title: Interaction between glutamate and GABA on 3H-noradrenaline release from rat hypothalamus.
abstract: Glutamate has been shown to stimulate noradrenaline (NA) release from hypothalamic nerve terminals. In the present study, we evaluated the possible interaction between the excitatory amino acid glutamate and gamma-aminobutyric acid (GABA), an inhibitory transmitter, on noradrenaline (NA) release from mediobasal hypothalamus (MBH) of adult male rats. Hypothalamic slices loaded in vitro with 3H-NA were superfused and exposed to glutamate, N-methyl-D-aspartic acid (NMDA), or kainate (KA). We found that 3H-NA release evoked by the excitatory amino acids glutamate and NMDA was dramatically decreased by GABA. The facilitatory effects of NMDA and KA were prevented concentration-dependently by the GABAB receptor antagonist 2-hydroxy saclofen which restored the NMDA effect. In addition, baclofen blocked K(+)-induced 3H-NA release. Activation of GABAA receptors by muscimol and THIP was ineffective. In conclusion, glutamate and GABA, through GABAB receptors, may interact to modulate NA release from the rat mediobasal hypothalamus.
authors.affiliation: Laboratorio de Investigaciones Cerebrales, LINCE-CONICET, Facultad de Ciencias Médicas, Mendoza, Argentina.
authors.forename: C E
authors.initials: CE
authors.lastname: Navarro
authors.forename: R J
authors.initials: RJ
authors.lastname: Cabrera
authors.forename: A O
authors.initials: AO
authors.lastname: Donoso
mesh_terms: D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D004347:Drug Interactions; D018755:GABA Agonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology*; D007031:Hypothalamus / Q000187:drug effects* / Q000378:metabolism; D007608:Kainic Acid / Q000494:pharmacology; D008297:Male; D016202:N-Methylaspartate / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014316:Tritium; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D018755:GABA Agonists; D014316:Tritium; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D016202:N-Methylaspartate; D001418:Baclofen; D011188:Potassium; D007608:Kainic Acid; D009638:Norepinephrine