Hindquarter vasodilation after intracisternal injection of D-arginine in the conscious rat.

The cardiovascular effects of the centrally injected D-arginine were investigated in the conscious rat chronically instrumented with cisternal, arterial, and venous cannulae, as well as an electromagnetic flow probe around the superior mesenteric artery, renal artery, or terminal aorta (hindquarter). Intracisternal injection of D-arginine (10 mumol) increased arterial blood pressure and hindquarter flow lasting for 60 min or more. Previous injection of the beta-adrenoceptor blocker, propranolol (2 mg/kg, I.V.), markedly attenuated the hindquarter vasodilation caused by D-arginine; this response suggests the release of adrenaline. Peripheral resistance, calculated as arterial pressure divided by regional flow, increased in both the superior mesenteric artery (60%) and the renal artery (45%) 5 min after intracisternal injection of D-arginine. In the hindquarter, however, peripheral resistance decreased by 35% and arterial pressure increased by 25%. The pressor effect was significantly attenuated by producing ganglionic blockade with chlorisondamine (5 mg/kg, I.V.). The total peripheral blood flow increased from 12.9 to 15.9 ml/min/100 g body weight. This response indicates that the pressor effect of D-arginine is due to an increase of cardiac output rather than of peripheral resistance. Centrally administered D-arginine appears to activate the sympatho-adrenal system, especially the release of adrenaline.