Rapid sensitization to the cardiovascular effects of cocaine in rats.

Effects of repeated daily administrations of cocaine on blood pressure and heart rate were studied in conscious rats. Cocaine (0.03-3.0 mg/kg i.v.) increased blood pressure and heart rate the first time it was administered (day 1) However, the magnitude and duration of the increases in blood pressure caused by cocaine (0.1-3.0 mg/kg) dramatically increased on day 2 and remained (except 1.0 mg/kg dose) at these levels through day 5. Following two drug-free days (days 6 and 7), the increase in blood pressure caused by cocaine (0.1, 0.3 and 3.0 mg/kg) on day 8 was still elevated. Unlike blood pressure, no enhancement in heart rate response to cocaine was observed.