Responses of pulmonary vasculature of cattle to dopamine and apomorphine |
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Authors: | F R BAKUNZI P EYRE |
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Institution: | Pharmacology Laboratory, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada |
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Abstract: | Both dopamine and apomorphine caused concentration-dependent contractions of the bovine pulmonary artery from rest. Both of these compounds caused relaxation of histamine-precontracted arterial and venous strips after α-adrenoceptor blockade. Arterial contraction elicited by dopamine was inhibited either by phentolamine (α-blocker) or by the dopamine-selective antagonists, spiperone and butaclamol. Apomorphine in the highest concentration (<10-5 M) inhibited dopamine-induced contractions. Dopamine- and apomorphine-induced vascular relaxations were attenuated by propranolol but not by spiperone or butaclamol. These data suggest that dopamine- and apomorphine-induced relaxation in these preparations is most likely mediated through β-adrenergic mechanisms, whereas dopamine-induced contractions seem to involve both α-adrenergic and dopa-minergic receptors. |
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