in phase with the chirp rhythm in the local auditory interneurone. Male singing behaviour is controlled by command neurons descending from the brain. The neuropil controlling singing behaviour is located in the anterior protocerebrum next to the mushroom bodies. Singing behaviour is released by injection of cholinergic agonists and inhibited by gamma-butyric acid (GABA). During singing, the sensitivity of the peripheral auditory system remains unchanged but a corollary discharge inhibits auditory processing in afferents and interneurons within the prothoracic auditory neuropil and prevents the auditory neurons from desensitisation.

Pharmacological Modulation of Plasticity

Cortical plasticity plays an important role in learning. Understanding of the mechanisms of plasticity would facilitate strategies to improve learning. CNS active drugs can modify plasticity and learning. Here we tested the effects of neuromodulators [dopamine (DA), norepinephrine (NE), serotonin, acetylcholine ACH)] and, in a different series of experiments, the effects of antiepileptic drugs (AED) on associative long-term potentiation (LTP)-like plasticity and motor learning in eight healthy subjects. LTP was induced by paired associative stimulation (Stefan et al. Brain 2000; 123: 572). Motor learning was investigated in a repeated thumb movement practice protocol (Classen et al. J Neurophysiol 1998; 79: 1117). Single oral doses of the following drugs were tested in a placebo-controlled double-blind crossover design. Neuromodulators: 2mg of cabergoline (DA agonist), 2.5mg of haloperidol (DA antagonist), 40mg of methylphenidate (indirect DA and NE agonist), 1mg of prazosine (NE antagonist), 100mg of sertraline (selective serotonin reuptake inhibitor), 8mg of biperiden (ACH antagonist) and 40mg of tacrine (ACH agonist). AED: 15mg of tiagabine (TGB), 20mg of diazepam (DZP), 1100mg of gabapentin, 3600mg of pirazetam, 300mg of lamotrigine, 100mg of topiramate, and 3000mg of levetiracetam (LEV). Drugs were tested in separate sessions at least one week apart in pseudo-randomized and balanced order. LTP and motor learning were enhanced by cabergoline and methylphenidate, but depressed by haloperidol, prazosine and biperiden. Tacrine had no effect on LTP but enhanced motor learning. LTP was depressed by those AED which enhance gamma-butyric acid (GABA) dependent inhibition (TGB, DZP, in addition LEV) while other AED had no significant effect. The testing of effects of AED on motor learning is work in progress. In conclusion, manipulation of neuromodulatory systems leads to enhancement or depression of LTP and motor learning in the human motor cortex. The congruence of neuromodulatory effects on LTP and motor learning suggests that these two processes share common mechanisms. Neuromodulators may be used to guide cortical plasticity in humans. GABAergic AED interfere negatively with LTP induction and may therefore be detrimental in LTP-dependent learning.

Simultaneous high-performance liquid chromatographic determination of SCH 59884 (phosphate ester prodrug of SCH 56592), SCH 207962 and SCH 56592 in dog plasma.

SCH 59884 is an IV prodrug of SCH 56592, the broad-spectrum azole antifungal agent that is active both orally and intravenously in animal models of infection. SCH 56592 is in phase III clinical trials for the treatment of serious systemic fungal infections. SCH 59884 is a carboxylate ester of SCH 56592 with gamma-butyric acid phosphate. Following IV administration of SCH 59884, the compound is rapidly dephosphorylated to SCH 207962 which is then hydrolyzed to SCH 56592. A high-performance liquid chromatographic (HPLC) method was developed for the simultaneous determination of SCH 59884, SCH 207962 and SCH 56592 in plasma of dogs, a species used for safety evaluation. The HPLC analysis involved protein precipitation with methanol followed by separation on a C-18 column and quantitation by UV absorbance at 260 nm. The lower limits of quantification were 0.1 microg/ml for SCH 59884 and 0.05 microg/ml for SCH 207962 and SCH 56592 in dog plasma. The linearity for the three compounds was satisfactory as indicated by correlation coefficients (r) of >0.98, back-calculated concentrations and visual examination of the calibration curves. The precision and accuracy were satisfactory as shown by coefficients of variation (CV) ranging from 2.4 to 10.6%, and bias values ranging from -8.4 to 13.3%. Moreover, SCH 59884 and SCH 207962 were stable in dog plasma after being subjected to three freeze-thaw cycles. SCH 56592 had been shown earlier to be stable under these conditions. The assay was shown to be specific, accurate, precise, and reliable for use in pharmacokinetic and toxicokinetic studies.

Inhibitory control of synaptic activity in goldfish Mb bipolar cell terminals visualized by FM1-43

To investigate the physiology and plasticity of mixed rod-cone ON-bipolar cells (Mb) in the goldfish retina, we established a slice preparation which allows us to optically monitor the synaptic activity of bipolar cell axon terminals. We used the styryl dye FM1-43 which is incorporated into active axon terminals due to synaptic vesicle cycling and thus reflects synaptic activity. Different activity states of the axon terminals were revealed when slices prepared from light-adapted retinae were incubated in the presence of FM1-43 under various conditions. Depolarizing high K+ Ringer (50 mM) and the gamma-butyric acid (GABA) antagonist bicuculline (100 microM) resulted in more than two-fold increase in the number of stained terminals compared to slices stained in normal Ringer. In contrast, GABA treatment (0.5 mM) reduced the frequency of stained terminals. Thus, in light-adapted retinal slices the synaptic activity of Mb axon terminals can be modulated towards higher and lower activity states. The fact that the GABA antagonist bicuculline had similar effects as stimulatory high K+ Ringer suggests that inhibitory control is an important component in the regulation of synaptic activity and transmitter release in Mb terminals.

