PREGNANCY ENHANCES COCAINE-INDUCED STIMULATION OF UTERINE CONTRACTIONS IN THE CHRONICALLY INSTRUMENTED RAT

OBJECTIVE: Our purpose was to test whether cocaine stimulates uterine activity in nonpregnant and pregnant rats. STUDY DESIGN: The carotid a rtery and jugular vein were chronically catheterized, and a microballo on probe was inserted into the uterine cavity of 15 pregnant and 14 no npregnant female rats. Conscious animals received a bolus dose of eith er cocaine or saline solution intravenously. Cardiovascular and uterin e contractile responses were studied. RESULTS: Cocaine (2.5 mg/kg) ind uced a marked increase in uterine activity and arterial blood pressure in both pregnant and nonpregnant animals without producing systemic t oxicity. The maximum change in uterine contractions was greater in the pregnant group than in the nonpregnant group, and blood pressure resp onses were transient in both. CONCLUSION: This study is the first demo nstration that cocaine stimulates the rat uterus in vivo, with a great er increase in contractions in pregnant compared with nonpregnant anim als. These differences are not related to the hemodynamic response or pharmacokinetic profile of cocaine.