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At least 1,225 records · Page 68Linked to original sources
PubMed1985

Gabapentin decreases monoamine release without affecting acetylcholine release in the brain.

Superfused rat brain cortex slices preincubated with 3H-noradrenaline or 3H-serotonin and superfused rabbit caudate nucleus slices preincubated with 3H-choline were used to examine the effects of gabapentin (an amino acid chemically related to gamma-aminobutyric acid, GABA) on the electrically evoked 3H overflow. Gabapentin inhibited the electrically (3 Hz) evoked 3H overflow from slices preincubated with the 3H-monoamines in a concentration-dependent manner (at 1 mmol/l by 20-30%), but did not affect the evoked overflow from slices preincubated with 3H-choline. The following drugs did not modify the inhibitory effects of gabapentin: bicuculline, RS-baclofen, GABA, phentolamine, metitepin, cocaine, and the inhibitor of serotonin uptake, 6-nitroquipazine. Gabapentin did not modify the inhibitory effect of GABA on the evoked 3H overflow from slices preincubated with 3H-serotonin. In slices preincubated with 3H-noradrenaline the inhibitory effect of gabapentin was still observed when the stimulation frequency was 10 instead of 3 Hz. In conclusion, gabapentin mimics GABAB receptor activation, but it appears to act by a GABA receptor-independent, as yet unidentified mechanism.

Acetates↗
PubMed1978

Dehydroquinate synthase in Bacillus subtilis. An enzyme associated with chorismate synthase and flavin reductase.

Dehydroquinate synthase, the enzyme which catalyzes the conversion of 3-deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP) to 5-dehydroquinate, has been purified from Bacillus subtilis in association with chorismate synthase and NADPH-dependent flavin reductase. The enzyme was only active when associated with chorismate synthase, whereas the flavin reductase could be separated from the complex with retention of dehydroquinate synthase activity. The enzyme requires NAD and either Co2+ or Mn2+ for maximal activity. The activity was completely inhibited by EDTA. The Km of the enzyme for DAHP, NAD, and Co2+ were estimated to be 1.3 X 10(-4), 5.5 X 10(-5), and 5.5 X 10(-5) M, respectively. Enzyme activity was completely inhibited by NADH and the inhibition was not reversed by the addition of NAD, NADPH and NADP were not inhibitory. The enzyme was unstable to heat and lost all activity at 55 degrees C. A protein fraction which did not adsorb to phosphocellulose was found to inhibit the enzyme.

Bacillus subtilis↗
PubMed1991

GABA synthesis in brain slices is dependent on glutamine produced in astrocytes.

The rate of gamma-aminobutyric acid (GABA) synthesis in rat-brain slices was determined by inhibiting GABA transaminase with 20-microM gabaculine and measuring the increase of GABA. Added 500-microM glutamine increased the rate of GABA synthesis by 50%, indicating that glutamate decarboxylase is not saturated in brain slices. The stimulation of GABA synthesis with added glutamine in brain slices was much less than that reported for synaptosomes. The lower stimulation in slices was attributable to astrocytic glutamine production, as the rate of GABA synthesis decreased by 44% when glutamine production was inhibited with methionine sulfoximine. Added glutamine restored the rate to the maximal value observed in brain slices. The rate of GABA synthesis was decreased by 65% in slices pretreated with an inhibitor of glutaminase, and added glutamine did not reverse this effect. These results suggest that glutamine produced by astrocytes is a quantitatively important precursor of GABA synthesis in cortical slices.

4-Aminobutyrate Transaminase↗
PubMed2004

GABAB receptors do not mediate the inhibitory actions of gabapentin on the spinal reflex in rats.

The clinical effectiveness of gabapentin for the treatment of epilepsy, spasticity, and neuropathic pain has been established. The mechanisms responsible for those actions, however, are still not clearly understood. We have recently demonstrated that gabapentin reduces the spinal reflex in rats via mechanisms that do not involve gamma-aminobutyric acid (GABA)A receptors. In the study, we attempted to explore the involvement of GABAB receptors in gabapentin-induced inhibition of the spinal reflexes in spinalized rats. Stimulation of the dorsal root at L5 elicited the segmental mono-(MSR) and polysynaptic reflex (PSR) in the ipsilateral ventral root. The microinjection of gabapentin (1.5 and 5 nmol) into the ventral horn reduced both MSR and PSR, whereas the injection into the dorsal horn only inhibited the PSR, indicating that systemic gabapentin inhibits the MSR at the ventral horn and it inhibits the PSR at both the ventral and dorsal horns. The GABAB-receptor antagonist CGP35348 (0.5 nmol) injected into the ventral horn antagonized the inhibition of the spinal reflexes by the GABAB-receptor agonist baclofen (i.v.) but not by gabapentin (i.v.). Thus, GABAB receptors do not appear to contribute to the gabapentin-induced inhibition of the spinal reflex.

