The influence of some vasoactive drugs on bone circulation.

We have studied the effect of various drugs on the intramedullary pressure in dog tibia after constant-flow autoperfusion of the nutrient artery by femoral arterial blood. The perfusion pressure and carotid arterial pressure were also recorded. Isoprenaline, acetylcholine, histamine, theophylline always lowered the perfusion pressure but had a variable effect on intramedullary pressure. This results from several factors e.g., perfusion pressure and intraosseous vasomotoricity. Adrenaline always caused a rise of the perfusion pressure and lowered the intramedullary pressure in most of the cases. Such effects were reduced or suppressed by alpha-blocking drugs. Isoprenaline caused a lowering of the perfusion pressure which was suppressed by propranolol. A rise of the intramedullary pressure through beta-induced vasodilatation was shown in some experiments. The effect of adrenaline on the perfusion pressure could be reversed after alpha-blockade. These results show the presence of intraosseous vascular alpha- and beta-adrenoceptors.