Effects of dopamine on the conductance of perfused vascular beds of the chloralosed cat

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Abstract
1 Dopamine produced vasoconstriction followed by secondary vasodilatation in the perfused cat hindquarters and splanchnic region. Low doses produced only vasodilatation in the splanchnic region. 2 Phenoxybenzamine abolished, while desipramine and cocaine potentiated, the vasoconstrictor and secondary dilator actions of dopamine. 3 After phenoxybenzamine, dopamine produced only vasodilatation in both the hindquarters and splanchnic region, being more effective in the latter. 4 Haloperidol, but not propranolol, atropine or mepyramine, antagonized dopamine-induced vasodilatation. 5 Dopamine differs from other catecholamines in that, while its cardiac effects are mediated by a β-adrenoceptive mechanism, its vasodilator effects are not. 6 The results support the concept of a specific receptor mediating dopamine vasodilatation.