Amines↗
PubMed1999

3-substituted GABA analogs with central nervous system activity: a review.

Gabapentin and Pregabalin are both 3-alkylated gamma-amino butyric acid (GABA) analogs. Gabapentin was designed as a lipophilic GABA analog and was first synthesized as a potential anticonvulsant and was launched in 1994 as add-on therapy for the treatment of epilepsy. In this review the discovery and development of gabapentin as an anticonvulsant are discussed. During human trials and while in clinical use, it became apparent that gabapentin induced some other potentially useful therapeutic effects in chronic pain states and behavioral disorders. A review of animal and clinical data relating to these other potential therapeutic utilities is presented. Pregabalin was identified after an investigation into other 3-substituted GABA analogs. It has since been shown to have a similar pharmacological profile to gabapentin with greater potency in preclinical models of pain and epilepsy. Studies of the mechanism(s) of action of these compounds are discussed. Work towards identifying new analogs of both gabapentin and pregabalin is also reviewed.

Acetates↗
PubMed1981

The effects on extraction wound healing of a new drug combination introduced for use in the prevention of post-extraction complications. A preliminary report.

Fifteen extraction sockets packed with a new drug combination which includes a local anaesthetic (cincain chloride), a local antiseptic (tri-iodomethane) and two drugs with a potent antifibrinolytic activity (tranexamic acid and propyl-hydroxy-benzoic acid) in an absorbable gelatin sponge (Gelfoam) as a vehicle, were histologically assessed with special reference to the parameters related to wound healing. As a control, the same number of sockets were allowed to heal spontaneously and similarly assessed. Healing of the extraction wounds seemed to follow the normal sequence in both series, and no histological signs suggestive of a delay in the healing process could be found in any of the sockets studied. Also the mast cell count previously considered to be of importance in the connective tissue repair was found to be unaffected by the test substance. These results, together with the previously presented data on the clinical efficacy of the drug combination studied, suggest that a larger clinical study should be carried out to assess its value as a preventive measure against the development of the post-extraction symptoms, including dry socket.

Adolescent↗
PubMed2001

Memory improving actions of gabapentin in mice: possible involvement of central muscarinic cholinergic mechanism.

Male CF-1 mice were tested 48 h after training on a one trial step-through inhibitory avoidance task. Immediately post-training, intraperitoneal (i.p.) injections of the antiepileptic gabapentin (1-(aminomethyl) cyclohexaneacetic acid) (GBP, 10 mg/kg) enhanced retention performance. The effect was prevented by atropine, a central muscarinic cholinergic receptor antagonist (0.5 mg/kg, i.p.) administered after training but 10 min prior to GBP treatment. In contrast, neither methylatropine (0.5 mg/kg, i.p.), a peripherally acting muscarinic receptor blocker, nor mecamylamine (5 mg/kg, i.p.) or hexamethonium (5 mg/kg, i.p.), two cholinergic nicotinic receptor antagonists, prevented the effects of post-training GBP on retention performance. Low subeffective doses of the central acting anticholinesterase physostigmine (35 mg/kg, i.p.) administered immediately after training, and GBP (5 mg/kg, i.p.), given 10 min after training, significantly enhanced retention performance. The effects of GBP (5 mg/kg, i.p.) were not influenced by the peripherally acting anticholinesterase neostigmine (150 mg/kg, i.p.). Considered together, these findings suggest a disinhibitory action of GBP on the activity of central muscarinic cholinergic mechanisms that are involved in memory consolidation.

Acetates↗
PubMed1976

The cause of G2-arrest in Chinese hamster ovary cells treated with anticancer drugs.

The nature of G2-arrest was studied in Chinese hamster ovary cells after exposure to 4'-demethyl-epipodophyllotoxin 9-)4,6-0-2-thenylidene-beta-D-glycopyranoside (VM26), 1,3-bis(2-chloroethyl)-1-nitrosourea, 1,3-cis(2-chloroethyl)-1-nitrosourea, cis-4[[[(2-chloroethyl)-nitrosoamino] carbonyl] amino]- cyclohexane carboxylic acid, or neocarzinostatin. To determine whether this G2-arrest was due to a metabolic block or to damage to the genetic material, we employed the phenomenon of premature chromosome condensation to visualize the chromosomes of the G2-blocked cells by fusing them with mitotic cells. The prematurely condensed chromosomes (PCC) of the treated cells were scored for their position in the cell cycle and the extent of chromosomal damage in the G2-PCC. The data revealed a significant enrichment of the G2-fraction in all the treatments. Most of the G2- PCC from the treated cells were extensively damaged, showing 10 or more breaks and exchanges per cell. These studies clearly indicated that the treated cells accumulated in G2-phase because of their failure to progress into mitosis as a direct or indirect result of the extensive damage to the chromosomes.

