Document Detail


In vivo release of newly synthesized [3H]GABA in the substantia nigra of the rat: relative contribution of GABA striato-pallido-nigral afferents and nigral GABA neurons.
MedLine Citation:
PMID:  1794098     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The release of [3H]gamma-aminobutyric acid ([3H]GABA) continuously formed from [3H]glutamine has been measured with a push-pull cannula implanted in the substantia nigra of the rat anesthetized with ketamine. Consistent with the high density of GABA terminals coming from both the striato-pallido-nigral afferents, and from GABA nigrofugal neurons, our results showed that a large amount of [3H]GABA was spontaneously released in the reticulata, about 4 times higher than in the compacta. In the absence of calcium the spontaneous [3H]GABA release was reduced (-30%), as well as the K(+)-induced release of [3H]GABA (-66%). Bicuculline (10(-4) M) did not affect the K(+)-evoked release of [3H]GABA, suggesting that autoreceptors on GABA afferent fibers are distinct from the GABAA subtype. Partial lesions of striato- and pallido-nigral GABA neurons with kainic acid (1.2 micrograms) decrease by 40% the glutamic acid decarboxylase (GAD) activity in the ipsilateral SN without decreasing the spontaneous release of [3H]GABA; even following extensive lesions with kainic acid (2.5 micrograms), GAD activity (-72%) and spontaneous [3H]GABA release (-83%) were not completely abolished. These results suggest that a non-negligible contribution of GABA nigral neurons accounts for the spontaneous GABA release measured in the substantia nigra. This is further supported by the decrease (-20%), and the increase (+40%) of [3H]GABA release produced by the local application of glycine (10(-6) M), and bicuculline (10(-4) M), which respectively, inhibits and activates the nigral neuron activity. The contribution of nigral GABA neurons to the amount of [3H]GABA release from the substantia nigra, is likely linked to their high spontaneous firing rate.
Authors:
N Lantin le Boulch; N A Truong-Ngoc; C Gauchy; M J Besson
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Brain research     Volume:  559     ISSN:  0006-8993     ISO Abbreviation:  Brain Res.     Publication Date:  1991 Sep 
Date Detail:
Created Date:  1992-04-08     Completed Date:  1992-04-08     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0045503     Medline TA:  Brain Res     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  200-10     Citation Subset:  IM    
Affiliation:
Laboratoire de Neurochimie Anatomie, C.N.R.S., Université Pierre et Marie Curie, Paris, France.
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MeSH Terms
Descriptor/Qualifier:
Anesthesia
Animals
Bicuculline / pharmacology
Calcium / physiology
Corpus Striatum / physiology*
Globus Pallidus / physiology*
Glutamine / metabolism
Glycine / pharmacology
Kainic Acid / toxicity
Ketamine
Male
Nerve Endings / drug effects,  metabolism
Neurons / physiology*
Neurons, Afferent / physiology*
Potassium / pharmacology
Rats
Rats, Inbred Strains
Stereotaxic Techniques
Substantia Nigra / metabolism*,  physiology
gamma-Aminobutyric Acid / biosynthesis*,  physiology
Chemical
Reg. No./Substance:
485-49-4/Bicuculline; 487-79-6/Kainic Acid; 56-12-2/gamma-Aminobutyric Acid; 56-40-6/Glycine; 56-85-9/Glutamine; 6740-88-1/Ketamine; 7440-09-7/Potassium; 7440-70-2/Calcium

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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