COCAINE POTENTIATES THE BLOOD-PRESSURE AND CEREBRAL BLOOD-FLOW RESPONSE TO NOREPINEPHRINE IN RATS

Acute drug-induced hypertension is known to have adverse consequences on the cerebral vasculature. Cocaine abuse has been reported to be ass ociated with an increased frequency of hemorrhagic or ischemic stroke. The purpose of this study was to determine whether cocaine alters the blood pressure or cerebral blood flow response to exogenous norepinep hrine. A craniectomy was made over the parietal cortex in rats and cor tical blood flow changes were measured using laser-Doppler flowmetry. Ten minutes after cocaine (1 mg/kg, i.v.) or saline, increasing doses of norepinephrine (0.01-10 mu g/kg, i.v.) were given by bolus injectio n and changes in blood pressure and flow were monitored. Cocaine produ ced a transient 27+/-5% increase in blood pressure and a 38+/-9% incre ase in blood flow. Cocaine significantly potentiated the blood pressur e and cerebral blood flow responses produced by submaximal presser dos es of norepinephrine (0.01-0.6 mu g/kg, i.v.). In summary, cocaine cau ses a rapid, transient increase in blood pressure and cortical blood f low and potentiates the magnitude and duration of the pressure and flo w response to norepinephrine. Repetitive blood pressure elevations in cocaine abusers is one of the proposed mechanisms leading to damage of cerebral vessels. These results may be relevant to an increased frequ ency of cerebrovascular accidents in cocaine-abusing individuals.