| 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) |
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| 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) |
| receptors, gaba | Cell-surface proteins that bind gaba with high affinity and trigger changes that influence the behaviour of cells. Gaba-a receptors control chloride channels formed by the receptor complex itself. They are blocked by bicuculline and usually have modulatory sites sensitive to benzodiazepines and barbiturates. Gaba-b receptors act through g-proteins on several effector systems, are insensitive to bicuculline, and have a high affinity for l-baclofen. (12 Dec 1998) |
| receptors, gaba-a | Cell surface proteins which bind gaba and control an integral membrane chloride channel. Gaba-a receptors are the most prevalent inhibitory neurotransmitter receptors in the brain. Several isoforms have been cloned, and they belong to a superfamily which includes nicotinic receptors, glycine receptors, and 5ht-3 receptors. Most gaba-a receptors have separate modulatory sites sensitive to benzodiazepines and to barbiturates. (12 Dec 1998) |
| receptors, gaba-b | Cell surface proteins which bind gaba and influence cells via interactions with g-proteins. Gaba-b receptors are pharmacologically characterised by their insensitivity to the blocker bicuculline and sensitivity to the agonist l-baclofen. They are found both presynaptically and postsynaptically, and act variously by inhibition of adenylate cyclase, activation of phospholipase a2, activation of potassium channels, and inactivation of voltage-activated calcium channels. (12 Dec 1998) |