Animals↗
PubMed1981

A new combination of drugs intended to be used as a preventive measure for the postextraction complications. A preliminary report.

Fifteen extraction sockets packed with a new drug combination, including a local anesthetic (cincain chloride), a local antiseptic (tri-iodomethane) and two drugs with a potent antifibrinolytic activity (tranexamic acid and propyl-hydroxybenzoic acid) in Gelfoam as a vehicle, were assessed clinically with special reference to the development of the postextraction symptoms, dry socket included. As a control series, 15 extraction sockets allowed to undergo a spontaneous healing were similarly evaluated. All the sockets in both series were found to heal according to the normal sequence. There were, however, statistically highly significant differences between the two series with regard to the clotting time, postextraction pain and the need for adjunct analgesics, in favor of the sockets packed with the compound in test. The observed beneficial effects of the test compound are discussed in the light of the recently elucidated etiologic and pathogenetic mechanisms leading to the development of dry socket, and a conclusion is drawn that the present results, although preliminary due to the limited number of patients, advocate further evaluation of the new drug combination and its applicability in the prevention of the troublesome postextraction complications, including dry socket.

Adolescent↗
PubMed1997

Psychomotor agitation following gabapentin use in brain injury.

Gabapentin, an anticonvulsant structurally related to gamma-aminobutyric acid (GABA) was recently reported to be effective in pain associated with reflex sympathetic dystrophy (RSD) and in pain associated with neuropathy. Yet, to our knowledge, the use of gabapentin for neuropathic pain in the presence of cognitive impairment has not been reported. In this report, we describe two patients (one with a traumatic brain injury, one with a putative acquired brain injury) who presented to a neurorehabilitation unit complaining of pain that was diagnosed as neurologically mediated. Within one week of receiving a daily 900 mg dose of gabapentin, both patients complained of heightened anxiety and restlessness. Correspondingly, each reported a diminution of psychological symptoms within 48 hours of gabapentin cessation. These two cases suggest that gabapentin may cause agitation in cognitive impaired patients. Physicians treating brain-injured patients and prescribing gabapentin for neuropathic pain may wish to closely monitor patients for similar signs of restlessness or anxiety.

Acetates↗
PubMed1990

Gabapentin in partial epilepsy. UK Gabapentin Study Group.

Gabapentin is an analogue of gamma aminobutyric acid (GABA) which has anticonvulsant properties in animals. In a multicentre, double-blind, placebo-controlled, parallel-group study of 1200 mg/day gabapentin as additional therapy in 127 patients with drug-resistant partial epilepsy, 25% of patients who received gabapentin had the number of partial seizures at least halved, compared with 9.8% of patients given placebo. The median reduction in partial seizure frequency during 12 weeks' treatment was 29.2% with gabapentin compared with 12.5% with placebo. The mean adjusted response ratio for gabapentin (-0.192) was significantly better than the ratio of -0.060 for placebo by analysis of variance. 62% of patients who received gabapentin reported mostly mild or moderate adverse effects compared with 41% on placebo; no interactions were observed between gabapentin and other standard anticonvulsants. Gabapentin is an effective additional treatment for patients with partial epilepsy refractory to standard therapy, is fairly well tolerated, and appears to have a favourable efficacy-to-toxicity ratio.

Acetates↗
PubMed2004

Determination of gabapentin in human plasma by capillary electrophoresis with laser-induced fluorescence detection and acetonitrile stacking technique.

A sensitive analytical method for gabapentin [1-(aminomethyl) cyclohexaneacetic acid] (GBP) in human plasma based on capillary electrophoretic separation and laser-induced fluorescence (LIF) detection has been developed. 6-Carboxyfluorescein succinimidyl ester (CFSE) was used for precolumn derivatization of the non-fluorescent drug in plasma. Optimal separation and detection were obtained with an electrophoretic buffer of 50mM sodium borate (pH 9.5) and an air-cooled argon-ion laser (excitation at 488 nm, emission at 520 nm). A calibration curve ranging from 0.3 to 150 microM was shown to be linear. The concentration limit of detection (LOD) in plasma was 60 nM. We also demonstrate how the detection limit can be enhanced by using acetonitrile stacking technique. With stacking, the limit of detection for gabapentin in plasma was 4.8 nM. A calibration curve ranging from 0.03 to 15 microM was shown to be linear. Both the within-day and day-to-day reproducibility and accuracy were </=10.8 and 6.0%, respectively.

