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J Appl Physiol 66: 377-383, 1989;
8750-7587/89 $5.00
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Journal of Applied Physiology, Vol 66, Issue 1 377-383, Copyright © 1989 by American Physiological Society

ARTICLES

Effect of various doses of cocaine on endurance capacity in rats

M. E. Bracken, D. R. Bracken, W. W. Winder and R. K. Conlee
Department of Physical Education, Brigham Young University, Provo, Utah 84602.

To determine the effects of a variety of doses of cocaine on endurance capacity, rats were injected intraperitoneally with either 0.1, 0.5, 2.5, 12.5, or 20 mg/kg body wt 20 min before running to exhaustion at 26 m/min up a 10% grade. Animals given saline ran 116 +/- 9 (SE) min. At doses of 12.5 and 20 mg/kg, cocaine reduced endurance time significantly (34 and 74%, respectively). At rest the drug had no effect on liver or fast-twitch muscle glycogen but significantly reduced (20-40%) soleus glycogen at the two highest doses. However, at exhaustion, the quantity of glycogen depleted in the fast-twitch red and white vastus muscles was similar in all groups despite the reduced run times of the animals receiving a higher dose implying a greater rate of glycogenolysis due to cocaine. Blood lactate in the 20 mg/kg group (9.9 +/- 1.2 mM) at exhaustion was nearly twice that of the saline controls at exhaustion (5.1 +/- 0.6). Before exercise plasma norepinephrine (at doses of 2.5, 12.5 and 20 mg/kg) was higher than saline controls and remained higher (20 mg/kg groups) at exhaustion. We conclude that high doses of cocaine cause rapid muscle glycogen depletion and early fatigue. The mechanism by which cocaine causes these effects is not clear.


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R. K. Conlee, K. P. Kelly, E. O. Ojuka, and R. L. Hammer
Cocaine and exercise: alpha -1 receptor blockade does not alter muscle glycogenolysis or blood lactacidosis
J Appl Physiol, January 1, 2000; 88(1): 77 - 81.
[Abstract] [Full Text] [PDF]


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