Cardiovascular responses elicited during binge administration of cocaine

Cocaine use is often characterized by a repeated pattern of frequent administrations (binge) followed by periods of abstinence. The repeated binge administration of methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) alters cardiovascular function and the arterial pressure and heart rate responses elicited by these drugs. Whether repeated binges of cocaine similarly affect cardiovascular function and cardiovascular responsiveness is unknown. Radiotelemetry was used to record the cardiovascular responses elicited during three successive cocaine binges (5 mg/kg, t.i.d., for 4 days) in conscious, unrestrained rats. Each binge was separated by a 10-day cocaine-free period. The effects of cocaine administration on vascular reactivity and vasovagal, Bezold-Jarisch reflex function were also evaluated. The intravenous administration of cocaine increased both mean arterial pressure (MAP) and heart rate. The arterial pressure and heart rate responses elicited by cocaine, both within and between the binges, were remarkably similar. The arterial pressure and heart rate responses elicited by the intravenous administration of sodium nitroprusside, acetylcholine and phenylephrine before each binge and 10 days after the last binge were not altered after the binge administration of cocaine. Likewise, Bezold-Jarisch reflex function elicited by intravenous serotonin was unchanged after the binge administration of cocaine. These results indicate that the administration of cocaine using this repeated binge model does not alter the arterial pressure and heart rate responses elicited by the drug, nor does it alter the cardiovascular responses elicited by a variety of vasoactive substances.