GABA--an inhibitory neurotransmitter that is involved in cardiovascular control.
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Biomedical subjects
Publications and source records attributed to F V DeFeudis.
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Tetracycline injection (45 mg/kg, i.v.) produced increases in plasma urea and creatinine levels in rats. The greatest increases occurred after 24 hr for urea and after 6 hr for creatinine, the latter effect persisted for at least 30 hr. The actions of six diuretics (acetazolamide, bumetanide, chlorothiazide, chlorthalidone, triamterene and indapamide) given orally either as pretreatment (1 hr before tetracycline injection) or post-treatment (4 hr after tetracycline injection) were examined. When given as pretreatments, all six diuretics reduced the hyperuraemia, and generally the hypercreatininaemia, that existed 24 hr after tetracycline injection. In contrast, when given as post-treatments, only bumetanide reduced the increase in urea and creatinine levels. It is postulated that this protective action of diuretics could occur by their displacement of tetracycline molecules from protein binding sites or by a-direct action on renal function.
Although their body weights were decreased by about 77% and their brain weights by about 30%, high-affinity [3H] muscimol binding to a cerebral membrane fraction was not altered in hereditary pituitary dwarf mice. Marked changes in the level of pituitary growth-associated hormones do not appear to be associated with a change in cerebral GABA-receptors.
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Glutamate decarboxylase (GAD) activities were determined in homogenates of 8 brain regions of mice that had been differentially housed ("isolated" vs "grouped") for 4--9 weeks. GAD activity was lower in whole forebrains and in olfactory bulbs of isolated mice, changes which might be associated with their increased aggressiveness.
Binding of [3H]GABA and [3H]muscimol, indicative of GABA-receptors, has been demonstrated in a neurone-enriched culture of embryonic mouse brain using a ligand-binding technique. Evidence is provided for the existence of different populations of GABA-receptors.
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"Specific" binding of [3H]muscimol (11.5 nM) related to GABA receptors, occurred in subcellular particles prepared from 4-, 8-, and 12-day cultures of embryonic (14- to 15-day-old) mouse cerebrum, but not to particles prepared from 20- to 45-day cultures. Phase-contrast microscopy revealed that the presence of neuronal elements (neuroblasts, neurites) paralleled the binding of [3H]muscimol. Further evidence is thus provided for using high-affinity [3H]muscimol binding as a "neuronal marker."
Muscimol has been used to increase our knowledge of central GABAergic systems, CNS physiology, and behavior. Some studies concerning the neurophysiological and behavioral effects of muscimol and its analogs have been reviewed and analyzed. In vivo iontophoretic studies have greatly increased our knowledge of the active conformation(s) adopted by GABA during its interaction with neuronal synaptic (or extrasynaptic) receptors, and behavioral studies have supported the notion that central GABAergic systems might be involved in convulsions, extrapyramidal functions, and other behaviors. However, behavioral studies with muscimol remain difficult to interpret in terms of central GABAergic systems, especially since muscimol is extensively metabolized and since it appears to interact with membrane sites other than GABA receptors. Muscimol does not appear to be useful for reversing human neurologic-psychiatric disorders.
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