1981 Volume 3 Issue 3 Pages 318-325
Dopamine, which is known to raise systemic blood pressure by stimulating alpha and beta-adrenergic receptors, also causes vasodilatation of the kidney and other organs by stimulating the specific dopamine receptors. It has been demonstrate in animals that either dopamine or dopamine agonist leads to cerebral vasodilatation, witch is blocked by its antagonists. These findings suggest that the specific dopamine receptors may exist in the cerebral arteries of certain animals. However, effects of dopamine on cerebral blood flow (CBF) is still obscure in human. The present study was performed in this respect.
The subjects comprised of 11 patiants with ischemic cerebrovascular diseases and 3 patients with degenertive diseases. The CBF was measured by the Argon inhalation method before and during intravenous administration of dopamine. Argon gas tension of arterial and internal jugular venous blood was continuously moniterd using the mass-spectrometer, and CBF was calculated by desaturation curve using the Fick princilpe. Dose-responses to dopamine were investigated in 6 subjects and autoregulation of CBF was examined by head-up tilting in 8 cases before and during dopamine.
The CBF was significantly increased from 41.3±7.9 (ml/100 g brain/min) to 46.1±8.9 (12% increase) after intravenous infusion of dopamine at a rate of 2μg/kg·min. Mean values for cerebral oxygen consumption before and after dopamine administration were 2.77±0.77, and 2.85±0.66 (ml/100 g brain/min), respectively, indicating that the drug had no significant effect on cerebral metabloism. During dopamine administration mean arterial blood pressure was slightly lowered and cerebrovascualr resistance was significantly reduced from 2.46±0.54 (mmHg/ml/100 g brain/min) to 2.15±0.51, although arterial blood gases and pH remained unchanged. Dopamine-induced 10% increase in CBF was not altered by changing infusion rate from 1 to 4 μg/kg · min but slightly reduced by high dose administration (8 μg/kg · min). On the other hand, autoregulation of CBF was not affected by dopamine.
The results suggest that small doses of dopamine may exert a direct vasodilating action on the cerebral arteries by stimulation of the specific dopamine receptors.
