Influence of intravenously administered catecholamines on cerebral oxygen consumption and blood flow in the rat

In order to study effects of catecholamines on cerebral oxygen consumption (CMRo₂) and blood flow (CBF), rats maintained on 75 % N₂O and 25 % O₂, were infused i.v. with noradrenaline (2, 5, or 8 μpg. kg^-1. min^-1) or adrenaline (2 or 8, μg. kg^-1.min^-1) for 10 min before CBF and CMR_oz were measured. In about 50% of animals infused with 2–8, μg. kg^-1 min^-1 of noradrenaline, CMRo_z (and CBF) rose. However, there was no dose-dependent response, and CMRo₂, did not exceed 150% of control. The effects of noradrenaline in a dose of 5 μg. kg^-l. min^-1 on CMRo₂, and CBF were blocked by propranolol (2.5μg.kg^-1). In animals infused with adrenaline (8 μg.kg^-1.min^-1) CMRo₂, was doubled and, in many, CBF rose 4- to 6-fold. It is concluded that, when given in sufficient amounts, catecholamines have pronounced effects on cerebral metabolism and blood flow, the effects of adrenaline on CMRo₂, and CBF resembling those observed in status epilepticus.