Effect of dopamine and apomorphine on bone circulation.

1. The effects of dopamine and apomorphine were studied on the nutrient artery perfusion pressure in dog tibia after constant--flow autoperfusion of the nutrient artery for femoral arterial blood. The carotid arterial pressure was also recorded. 2. Dopamine always induced a rise in nutrient artery perfusion pressure which was reduced or abolished, but never reversed, by alpha-blocking drugs. 3. Apomorphine only elicited a weak and inconstant decrease in the nutrient artery perfusion pressure. Apomorphine vasodilatation was not antagonized by haloperidol, alpha-blocking drugs, sympathetic denervation, propranolol, atropine or mepyramine. Apomorphine induced a non-specific relaxation of the intraosseous vasculature. 4. Thus, this study found with dopamine only a vasoconstrictor effect. These results found no evidence for the existence of dopaminergic receptors in the intraosseous vascular bed.