Glutamate receptors are implicated in the genesis of opioid tolerance and dependence. Factors governing release of amino acids in systems chronically exposed to opiates, however, remain undefined. Using rats, each prepared with a spinal loop dialysis catheter and with a chronic lumbar intrathecal infusion catheter connected to a subcutaneous minipump, the release of amino acids before and durin...

BACKGROUND Clonidine has been shown to be a potent neuroprotectant by acting at α(2) receptors on glutamatergic neurons to inhibit the release of glutamate. The aim of this study is to investigate the effects of clonidine on the activity of EAAT3 that can regulate extracellular glutamate. METHODS EAAT3 was expressed in the Xenopus oocytes. Using a two-electrode voltage clamp, membrane current...

Membrane-bound glutamate carboxypeptidase II (GCPII) is a zinc metalloenzyme that catalyzes the hydrolysis of the neurotransmitter N-acetyl-L-aspartyl-L-glutamate (NAAG) to N-acetyl-L-aspartate and L-glutamate (which is itself a neurotransmitter). Potent and selective GCPII inhibitors have been shown to decrease brain glutamate and provide neuroprotection in preclinical models of stroke, amyotr...

Recent evidence indicates that L-glutamate is taken up into synaptic vesicles in an ATP-dependent manner, supporting the notion that synaptic vesicles may be involved in glutamate synaptic transmission. In this study, we further characterized the ATP-dependent vesicular uptake of glutamate. Evidence is provided that a Mg-ATPase, not Ca-ATPase, is responsible for the ATP hydrolysis coupled to th...

BACKGROUND AND PURPOSE The objective of this study was to assess the effect of therapeutic moderate hypothermia on excitatory amino acids and metabolism by applying cerebral microdialysis in patients suffering from space-occupying middle cerebral artery infarction. METHODS This was an open, prospective, observational study of 12 patients undergoing moderate hypothermia (33 degrees C) as rescu...

Monosodium glutamate (MSG) is believed to elicit a unique taste perception known as umami. We have used conditioned taste aversion assays in rats to compare taste responses elicited by the glutamate receptor agonists MSG, L-aspartic acid (L-Asp), and N-methyl-D-aspartate (NMDA), and to determine if these compounds share a common taste quality. This information could shed new light upon the rece...

Intact avian liver mitochondria were shown to synthesize glutamine from glutamate in the absence of exogenous ATP and ammonia. With L-[U-14C]glutamate as the substrate, there was an approximate 1:1 stoichiometry between glutamate deaminated (as measured by the release of 14CO2 due to alpha-keto-[14C]glutarate oxidation) and glutamate amidated. With L-[15N]glutamate as the substrate, the isolate...

The L-glutamine- and N-acetyl-L-glutamate-dependent carbamoyl phosphate synthetase III present in liver of spiny dogfish (Squalus acanthias) has been purified to a high state of purity. The purified enzyme has a Mr congruent to 160,000 and is subject to self-association which is facilitated by the presence of MgATP, L-glutamine, and N-acetyl-L-glutamate. The enzyme exhibits hysteretic propertie...

Glutamate dehydrogenase (L-glutamate-NAD(P) oxidoreductase EC 1.4.1.3) from bovine liver catalyzes the reversible oxidative deamination of various monocarboxylic amino acids, as well as of n-glutamate (1, 2). Several years ago, we reported that estrogenic steroids both inhibited the oxidation of L-glutamate (3) and stimulated the oxidation of L-alanine (4). Conversely, adenosine diphosphate was...