COCAINE AND EXERCISE - PHYSIOLOGICAL-RESPONSES OF COCAINE-CONDITIONEDRATS

To compare the physiological response to a cocaine-exercise challenge in cocaine-conditioned animals with that of acute-cocaine animals, rat s were injected i.p. with either cocaine (20 mg.kg(-1)) or saline, twi ce daily for 14 consecutive days. On the 15th day (test day) cocaine-c onditioned rats received an i.v. injection of cocaine (5 mg.kg(-1)) (c hronic group). One-half of the chronic saline rats also received the c ocaine injection (acute group), while the other half received saline ( saline group). Immediately after injection, all rats were either reste d or exercised (22 m.min(-1), 10% grade) for 30 min. For most paramete rs there was no difference between the responses of the chronic and ac ute cocaine groups at rest or to the cocaine-exercise challenge. Durin g exercise, both cocaine groups had similarly higher lactate values th an the saline animals (P < 0.05). Both groups had similarly greater re ductions in glycogen content of the white and red vastus muscles than occurred in the saline group; and both groups had similar increases in corticosterone. In contrast, cocaine-conditioned animals had a greate r rise in norepinephrine (P < 0.059) and epinephrine (P < 0.001) in re sponse to cocaine-exercise than did the acute group. The mechanism res ponsible for the exaggerated catecholamine response in the chronic coc aine animals is unknown.