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Results for “AMINOBUTYRIC ACID”

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At least 127 records · Page 7Linked to original sources
PubMed1990

4-Amino-3-alkylbutanoic acids as substrates for gamma-aminobutyric acid aminotransferase.

A variety of alkyl-substituted 4-aminobutanoic acid derivatives, including a homologous series of 3-alkyl-4-aminobutanoic acid analogues, 4-methyl isomer analogues, the 3,3-dimethyl analogue, and (E)-4-amino-3-methyl-2-butenoic acid, were synthesized and tested as alternate substrates for purified gamma-aminobutyric acid aminotransferase from pig brain. All of the compounds were substrates, but their activities diminished as the size and bulk of the 3-alkyl substituent increased. Several differences were observed between the alkyl-substituted analogues and the corresponding aryl-substituted compounds previously reported (Silverman, R. B., Invergo, B. J., and Levy, M. A. (1987) J. Biol. Chem. 262, 3192-3195). These findings will be important in future designs of inhibitors of gamma-aminobutyric acid aminotransferase.

4-Aminobutyrate Transaminase↗
PubMed1992

Antiulcer and gastric secretory activity of N-phthaloyl gamma-aminobutyric acid.

N-Phthaloyl gamma-aminobutyric acid, a new gamma-aminobutyric acid derivative synthesized in this laboratory, has been found to possess anticonvulsant, antinociceptive and antistress activities. Effects of this derivative on gastric lesions induced by aspirin and ethanol were studied in rats. N-Phthaloyl gamma-aminobutyric acid significantly inhibited both aspirin and alcohol ulceration. The ED50 in each case being 76.34 and 43.65 mg/kg i.p. respectively. The volume of gastric acid secretion was diminished but gastric mucus secretion was significantly enhanced. The antiulcer effect was blocked by bicuculline and 3-mercaptopropionic acid. We conclude that (a) N-phthaloyl gamma-aminobutyric acid possesses antiulcer activity (b) the new derivative is probably a non-specific gamma-aminobutyric acid receptor agonist (c) the observed activity may be due to a mucoprotective action.

3-Mercaptopropionic Acid↗
PubMed1980

Concomitant increases in serum growth hormone and hypothalamic somatostatin in rats after injection of gamma-aminobutyric acid, aminooxyacetic acid, or gamma-hydroxybutyric acid.

gamma-Aminobutyric acid (GABA; 50 or 500 microgram/10 microliter) was injected into the right lateral ventricle of urethane- or pentobarbital-anesthetized male rats. The animals were decapitated 15 min after injection. Serum GH and hypothalamic somatostatin (SRIF) concentration were measured by specific RIAs. Intraventricular GABA caused a dose-related increase in GH and SRIF. In another study, aminooxyacetic acid (5 or 20 mg) was injected ip into urethane-anesthetized rats. Aminooxyacetic acid at 20 mg produced a significant increase in both serum GH and hypothalamic SRIF. Furthermore, 12.5 mg gamma-hydroxybutyric acid (GHB) injected ip into urethane- or pentobarbital-anesthetized rats elicited a significant increase in both serum GH and hypothalamic SRIF. Pretreatment with 20 mg L-dopa produced decreases in the GHB-induced serum GH increase and in hypothalamic SRIF in pentobarbital-anesthetized rats. These results show that GABA and GHB stimulated GH secretion, which was accompanied by increased hypothalamic SRIF. Thus, the GH release induced by GABA or GHB may be partly involved in inhibiting the release of hypothalamic SRIF. As the GHB-induced GH release was inhibited by L-dopa, the stimulatory effect of GHB on GH secretion might be mediated by inhibition of the dopaminergic mechanism.

Acetates↗
PubMed1994

Decrease of glutamate decarboxylase activity after in vivo cortical infusion of gamma-aminobutyric acid.

gamma-Aminobutyric acid (GABA) levels and the activity of glutamate decarboxylase were measured in homogenates of rat brain cortical tissue, at different times after chronic intracortical infusion of GABA in vivo during 2, 6 or 24 h. Cortical electrical activity was also recorded. As previously described, about 1 h after cessation of the infusion epileptic discharges were observed (GABA-withdrawal syndrome), which lasted for several days. At zero time after cessation of the infusion, before the appearance of seizures, GABA levels were increased 3-6-fold and glutamate decarboxylase activity was decreased 27-48% in the infused cortex, as compared to the contralateral cortex or to tissue from control intact rats. During epileptic discharges GABA levels gradually returned to normal values. In contrast, glutamate decarboxylase activity remained decreased during seizures and returned to normal only after recovery from the GABA-withdrawal syndrome. These results suggest that the persistent decrease in the activity of the decarboxylase is due probably to a lowered amount of the enzymatic protein, occurring as a consequence of a temporarily elevated intracellular GABA concentration. The decreased rate of GABA synthesis might be involved in the pathophysiology of the GABA-withdrawal syndrome.

