Acute cocaine administration alters posttraumatic blood pressure and cerebral blood flow in rats

Cocaine abuse is widespread, and it is possible that its two main pharmacological actions, sympathomimetic and local anesthetic, could influence the blood pressure and cerebral blood flow response to brain injury, which occurs with increased frequency in drug abusers. We tested this hypothesis in ventilated barbiturate-anesthetized rats. Brain injury was induced using the fluid-percussion method, and cortical blood flow was measured using laser-Doppler flowmetry. Saline, cocaine, methamphetamine, or lidocaine was administered 10 min before injury. Upon injury, both cocaine- and saline-pretreated rats showed a similar acute hypertensive phase, which was followed by a period of more pronounced hypotension in the cocaine group (68 +/- 4 vs. 100 +/- 6 mmHg). Cortical blood flow increased dramatically 3-15 s following injury-induced hypertension in both the cocaine and saline groups (approximately 230-260%), but then fell below preinjury values within minutes. At 1 h postinjury, the blood flow in the saline group was 53 +/- 6% of the preinjury value, while in the cocaine group, flow was 74 +/- 7% of preinjury baseline. Similar to the cocaine-treated animals, methamphetamine also caused a more pronounced hypotensive event, but blood flow was not significantly different from saline controls. Lidocaine did not alter posttraumatic blood pressure but did significantly elevate blood flow throughout the 1-h postinjury period. At 60 min posttrauma, blood flow in the lidocaine group was 80 +/- 10% of the preinjury value. The mechanism by which cocaine alters blood pressure and blood flow after injury is not entirely certain.(ABSTRACT TRUNCATED AT 250 WORDS)