In vivo tonic modulation of the noradrenaline release in the rat cortex by locus coeruleus somatodendritic alpha(2)-adrenoceptors.
The regulation of noradrenaline release in the rat cingulate cortex by somatodendritic alpha(2)-adrenoceptors placed in the locus coeruleus was evaluated by dual-probe microdialysis. The alpha(2)-adrenoceptor antagonists BRL44408 (2-[2H-(1-methyl-1,3-dihydroisoindole)methyl]-4,5-dihydroimidazole), RS79948 ((8,12,13)-decahydro-3methoxy-12-(ethylsulphonyl)-6H-isoquino[2,1-g][1,6]-naphthyridine) and RX821002 (2-methoxyidazoxan) administered by reverse dialysis into the locus coeruleus increased concentration-dependently (0.01-100 microM) noradrenaline release in the cortex (maximal effects 170+/-30%, 543+/-17%, 195+/-26%, respectively). Administration of the alpha(2)-adrenoceptor antagonist idazoxan increased at lower (0.1-10 microM) but decreased at the highest dose (100 microM) noradrenaline in the cortex. These data demonstrate that somatodendritic alpha(2)-adrenoceptors in the locus coeruleus exert an inhibitory tonic modulation on noradrenaline release in noradrenergic terminal areas.
Fernández-Pastor
Begoña
B
Department of Pharmacology, University of the Basque Country, E-48940, Leioa, Bizkaia, Spain.
Meana
J Javier
JJ
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D003712:Dendrites / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006179:Gyrus Cinguli / Q000187:drug effects / Q000378:metabolism*; D019329:Idazoxan / Q000031:analogs & derivatives / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D054833:Isoindoles; D007546:Isoquinolines / Q000494:pharmacology; D008125:Locus Coeruleus / Q000378:metabolism*; D008297:Male; D017551:Microdialysis; D009287:Naphthyridines / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018341:Receptors, Adrenergic, alpha-2 / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D000317:Adrenergic alpha-Antagonists; D007093:Imidazoles; D007211:Indoles; D054833:Isoindoles; D007546:Isoquinolines; D009287:Naphthyridines; C104875:RS 79948-197; D018341:Receptors, Adrenergic, alpha-2; C058525:2-methoxyidazoxan; D009638:Norepinephrine; D019329:Idazoxan; C072125:BRL 44408