Acetates↗
PubMed2004

Endogenous GABA does not mediate the inhibitory effects of gabapentin on spinal reflexes in rats.

The novel antiepileptic drug gabapentin was designed as a structural analog of gamma-aminobutyric acid (GABA). However, its mechanism of action remains unclear. In the present study, we investigated the effect of gabapentin on spinal reflexes in anesthetized rats. The mono- and polysynaptic reflex potentials were recorded from the ipsilateral L5 ventral root after stimulation of the L5 dorsal root. The dorsal root reflex potential, an index of presynaptic inhibition, was recorded from the ipsilateral L4 dorsal root. In non-spinalized (intact) and spinalized rats, intravenously administered gabapentin reduced the mono- and polysynaptic reflex potentials in a dose-dependent manner. These inhibitory effects of gabapentin were not suppressed by the GABA(A) antagonist picrotoxin. Moreover, gabapentin also decreased spinal reflexes in spinalized rats depleted of spinal GABA with semicarbazide, an inhibitor of the GABA-synthesizing enzyme. The dorsal root reflex potentials were not affected by gabapentin. These results suggest that endogenous GABA does not mediate the inhibitory effects of gabapentin on spinal reflexes.

Acetates↗
PubMed1973

tyrR, a regulatory gene of tyrosine biosynthesis in Salmonella typhimurium.

4-Fluorophenylalanine-resistant mutants of Salmonella typhimurium were isolated in which tyrosine pathway enzymes were not repressed by l-tyrosine. The mutants produced elevated levels of 3-deoxy-d-arabinoheptulosonic acid 7-phosphate (DAHP) synthetase (tyr) and chorismate mutase T-prephenate dehydrogenase, and these enzymes as well as transaminase A were not repressed by high concentrations of tyrosine. Genetic analysis revealed that a mutation in a gene designated tyrR was responsible for the constitutivity of the tyrosine pathway enzymes in strains SG1, SG7, and SG9, and that tyrR was linked to pyrF. In strain SG1 a mutation had also occurred in aroF, the structural gene for DAHP synthetase (tyr), resulting in loss of sensitivity of this enzyme to end-product inhibition. There appeared to be no relationship between loss of feedback inhibition and loss of end-product repression, since derivative strains of SG1 that carried only the tyrR mutation behaved like the singly mutated tyrR strains, SG7 and SG9, in showing high constitutive levels of tyrosine-specific enzymes that were not repressed by tyrosine.

Aldehyde-Lyases↗
PubMed1978

Metabolism of cyclohexane carboxylic acid by Alcaligenes strain W1.

Thirty-three microorganisms capable of growth with cyclohexane carboxylate as the sole source of carbon were isolated from mud, water, and soil samples from the Aberystwyth area. Preliminary screening and whole-cell oxidation studies suggested that, with one exception, all of the strains metabolized the growth substrate by beta-oxidation of the coenzyme A ester. This single distinctive strain, able to oxidize rapidly trans-4-hydroxycyclohexane carboxylate, 4-ketocyclohexane carboxylate, p-hydroxybenzoate, and protocatechuate when grown with cyclohexane carboxylate, was classified as a strain of Alcaligenes and given the number W1. Enzymes capable of converting cyclohexane carboxylate to p-hydroxybenzoate were induced by growth with the alicyclic acid and included the first unambiguous specimen of a cyclohexane carboxylate hydroxylase. Because it is a very fragile protein, attempts to stabilize the cyclohexane carboxylate hydroxylase so that a purification procedure could be developed have consistently failed. In limited studies with crude cell extracts, we found that hydroxylation occurred at the 4 position, probably yielding the trans isomer of 4-hydroxycyclohexane carboxylate. Simultaneous measurement of oxygen consumption and reduced nicotinamide adenine dinucleotide oxidation, coupled with an assessment of reactant stoichiometry, showed the enzyme to be a mixed-function oxygenase. Mass spectral analysis enabled the conversion of cyclohexane carboxylate to p-hydroxybenzoate by cell extracts to be established unequivocally, and all of our data were consistent with the pathway: cyclohexane carboxylate --> trans-4-hydroxycyclohexane carboxylate --> 4-ketocyclohexane carboxylate --> p-hydroxybenzoate. The further metabolism of p-hydroxybenzoate proceeded by meta fission and by the oxidative branch of the 2-hydroxy-4-carboxymuconic semialde-hyde-cleaving pathway.

