| Ga | Symbol for gallium. (05 Mar 2000) |
|---|---|
| GABA | <biochemistry> An important amino acid which functions as the most prevalent inhibitory neurotransmitter in the central nervous system. Gamma aminobutyric acid works in partnership with a derivative of Vitamin B-6, pyridoxine, to cross from the axons to the dendrites through the synaptic cleft, in response to an electrical signal in the neuron and inhibits message transmission. This helps control the nerve cells from firing too fast, which would overload the system. The action of gamma aminobutyric acid decreases epileptic seizures and muscle spasms by inhibiting electrical signals in this manner. Studies have shown that the site of action in the brain of benzodiazepams, including Valium, is directly coupled to the brain receptor for gamma aminobutyric acid. Acronym: GABA (05 Jan 1998) |
| gaba agents | Substances used for their pharmacological actions on gabaergic systems. Gabaergic agents include agonists, antagonists, degradation or uptake inhibitors, depleters, precursors, and modulators of receptor function. (12 Dec 1998) |
| gaba agonists | Drugs that bind to and activate gaba receptors (receptors, gaba). (12 Dec 1998) |
| gaba antagonists | Drugs that bind to but do not activate gaba receptors, thereby blocking the actions of endogenous gaba or gaba agonists. (12 Dec 1998) |
| GABA dehydrogenase | <enzyme> From crude mitochondrial fraction of rat brain; reported first product is gamma-aminocrotonic acid; p-iodonitrotetrazolium violet can serve as acceptor of electrons Registry number: EC 1.- (26 Jun 1999) |
| gaba modulators | Substances that do not act as agonists or antagonists but do affect the gaba receptor-ionophore complex. Gaba-a receptors (receptors, gaba-a) appear to have at least three allosteric sites at which modulators act: a site at which benzodiazepines act by increasing the opening frequency of gaba-activated chloride channels; a site at which barbiturates act to prolong the duration of channel opening; and a site at which some steroids may act. General anaesthetics probably act at least partly by potentiating gabaergic responses, but they are not included here. (12 Dec 1998) |
| GABA pathway | The pathway that ultimately converts 4-aminobutyrate to succinate; succinate is then converted to alpha-ketoglutarate, via the tricarboxylic acid cycle, which is then acted upon by glutamate dehydrogenase; glutamate is then decarboxylated to reform 4-aminobutyrate; an important pathway for those cells which make this neuroactive molecule. Synonym: GABA pathway. (05 Mar 2000) |
| GABA permease | <chemical> From aspergillus nidulans; uga4 is from saccharomyces cerevisiae Synonym: gamma-amino-n-butyrate permease, 4-aminobutyric acid permease, uga4 protein, uga4 gene product (26 Jun 1999) |
| GABA receptor | <physiology> Ligand gated chloride ion channel forming receptor opened by gamma aminobutyric acid. Two distinct types: A and B. A receptor: One of a family of neurotransmitter receptors with fast intrinsic ion channels that includes the glycine receptor and the nicotinic acetylcholine receptor. Distinct from another major receptor family, the muscarininc acetylcholine receptor and rhodopsin, with no intrinsic ion channel. The A receptor is specifically blocked by bicuculline. It consists of two pairs of protein chains forming an A2B2 complex, the A chains bind benzodiazepine and the B chains bind GABA. The 4 subunits are thought to form a tight group with the chloride channel in the middle. There is considerable similarity between the amino acid sequences of the receptor subunits and those of the nicotinic acetylcholine receptor suggesting that both receptors are derived from some evolutionary ancestor. See: amino acid receptor superfamily. B receptor: Brain receptor (80 kD) for the inhibitory neurotransmitter gamma amino butyric acid. Differs from the A receptor both in agonist specificity (baclofen is a specific agonist) and its effects on cells. It modulates intracellular calcium levels through a Go mediated effect on N type calcium channels and also lowers intracellular cAMP levels by an effect on adenylyl cyclase, thereby reducing the secretion of catecholamines. (05 Jan 1998) |
| gabase | <chemical> Mixture of 4-aminobutyrate transaminase (EC 2.6.1.19) and succinate saemialdehyde dehydrogenase (nadp) (EC 1.2.1.16) from pseudomonas fluorescens; used in assay of gaba (26 Jun 1999) |
| gabbro | <geology> A name originally given by the Italians to a kind of serpentine, later to the rock called euphotide, and now generally used for a coarsely crystalline, igneous rock consisting of lamellar pyroxene (diallage) and labradorite, with sometimes chrysolite (olivine gabbro). Origin: It. Source: Websters Dictionary (01 Mar 1998) |
| gabel | A rent, service, tribute, custom, tax, impost, or duty; an excise. "He enables St. Peter to pay his gabel by the ministry of a fish." (Jer. Taylor) Origin: F. Gabelle, LL. Gabella, gabulum, gablum; of uncertain origin. Cf.Gavel tribute. Source: Websters Dictionary (01 Mar 1998) |
| gabexate | <chemical> 4-((6-((aminoiminomethyl)amino)-1-oxohexyl)oxy)benzoic acid ethyl ester. A serine proteinase inhibitor used therapeutically in the treatment of pancreatitis, disseminated intravascular coagulation (dic), and as a regional anticoagulant for haemodialysis. The drug inhibits the hydrolytic effects of thrombin, plasmin, and kallikrein, but not of chymotrypsin and aprotinin. Pharmacological action: anticoagulant, serine proteinase inhibitors. Chemical name: Benzoic acid, 4-((6-((aminoiminomethyl)amino)-1-oxohexyl)oxy)-, ethyl ester (12 Dec 1998) |
| gabion | 1. A hollow cylinder of wickerwork, like a basket without a bottom. Gabions are made of various sizes, and filled with earth in building fieldworks to shelter men from an enemy's fire. 2. <physics> An openwork frame, as of poles, filled with stones and sunk, to assist in forming a bar dyke, etc, as in harbor improvement. Origin: F, from It. Gabbione a large cage, gabion, from gabbia cage, L. Cavea. See Cage. Source: Websters Dictionary (01 Mar 1998) |