Amphetamine-induced increase in rat cerebral blood flow: apparent lack of catecholamine involvement.

The influence of D,L-amphetamine (5 mg/kg i.p.) on regional cerebral blood flow (CBF) in rats has been studied after surgically or pharmacologically induced depletion of brain catecholamines. (1) Bilateral removal of the superior cervical ganglion (one week before the experiment) did not prevent the amphetamine-induced augmentation of CBF present in intact animals to 2--4 times above the control value. Maximal changes occurred in the frontal and parietal cortex. (2) Destruction of the ascending noradrenergic pathways by uni- or bilateral injections of 6-hydroxydopamine, which decreased the noradrenaline (NA) level in the frontal cortex by 89%, was ineffective in abolishing the increase in CBF caused by the drug in the frontal cortex. (3) The involvement of other catecholaminergic systems was excluded by pretreatment of the rats with reserpine plus a-methyl-p-tyrosine which reduced the levels of NA, dopamine and adrenaline in the frontal cortex with 92, 97 and 99% respectively. Such treatment did not alter the effect of amphetamine on CBF in the frontal cortex. The results support the hypothesis that the action of amphetamine on CBF is not mainly mediated by catecholamines.