Alcaligenes↗
PubMed2000

Inhibition of K(+)-evoked glutamate release from rat neocortical and hippocampal slices by gabapentin.

Gabapentin (Neurontin((R))) has preclinical and clinical efficacy as an anticonvulsant, antihyperalgesic, anxiolytic, and neuroprotective drug. Since L-glutamic acid (GLU) is involved in various CNS (central nervous system) disorders, gabapentin may attenuate the release of this neurotransmitter possibly by interacting with the auxiliary alpha(2)delta subunit of voltage-sensitive calcium channels (VSCC). The effects of gabapentin, pregabalin (S-(+)-3-isobutylgaba) and its enantiomer R-(-)-3-isobutylgaba, and N- and P/Q-type VSCC-targeting peptide ligands (omega-conotoxin MVIIA, omega-conotoxin MVIIC, omega-agatoxin TK) were assessed in vitro on K(+)-evoked (endogenous) GLU release from rat neocortical and hippocampal slices. Gabapentin and pregabalin decreased GLU release by 11-26% with R-(-)-3-isobutylgaba being less effective than pregabalin. The reference N- and P/Q-type VSCC-targeting ligands reduced GLU release by 19-55% to implicate these VSCC in this Ca(2+)-dependent process. The inhibitory effect of gabapentin and related compounds on GLU release may reflect a subtle modulation of VSCC function which normalizes pathological changes in neurotransmitter release.

Acetates↗
PubMed2006

Inhibitory effect of gabapentin on N-methyl-D-aspartate receptors expressed in Xenopus oocytes.

BACKGROUND: Gabapentin (GBP) is a prescription drug used for the treatment of neuropathic and post-operative pain. However, the mechanism by which it exerts its analgesic action is not well understood. Because intrathecal administration of GBP has been shown to exert antinociceptive effects in animal studies, we hypothesized that the spinal cord may be a plausible action site. METHODS: We examined the effects of GBP on neurotransmitter-gated ion channels and G protein-coupled inwardly rectifying potassium (GIRK) channels distributed in the spinal cord and involved in pain modulation. Recombinant human NR1/NR2A N-methyl-D-aspartate (NMDA), alpha(1)beta(2)gamma(2S)gamma-aminobutyric acid type A (GABA(A)) or alpha(1) glycine receptors, or GIRK1/GIRK2 channels were expressed in Xenopus laevis oocytes and the effects of GBP (0.1-1000 microM) on them were assessed using a two-electrode, voltage-clamp system. RESULTS: GABA(A) and glycine receptors and GIRK channels were not affected by GBP, even at the highest concentrations. Conversely, NMDA receptors were inhibited by GBP in a concentration-dependent manner, with significant inhibition observed at 10 microM. At 30 microM, GBP inhibited the glutamate-concentration response curve without changing the half-maximal effective concentration or the Hill coefficient, indicating a non-competitive inhibition. Glycine decreased the inhibitory effect in a concentration-dependent manner. CONCLUSIONS: These findings suggest that the inhibitory effect of GBP on NMDA receptors may play an important role in the antinociceptive property of GBP; however, it does not appear that GABA(A) and glycine receptors or GIRK channels contribute to the pharmacological properties of GBP.

Amines↗
PubMed2003

Pregabalin and gabapentin reduce release of substance P and CGRP from rat spinal tissues only after inflammation or activation of protein kinase C.

Gabapentin and pregabalin are amino acid derivatives of gamma-amino butyric acid that have anticonvulsant, analgesic, and anxiolytic-like properties in animal models. The mechanisms of these effects, however, are not well understood. To ascertain whether these drugs have effects on sensory neurons, we studied their actions on capsaicin-evoked release of the sensory neuropeptides, substance P and calcitonin gene-related peptide from rat spinal cord slices in vitro. Although release of immunoreactive peptides from non-inflamed animals was not altered by either drug, prior in vivo treatment by intraplantar injection of complete Freund's adjuvant enhanced release from spinal tissues in vitro, which was attenuated by gabapentin and pregabalin. These drugs also reduced release of immunoreactive neuropeptides in spinal tissues pretreated in vitro with the protein kinase C activator, phorbol 12,13-dibutyrate. Our results suggest that gabapentin and pregabalin modulate the release of sensory neuropeptides, but only under conditions corresponding to significant inflammation-induced sensitization of the spinal cord.

Acetates↗