title: [Modulation of 3,4-diaminopyridine-evoked norepinephrine release from rat hippocampal slices by activation of alpha 2-adrenoceptor].
abstract: The effects of the alpha 2-adrenoceptor agonist clonidine and antagonist yohimbine were investigated on 3,4-diaminopyridine(DAP)-evoked [3H]norepinephrine ([3H]NE) release from rat hippocampal slices in the presence and absence of extracellular Ca2+. The slices were preincubated with [3H]NE and superfused in the presence of desipramine 1 mumol.L-1.[3H]overflow was evoked by addition of DAP 100 mumol.L-1 for 10 min to the superfusion medium. Clonidine and yohimbine inhibited and enhanced the 3,4-DAP-evoked [3H]NE release in a concentration-dependent manner both in the presence and absence of extracellular Ca2+. The effect of yohimbine was abolished by clonidine and was additive with the effect of ruthenium red. In the presence of extracellular Ca2+ the clonidine effect was not altered by addition of omega-conotoxin GVIA 0.1 mumol.L-1 or by removal of extracellular Ca2+, suggesting that the Ca2+ entry was not involved in the modulatory mechanisms of DAP-evoked [3H]NE release by activation of alpha 2-receptor. In the absence of extracellular Ca2+ the clonidine effect was reduced by the presence of ruthenium red 10 mumol.L-1, supporting the hypothesis that alpha 2-adrenoceptor activation might affect the intracellular mechanism of Ca2+ homeostasis.
authors.affiliation: Shanghai Institute of Physiology, Chinese Academy of Sciences.
authors.forename: H Y
authors.initials: HY
authors.lastname: Huang
authors.forename: S P
authors.initials: SP
authors.lastname: Dai
authors.forename: P G
authors.initials: PG
authors.lastname: Xie
mesh_terms: D015761:4-Aminopyridine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000077770:Amifampridine; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology*; D006624:Hippocampus / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D010456:Peptides, Cyclic / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012430:Ruthenium Red / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology*; D020866:omega-Conotoxin GVIA
chemical_list: D002121:Calcium Channel Blockers; D010456:Peptides, Cyclic; D015221:Potassium Channels; D011942:Receptors, Adrenergic, alpha; D012430:Ruthenium Red; D015016:Yohimbine; D020866:omega-Conotoxin GVIA; D015761:4-Aminopyridine; D003000:Clonidine; D000077770:Amifampridine; D009638:Norepinephrine