COCAINE AND EXERCISE - TEMPORAL CHANGES IN PLASMA-LEVELS OF CATECHOLAMINES, LACTATE, GLUCOSE, AND COCAINE

To determine the combined sympathoadrenal effects of cocaine and exerc ise in awake animals, rats were assigned to one of four treatment grou ps: saline-rest (SR), saline-exercise(SE), cocaine-rest (CR), and coca ine-exercise (CEI. Venous blood samples from jugular catheters were ob tained at -40, 0-4, 7, 10, 13, 16, 19, 26, and 36 min after intravenou s injection of cocaine (5 mg/kg) or saline and the simultaneous onset of a 16-min treadmill run (26 m/min, 10% grade). CE increased plasma e pinephrine (24.2 nM at 16 min), norepinephrine (28.0 nM at 10 min), an d lactate (11.2 mM at 4 min) to levels 2-5 times greater than either t reatment (SE and CR) alone (P < 0.05) and 11-35 times higher than SR. Blood glucose values were significantly depressed in CE (-33% vs. SE) but increased in CR (+26% vs. SR). Plasma cocaine peaked < 2 min after injection in both CR and CE, and the peak was 69% higher in CE (P < 0 .05); however, the plasma elimination half-life (12-14 min) was not di fferent. These results indicate that the combined effect of the two sy mpathoadrenal stimulants, exercise and cocaine, amplify the catecholam ine responses to levels far greater than when each stimulant is used a lone.