An in vivo electroanalytic method was used to measure dopamine and dopamine metabolite levels in the anterior caudate of freely behaving cats. Food reinforcement was made contingent on either increasing or decreasing dopamine metabolite levels. The cats were found to be capable of contingent metabolite level variation in accord with reinforcement contingency. The metabolite variations were observed as both short-term and long-term changes, and were significantly different than variations obtained during random reinforcement. No distinctive overt behavioral responses were observed to accompany any of the reinforcement conditions. These results indicate that central dopaminergic activity can be significantly altered through extrinsic control and further imply that specific stimulus environments may contribute to the regulation and/or disregulation of neurochemical brain systems.