Pharmacological characterization of postjunctional alpha-adrenoceptors in cerebral arteries from the sheep.
1. The responsiveness to noradrenaline was characterized in cerebral arteries from the sheep, since this species was large enough to permit a comparison of arteries from different parts of the cerebral vasculature. 2. Noradrenaline caused contraction of the basilar artery, middle cerebral artery and small pial arteries by stimulation of alpha 1-adrenoceptors. 3. The maximum contraction to noradrenaline was small in the basilar artery (28% of the 5-hydroxytryptamine (5-HT) maximum) but larger in the middle cerebral artery (78% of the 5-HT maximum) and pial artery (92% of the 5-HT maximum) of the sheep. 4. Cocaine (10 microM) potentiated noradrenaline-induced contractions in the sheep middle cerebral artery but not in the sheep basilar artery. 5. The noradrenaline contraction, relative to the 5-HT contraction, was not affected by removal of the endothelium in either the sheep basilar or middle cerebral artery. 6. The results showed a variation within the sheep cerebral vasculature in the response to noradrenaline which cannot be explained by regional differences in alpha-adrenoceptor subtypes, noradrenaline uptake mechanisms or endothelial function.
Gaw
A J
AJ
Department of Physiology and Pharmacology, University of Strathclyde, Glasgow.
Wadsworth
R M
RM
D000818:Animals; D001488:Basilar Artery / Q000187:drug effects; D002536:Cerebral Arteries / Q000187:drug effects; D003042:Cocaine / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology; D012756:Sheep
D011942:Receptors, Adrenergic, alpha; D012701:Serotonin; D003042:Cocaine; D009638:Norepinephrine