Effects of Gamma-Butyric Acid on the Release of Thyrotropin-releasing Hormone from the Rat Retinain vitro

Effects of gamma-butyric acid (GABA) on the release of thyrotropin-releasing hormone (TRH) from the rat retina in vitro were studied. The rat retina was incubated in medium 199 (pH 7.4) with 1.0 mg/ml of bacitracin and 100 micrograms/ml of ascorbic acid (medium). The amount of TRH release into the medium was measured by radioimmunoassay. The TRH release from the rat retina was inhibited significantly in a dose-related manner with the addition of GABA, but not with bicuculline. The inhibitory effect of GABA on TRH release from the retina was blocked by adding bicuculline to the medium. The findings suggest that the GABAergic system inhibits TRH release from the rat retina in vitro.

Glycine-directed peptide amidation: presence in rat brain of two enzymes that convert p-Glu-His-Pro-Gly-OH into p-Glu-His-Pro-NH2 (thyrotropin-releasing hormone).

To study the possibility of glycine-directed amidation in rat brain, we synthesized the substrate p-Glu-His-Pro-Gly-OH. Adult and neonatal rat brain and adult rat pituitary were sonicated, frozen and thawed, and fractionated by gel permeation chromatography, and fractions from each tissue were assayed for enzymatic activity capable of converting this model substrate into thyrotropin-releasing hormone. We report the presence in rat brain and rat pituitary of two enzymes catalyzing conversion of p-Glu-His-Pro-Gly-OH into thyrotropin-releasing hormone. Based on the differing chemical and physical properties of these two enzymes and their differing affinities for a number of p-Glu-His-Pro-aa-OH analogs (in which aa = glycine, beta-alanine, gamma-butyric acid, and delta-aminovaleric acid), we conclude that there are two distinct enzymatic processes for the terminal amidation of peptides in brain and that COOH-terminal extensions other than glycine are capable of directing COOH-terminal amidation.

The dimethylheptyl derivative of (−)-Δ 8-tetrahydrocannabinol reduces the turnover rate of gamma-aminobutyric acid in the septum and nucleus accumbens

Accumulating evidence suggests that the cannabinoids exert their action to reduce the turnover rate of acetylcholine in the hippocampus by an action in the septum via inhibitory gamma-butyric acid (GABA) containing interneurons. In the studies presented here administration of the potent dimethylheptyl derivative of (−)-Δ-tetrahydrocannabinol, which has previously been shown to reduce the turnover rate of acetylcholine in the hippocampus, reduces the turnover rate of GABA in the septum. A simple model in which cannabinoids transsynaptically activate inhibitory GABAergic septal neurons impinging on cholinergic septal neurons does not explain the data. A more complex model suggesting that inhibitory GABAergic septal interneurons innervate other inhibitory GABAergic septal interneurons has been hypothesized.

Simultaneous reduction in the turnover rates of septal gamma-aminobutyric acid and hippocampal acetylcholine following administration of nabilone

Recent evidence suggests that the cannabinoids exert their action to reduce the turnover rate of acetylcholine in the hippocampus by an action in the septum via inhibitory gamma-butyric acid containing interneurons. In the studies presented here, administration of the synthetic, crystalline cannabinoid, nabilone, reduces the turnover rate of acetylcholine in the hippocampus and reduces the turnover rate of gamma-butyric acid in the septum. These events occur without altering the steady-state concentrations of either the precursors or the two putative neurotransmiters. The data can be explained by a number of working hypothesis. We have selected the hypothesis that a group of inhibitory gamma-butyric acid containing interneurons impinges on a second smaller group of inhibitory gamma-butyric containing interneurons which modulates the activity of cholinergic cell bodies located in the medial septum whose long axons project to the hippocampus.

PROTEUS VULGARIS URINARY TRACT INFECTIONS IN RATS; TREATMENT WITH NITROFURAN DERIVATIVES

Ascending urinary tract infections with stone formation have been produced experimentally in rats, using a modification of the method of Vermuelen & Goetz (1954a, b). A zinc disc infected with a culture of Proteus vulgaris was inserted into the bladder by suprapubic cystotomy under ether anaesthesia. The pH of the urine rises from 6.9 to 8 or 9 and calculi develop in the bladder within a few days of infection. The bladder and ureters become swollen, distended and inflamed, and renal abscesses develop. Death from renal failure generally occurs within 10 days of infection. Oral treatment with nitrofurantoin was commenced three days after infection and continued for one month. This arrested the initial rise in urine alkalinity and stone formation, and few, if any, macroscopic lesions were found at post-mortem examination. Of nine nitrofuran derivatives examined for activity against this infection several showed slight activity, but only one, N-(5-Nitrofurfurylidene)-gamma-butyric acid, was as active as nitrofurantoin when given at four times the dose, but it was also one-third as toxic. It is concluded that this technique is suitable for the examination of potential urinary antiseptics.