Antagonism of bencianol (ZY 15051) and idazoxan (RX 781094) to norepinephrine in feline pial arteries in situ.
The anticonstrictor properties of the semisynthetic flavinoid compound bencianol (ZY 15051) and the highly selective alpha 2-antagonist idazoxan (RX 781094) were investigated in pial arteries (resting diameter 60-348 micron) in situ. Using micropuncture technique mock cerebrospinal fluid (CSF) containing the compounds was applied perivascularly, and vascular diameter was measured by means of image splitting. 1. Idazoxan and bencianol (10(-6)-10(-4) M) did not change vascular diameter per se. 2. The constriction (19%) elicited by K+-free mock CSF was not significantly altered by bencianol. 3. The norepinephrine (NE) (2.5 X 10(-3) M) induced constriction (25-28%) was dose dependently reduced by bencianol as well as idazoxan. Both agents had similar potency and maximal effects blocking the NE induced constriction at 10(-4) M each. It is concluded that the NE induced constriction of feline pial arteries in situ is mediated by postjunctional alpha 2-adrenoceptors. Considering the similarities of bencianol and idazoxan in the antagonism to NE an alpha 2-antagonistic action of bencianol appears possible.
Wahl
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D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001158:Arteries / Q000187:drug effects; D002415:Cats; D004146:Dioxanes / Q000494:pharmacology*; D004147:Dioxins / Q000494:pharmacology*; D005260:Female; D005419:Flavonoids / Q000494:pharmacology*; D019329:Idazoxan; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009638:Norepinephrine / Q000037:antagonists & inhibitors*; D011189:Potassium Chloride / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D004147:Dioxins; D005419:Flavonoids; D011189:Potassium Chloride; C047756:bencianol; D009638:Norepinephrine; D019329:Idazoxan