Amino Acids↗
PubMed1996

Recognition of chiral conformations of the achiral neurotransmitter, gamma-aminobutyric acid.

gamma-Aminobutyric acid (GABA), a flexible achiral neurotransmitter, acts at different subclasses of receptors and participates in transport processes. Conformationally restricted GABA analogues exert selective biological effects. Besides fulfilling conformational recognition by different binding sites of receptors, and proteins involved in inactivation mechanisms, the flexible neurotransmitter may also endure the variation of conformation connected with receptor function. In addition to different conformations distinguished by torsion angles of the GABA backbone, distinct molecular torsions are suggested for the GABAA receptor subclass and for the transport process.

Ligands↗
PubMed1981

Reductions in blood pressure, heart rate and renal sympathetic nervous discharge after imidazole-4-acetic acid: mediation through central gamma-aminobutyric acid (GABA) receptor stimulation.

Intracerebroventricular administration of imidazole-4-acetic acid (IAA) (0.3--10 microgram/kg) significantly reduced mean arterial pressure, heart rate and renal sympathetic nerve discharge in chloralose-anesthetized cats. In contrast, i.v. administration of IAA did not lower arterial pressure or heart rate. This would suggest that the hypotensive and bradycardic effects of IAA were centrally mediated. The cardiovascular effects of IAA were attenuated by the central administration of bicuculline methiodide (15 microgram/kg), a gamma-aminobutyric acid receptor antagonist. Reflex bradycardia evoked during the pressor response to norepinephrine (0.03--1.0 microgram/kg i.v.) was reversed to tachycardia after only the central administration of IAA. The vasoconstrictor response evoked during a 20-sec period of bilateral occlusion of carotid arteries was not altered by IAA. These results suggest that the cardiovascular effects of IAA are mediated through the activation of central gamma-aminobutyric acid receptors, to inhibit sympathetic vasomotor outflow.

Animals↗
PubMed1986

Potentiation of salivary fluid secretion in ixodid ticks: a new receptor system for gamma-aminobutyric acid.

gamma-Aminobutyric acid (GABA), having minimal intrinsic activity, potentiates dopamine-induced fluid secretion in salivary glands of female ixodid ticks. Because the effect of GABA was similar to that of spiperone, we tested whether these two drugs act at a common recognition site. Potentiation was not augmented when salivary glands were exposed to supramaximal concentrations of spiperone (1 microM) plus GABA (100 microM). (+/-)-Sulpiride (100 microM), a spiperone antagonist in this system, also blocked GABA-induced potentiation. Picrotoxin (100 microM) and (-)-bicuculline (100 microM), two GABA antagonists, blocked GABA-induced and spiperone-induced potentiation. Inhibition of GABA by picrotoxin and (-)-bicuculline was noncompetitive. Muscimol (an agonist at GABAA receptors) also potentiated dopamine-induced secretion. Baclofen (an agonist at GABAB receptors) did not elicit potentiation. We suggest that GABA may function as a neuromodulator for dopamine-induced fluid secretion in tick salivary glands.

Animals↗
PubMed1986

Effects of arachidonic acid on glutamate and gamma-aminobutyric acid uptake in primary cultures of rat cerebral cortical astrocytes and neurons.

The effects of arachidonic acid on glutamate and gamma-aminobutyric acid (GABA) uptake were studied in primary cultures of astrocytes and neurons prepared from rat cerebral cortex. The uptake rates of glutamate and GABA in astrocytic cultures were 10.4 nmol/mg protein/min and 0.125 nmol/mg protein/min, respectively. The uptake rates of glutamate and GABA in neuronal cultures were 3.37 nmol/mg protein/min and 1.53 nmol/mg protein/min. Arachidonic acid inhibited glutamate uptake in both astrocytes and neurons. The inhibitory effect was observed within 10 min of incubation with arachidonic acid and reached approximately 80% within 120 min in both types of culture. The arachidonic acid effect was not only time-dependent, but also dose-related. Arachidonic acid, at concentrations of 0.015 and 0.03 mumol/mg protein, significantly inhibited glutamate uptake in neurons, whereas 20 times higher concentrations were required for astrocytes. The effects of arachidonic acid were not as deleterious on GABA uptake as on glutamate uptake in both astrocytes and neurons. In astrocytes, GABA uptake was not affected by any of the doses of arachidonic acid studied (0.015-0.6 mumol/mg protein). In neuronal cultures, GABA uptake was inhibited, but not to the same degree observed with glutamate uptake. Lower doses of arachidonic acid (0.03 and 0.015 mumol/mg protein) did not affect neuronal GABA uptake. Other polyunsaturated fatty acids, such as docosahexaenoic acid, affected amino acid uptake in a manner similar to arachidonic acid in both astrocytes and neurons. However, saturated fatty acids, such as palmitic acid, exerted no such effect. The significance of the arachidonic acid-induced inhibition of neurotransmitter uptake in cultured brain cells in various pathological states is discussed.

Animals↗