The effect of dopamine on blood flow in skeletal muscles.

To explain some mechanisms of the peripheral action of dopamine experiments were carried out on anesthetized rabbits in which the blood flow in calf muscles was measured during rest and during evoked twitches, using the method of 133Xe clearance of Lassen et al.; the arterial blood pressure and ECG were simultaneously recorded. Dopamine reduced the blood flow, particularly after a muscular effort. That effect of dopamine was not blocked by the alpha- and beta-adrenoceptor antagonists phentolamine and propranolol, the dopamine receptor antagonist haloperidol, or by the agent blocking sympathetic nerve endings compound BW392C60. Only low doses of dopamine given after propranolol pretreatment caused an increase in the blood flow. Dopamine depressed the arterial blood pressure, particularly the diastolic one. Pretreatment with phentolamine and haloperidol did not antagonize that effect, while pretreatment with propranolol or BW392C60 abolished or reversed the action of dopamine. The depression by dopamine of the blood flow in an important area of skeletal muscles indicates that part of the circulating blood may be shifted to other vascular beds, e.g. to the viscero - renal one.