COCAINE AND EXERCISE - ALTERATION IN CARBOHYDRATE-METABOLISM IN ADRENODEMEDULLATED RATS

The combined treatment of cocaine-exercise (CE) causes an exaggerated catecholamine response, a rapid depletion of muscle glycogen, and accu mulation of lactic acid. To assess the contribution of the adrenal med ulla in the catecholamine response and to determine the role of epinep hrine (Epi) on carbohydrate metabolism, cocaine (20 mg/kg ip) or salin e was injected into sham-operated (Sham) or adrenodemedullated (AdM) r ats, which then ran for 5 min at 56 m/min, 0% grade. In Sham rats, CE caused plasma Epi values (means +/- SE) to rise to 27.7 +/- 6.9 nM com pared with 13.3 +/- 1.5 nM in saline-exercise (SE) and 0.8 +/- 0.2 nM in both AdM-CE and AdM-SE animals (P < 0.05). With minimal Epi in AdM, CE still caused glycogen to fall to lower levels (25.4 +/- 3.0 mu mol /g vs. 40.5 +/- 2.4 mu mol/g) and lactate to rise to higher levels (17 +/- 3 vs. 9 +/- 1 mmol/kg) in white vastus muscle than in SE group (P < 0.05). CE had no significant effect on soleus and red vastus glycog enolysis but it did cause lactate accumulation in red vastus. As a res ult, plasma lactate levels were also higher after CE compared with SE in AdM (17.9 +/- 2.0 vs. 8.5 +/- 0.5 mM, P < 0.05). We conclude that d uring CE 1) Epi is not essential to the alteration in carbohydrate met abolism; 2) the latter may be related to the other catecholamines; 3) the adrenal medulla is the only source of Epi; and 4) the adrenal medu lla is not the source of the increased levels of norepinephrine or dop amine.