Role of dendritic dopamine of the substantia nigra in the modulation of nigrocollicular gamma-aminobutyric acid release: in vivo studies in the rat.
The release of gamma-[3H]aminobutyric acid ([3H]GABA) newly synthesized from [3H]glutamine was estimated in the superior colliculus of ketamine-anesthetized rats superfused via a push-pull cannula. A significant amount of [3H]GABA was spontaneously released in the superior colliculus (582 +/- 49 pCi/10 min). A major part of the large K(+)-evoked increase of the [3H]GABA release was Ca2+ dependent. When neuronal activity of the substantia nigra was enhanced by nigral application of K+ (30 mM) or bicuculline (10(-4) M), a persistent increase of the collicular [3H]GABA release was observed (60 and 80%, respectively). Conversely, when nigral activity was reduced by nigral application of GABA (10(-4) M) or superfusion with a Ca(2+)-free medium, a sustained decrease of the collicular [3H]GABA release was observed (-30 and -40%, respectively). Following the nigral application of a selective D2-receptor agonist. RU 24926 (10(-6) M), for 30 min in 6-hydroxydopamine-lesioned rats, a phasic increase (60%) of the collicular [3H]GABA release was detected. This effect could result from an activation of nigrocollicular GABAergic neurons by D2-receptor stimulation, because nigral activity and collicular release of [3H]GABA changed in a parallel direction.
Laboratoire de Neurochimie Anatomie, CNRS, Université Pierre et Marie Curie, Paris, France.
N
N
Lantin Le Boulch
N A
NA
Truong-Ngoc
C
C
Gauchy
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D003712:Dendrites / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism / Q000502:physiology*; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D008297:Male; D009474:Neurons / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D010627:Phenethylamines / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects / Q000502:physiology; D013378:Substantia Nigra / Q000378:metabolism* / Q000502:physiology; D013477:Superior Colliculi / Q000378:metabolism / Q000502:physiology; D014316:Tritium; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D005971:Glutamates; D010627:Phenethylamines; D011954:Receptors, Dopamine; D014316:Tritium; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; C025254:RU 24926; D011188:Potassium; D004298:Dopamine; D001640:Bicuculline